Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “neuron”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1976

Neuronal stimulation of (3H)thymidine incorporation by primary cultures of highly purified non-neuronal cells.

A specific intercellular interaction has been demonstrated between neuronal and non-neuronal cells that appears to increase the rate of non-neuronal cell proliferation. Isolated and recombined primary cultures of both cell types were prepared from 11-day embryonic chick sympathetic ganglia by a method recently developed in this laboratory. When non-dividing neurons were added to an equal number of proliferating non-neuronal cells, the amount of [methyl-3H]thymidine incorporated by these mixed cultures was 230% greater than that incorporated by 99% pure non-neuronal cultures. Removal of all neurons from such non-neuronal cultures by a 48-h preincubation without nerve growth factor resulted in an even greater increase in [3H]thymidine incorporation upon addition of neurons (370%). When increasing numbers of isolated neurons were added to non-neuronal cell cultures, the amount of [3H]thymidine incorporation initially increased in a dose-dependent fashion until it reached a plateau. In contrast, the addition of increasing numbers of non-neuronal cells to a constant number of neurons resulted in a linear increase in [3H]thymidine incorporation. In some cases neurons and non-neuronal cells were not grown in direct physical contact but were only allowed to communicate with one another through the culture medium. Such indirect communication never resulted in a stimulation of [3H]thymidine incorporation. When neurons were added to cultures of embryonic chick fibroblasts, the neurons grew well but did not stimulate [3H]thymidine incorporation by the fibroblasts. These results suggest that embryonic sympathetic neurons selectively stimulate the proliferation of non-neuronal cells derived from the same source.

Animals↗
PubMed1995

Somatostatin neurons are a subpopulation of GABA neurons in the rat dentate gyrus: evidence from colocalization of pre-prosomatostatin and glutamate decarboxylase messenger RNAs.

The distribution and extent of glutamate decarboxylase 65 (GAD65) mRNA-labeled neurons that coexpress pre-prosomatostatin mRNA were studied in the rat dentate gyrus of the dorsal and ventral hippocampal formation. The distribution of each group of neurons was determined initially by nonradioactive in situ hybridization experiments with digoxigenin-labeled riboprobes for GAD65 mRNA and pre-prosomatostatin mRNA. Double labeling experiments were then conducted with digoxigenin-labeled riboprobes for GAD65 mRNA and 35S-labeled riboprobes for pre-prosomatostatin mRNA. In the dorsal and ventral dentate gyrus, GAD65 mRNA-containing neurons were highly concentrated in the hilus and in the innermost part of the granule cell layer whereas only a few labeled neurons were scattered in the molecular layer. Pre-prosomatostatin mRNA-containing neurons were primarily located in the hilus and were virtually absent from the molecular and granule cell layers. The simultaneous detection of GAD65 and pre-prosomatostatin mRNAs in the same sections showed that the vast majority of pre-prosomatostatin mRNA-containing neurons in the hilus of the dentate gyrus were also labeled for GAD65 mRNA. In contrast many GAD65 mRNA-labeled neurons did not contain pre-prosomatostatin mRNA. These included all neurons in the molecular layer, neurons within the inner granule cell layer and neurons interspersed amongst double labeled neurons in the hilus. Quantitative analyses indicated that a very high percentage of hilar pre-prosomatostatin mRNA-containing neurons coexpressed GAD65 mRNA in the dorsal (96%) and ventral (92%) dentate gyrus. In contrast only a part of the total population of hilar GAD65 mRNA-containing neurons were also labeled for pre-prosomatostatin mRNA in the dorsal (43%) and ventral (53%) dentate gyrus. In the CA3c region, the percentages of neurons containing both mRNAs were similar to those observed in the hilus. The findings demonstrate that the vast majority of hilar somatostatin neurons, which have previously been shown to be extremely vulnerable to ischemia and seizure-induced damage, are GABA neurons. However, the total population of GAD65 mRNA-containing neurons in the hilus is substantially larger than the somatostatin-containing subgroup, and these findings reinforce the suggestion that GABA neurons are a major component of the diverse group of neurons in the hilus of the dentate gyrus.

Animals↗
PubMed2001

Converging and diverging cholinergic inputs from submucosal neurons amplify activity of secretomotor neurons in guinea-pig ileal submucosa.

The organization of synaptic connections between guinea-pig ileal submucosal neurons was examined using intracellular recordings from single or pairs of submucosal neurons. Synaptic inputs were elicited by stimulating cholinergic neurons using pressure-pulse application of 5-hydroxytryptamine (5-HT) in ganglia adjacent to those where intracellular recordings were obtained. In addition, when pairs of intracellular recordings were obtained, one neuron was activated by intracellular stimulation and synaptic responses were recorded in the other neuron. Neurobiotin-filled microelectrodes were employed to characterize cells electrophysiologically and immunohistochemically. Recordings were obtained from 176 (173 S-type and three AH-type) neurons; 81% of cells were classified as vasoactive intestinal peptide (VIP) neurons. No fast excitatory postsynaptic potentials and only rare slow excitatory postsynaptic potentials were recorded following intracellular stimulation of paired S-type neurons. However, when paired intracellular recordings were obtained from neurons within the same ganglion and 5-HT was applied to an adjacent ganglion, this stimulation evoked synchronized fast excitatory postsynaptic potentials in 94% of pairs. In contrast, when cell bodies of VIP-VIP pairs were located in different ganglia, fast synaptic activation evoked by 5-HT stimulation was not synchronized in 87% of pairs. When intracellular recordings were obtained from a single neuron and two separate ganglia were stimulated by 5-HT pressure-pulse activation, fast excitatory postsynaptic potentials originating from both sources were recorded in the same VIP neuron. Morphological study of 34 S-type and three AH-type horseradish peroxidase-labeled neurons was conducted. AH-type neurons had multiple axonal branches with dense arborization of collaterals containing numerous varicosities in three to nine ganglia, whereas axons of S-type neurons exhibited relatively rare collaterals and varicosities within adjacent ganglia. These results demonstrate that cholinergic neurons provide both diverging and converging inputs to VIP neurons, providing a mechanism to enhance activation of VIP secretomotor neurons. The axonal projections of AH-type neurons suggest they are likely candidates to provide diverging inputs to multiple VIP neurons.

Animals↗
PubMed2001

Indirect actions of bradykinin on neonatal rat dorsal root ganglion neurones: a role for non-neuronal cells as nociceptors.

1. In this study we have investigated the action of bradykinin (Bk) on cultured neonatal rat dorsal root ganglion (DRG) cells, with the aim of elucidating whether the neuronal response to Bk is influenced by association with non-neuronal satellite cells. 2. Bradykinin (100 nM) evoked an inward current (I(Bk)) in 51 of 58 voltage clamped DRG neurones (holding potential (V(h)) = -80 mV) that were in contact with non-neuronal satellite cells. 3. Bradykinin failed to evoke an inward current in isolated DRG neurones (V(h) = -80 mV) that were not in contact with non-neuronal satellite cells (n = 41). 4. The lack of neuronal response to Bk was not influenced by time in culture. Bradykinin failed to evoke a response in isolated neurones through 1-5 days in culture. By contrast neurones in contact with satellite cells responded to Bk throughout the same time period. 5. Failure of isolated neurones to respond to Bk was not due to the replating procedure or to selective subcellular distribution of receptors/ion channels to the processes rather than the somata of neurones. 6. Using Indo-1 AM microfluorimetry Bk (100 nM) was demonstrated to evoke an intracellular Ca(2+) increase (Ca(Bk)) in DRG neurones in contact with non-neuronal satellite cells and in isolated neurones. 7. These data suggest that the inward current response to Bk requires contact between DRG neurones and non-neuronal satellite cells. This implies an indirect mechanism of action for Bk via the non-neuronal cells, which may perform a nociceptive role. However, Bk can also act directly on the neurones, since it evokes Ca(Bk) in isolated neurones. The relationship between Ca(Bk) and the Bk-induced inward current is unknown at present.

Animals↗
PubMed2005

Seasonal change in neuron size and spacing but not neuronal recruitment in a basal ganglia nucleus in the avian song control system.

Neural plasticity in the song control system of seasonally breeding songbirds accompanies seasonal changes in singing behavior. The volume of Area X, a song control nucleus that forms a portion of the avian basal ganglia, is 75% larger in the spring than it is in the fall. The neuronal basis of the seasonal plasticity in Area X is largely unknown, however. We examined neuronal attributes of Area X in wild adult male song sparrows (Melospiza melodia) captured during the spring and the fall after being implanted for 30 days with osmotic pumps containing [3H]thymidine. We measured the volume of Area X from thionin-stained sections, and neuronal density and number, and average area of the soma from sections labeled with an antibody against Hu, a neuron-specific protein. We sampled two neuron classes: "small" neurons that were most likely striatal-like spiny neurons and "large" neurons, which most likely included pallidal-like projection neurons. We also analyzed seasonal patterns of neuronal recruitment to Area X. The average area of the soma and neuronal spacing for both neuronal classes were greater in breeding birds. There was no difference in total neuron number for both neuronal classes between seasons. The average area of the soma and density and number of newly recruited neurons did not vary across seasons. These results demonstrate that seasonal plasticity in Area X includes changes in neuron size and neuronal density, but not changes in the rate at which new neurons are recruited.

Animals↗
PubMed1984

Non-neuronal cell conditioned medium stimulates peptidergic expression in sympathetic and sensory neurons in vitro.

Regulation of peptide neurotransmitter metabolism was examined in dissociated cell cultures of neonatal rat sympathetic and sensory ganglia. Previous studies have shown that pineal gland conditioned medium (PCM) influences substance P (SP) and somatostatin (SS) metabolism in sympathetic neurons in vitro. The present study examines mechanisms mediating these effects, and compares the actions of PCM on sympathetic and sensory neurons. PCM treatment increased SP levels in a dose-dependent manner without altering SS content of sympathetic neurons cultured in the presence of ganglion non-neuronal cells. Conversely, treatment of pure sympathetic neuron cultures resulted in a dose-dependent increase in SS, while SP was virtually undetectable at all doses. By contrast, dorsal root ganglion, trigeminal ganglion, and nondose ganglion sensory neurons contained SP both in the presence and absence of ganglion non-neuronal cells. Moreover, in each of these neuronal populations treatment with PCM increased SP levels both in the presence and in the absence of ganglion non-neuronal cells. These observations suggest that ganglion non-neuronal cells are necessary for sympathetic but not sensory neuron expression of SP. Moreover, PCM apparently stimulates SP in neurons which already contain the peptide, but the factor cannot foster de novo expression of the phenotype. PCM also influenced other transmitter traits in sympathetic neurons, suggesting linkage between mechanisms regulating peptides and other transmitters. In cultures containing both sympathetic neurons and non-neuronal cells, PCM treatment increased cholineacetyltransferase (CHAC) activity as well as SP, and decreased tyrosine hydroxylase (TOH) activity. By contrast, PCM treatment of pure sympathetic neuron cultures led to parallel increases in SS and TOH activity with negligible levels of SP and CHAC. These observations suggest that in sympathetic neurons, SS may be linked with noradrenergic expression, while SP is associated with cholinergic development, although more data are required to confirm this relationship. Moreover, there may be a reciprocal relationship between SP and SS expression by sympathetic neurons analogous to previous observations regarding cholinergic-noradrenergic expression (P. H. Patterson and L. L. Y. Chun, Proc. Natl. Acad. Sci. USA 71, 3607-3610, 1974; Dev. Biol. 56, 263-280, 1977). Consequently, neurotransmitter phenotypic expression is a complex process in which the environment regulates a balance among multiple transmitters.

Animals↗
PubMed2000

Basic fibroblast growth factor (bFGF) acts on both neurons and glia to mediate the neurotrophic effects of astrocytes on LHRH neurons in culture.

Luteinizing hormone-releasing hormone (LHRH) neurons play a pivotal role in the neuroendocrine control of mammalian reproduction. Astrocytes were shown to be involved in the regulation of LHRH neuronal function, but little is known about the contribution of astroglial-derived factors in the regulation of LHRH neuron development. In order to gain insight into the mechanisms regulating the development of these cells, at morphological and biochemical levels we characterized the neurotrophic effects exerted by young astrocytes (maintained in culture for 8 days in vitro) and old astrocytes (maintained 26 days) on the differentiation, proliferation, and phenotypic expression of immortalized hypothalamic LHRH (GT(1-1)) neurons in vitro. Culturing GT(1-1) cells in the presence of young glia for different time intervals caused a marked acceleration in the acquisition of their neuronal phenotype. At all times examined, GT(1-1) cells cocultured with young glia exhibited a significantly greater extension of processes/cell, larger number of processes/cell and greater surface area of growth cones than GT(1-1) cells grown over nonglial adhesive substrates (polylysine). By contrast, when GT(1-1) neurons were cocultured with old glia, the length of neuronal processes and the growth cone surface area were significantly lower than in control GT(1-1) neurons cultured in the absence of glia. At 3 days in vitro (DIV), GT(1-1) neurons cocultured with young glia exhibited a 50% lower incorporation of [(3)H]thymidine than GT(1-1) neurons cultured without glia. By contrast, in the presence of old glia [(3)H]thymidine incorporation was significantly higher in cells cocultured with glia than in GT(1-1) neurons cultured alone. Localization of the proliferating cells by dual immunohistochemical staining revealed that the incorporation of bromodeoxiuridine (BrdU) was restricted to nuclei of GT(1-1) neurons when these were cocultured with young glia, but associated with both neurons and astrocytes in the presence of old glia. At the functional level, coculture of GT(1-1) neurons with young glia increased the spontaneous release of LHRH as compared to GT(1-1) neurons grown in the absence of glia. By contrast, in the presence of old glia LHRH release in the medium was significantly lower than in controls. Conditioned medium of young glia (ACM-Y) induced significant neurotrophic and functional effects on GT(1-1) cells, but these effects were 50% less potent than the coculture itself. Heat denaturation of ACM-Y totally abolished its neurotrophic and functional properties, indicating that they involved a peptide factor. Suppression of bFGF activity in ACM-Y reduced its neurotrophic activity by approximately 40%, but did not affect its LHRH release-promoting effects. By contrast, neutralization of endogenous bFGF activity in GT(1-1) neurons cocultured with young glia counteracted both neurotrophic and functional effects of young glia. Treatment of old glia with bFGF rescued its neurotrophic and functional effects on GT(1-1) cells. Moreover, the ACM of aged bFGF-treated old glia was the most powerful neurotrophic stimulus for GT(1-1) neurons. These results suggest that: 1) soluble peptidic factors, including bFGF, and mechanism(s) requiring coculture are responsible for the highly potent neurotrophic and functional effects of young glia; 2) the inhibitory effects of old glia on neurite outgrowth and LHRH release are mediated in part by soluble inhibitory molecules and in part by factors requiring coculture with old glia; 3) old glia may revert to a growth-supporting state when treated with bFGF and this functional shift involves a diffusible molecule with potent neurotrophic and functional effects on immortalized LHRH neurons. (c) 2000 Wiley-Liss, Inc.

Animals↗
PubMed1995

Spinal projection neurons to the laterodorsal pontine tegmental nucleus: relationship to preganglionic neurons and nitric oxide synthase.

The region of the rat sacral parasympathetic nucleus (SPN) contains distinct subpopulations of neurons that project supraspinally or are preganglionic neurons. Some preganglionic neurons in the SPN serve as the motor outflow for urinary bladder contraction; other neurons in the SPN project to regions of the rostral pons that subserve micturition reflexes. Previous studies utilizing immunohistochemistry or staining for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) have demonstrated that numerous neurons in the SPN contain nitric oxide synthase (NOS), the enzyme for nitric oxide synthesis. Thus, the objectives of this study were to determine 1) the distribution of neurons in the region of the SPN that project to the laterodorsal tegmentum (LDT) of the pons, 2) whether spinal neurons projecting to a peripheral autonomic ganglion also project to the LDT, and 3) whether NOS or NADPH-d is present in LDT projection neurons. Preganglionic neurons were identified by injecting the retrograde tracer fluorogold (FG) into the major pelvic ganglion (MPG). Supraspinally projecting neurons were identified by injecting the retrograde tracer fast blue (FB) into the LDT. Numerous FB-labeled neurons were present in the ipsi- and contralateral SPN and were immediately dorsal to FG-labeled preganglionic neurons. Neurons containing both tracers were not observed. Approximately 20% of preganglionic neurons, but no LDT projection neurons, were reactive for NOS and NADPH-d. These data suggest that the region of the SPN is a site for distinct subpopulations of neurons that project to the LDT and to the MPG and that NOS is contained in some preganglionic neurons, but is not a marker for LDT projection neurons.

Amidines↗
PubMed1995

Relationship of the time of origin and death of neurons in rat somatosensory cortex: barrel versus septal cortex and projection versus local circuit neurons.

The birth of a neuron initiates a series of ontogenetic events, e.g., neuronal migration and differentiation. The outcomes of these events are neurons that successfully integrate into the cortical circuitry and neurons that are unsuccessful and ultimately die. The present study determined whether there is a relationship between the generation and death of cortical neurons. The decrease in the density of postmigratory neurons (heavily labeled by a single injection of [3H]thymidine) during normal development was used as an index of neuronal death. The survival indices of neurons varied with their times of origin. Neurons born from gestational day (G) 15 to G18 had the highest rates of survival. In contrast, the earliest and latest generated neurons (i.e., those born on G12-G13 and those born on G19-G21, respectively) had the lowest survival rates. The role of neuronal death in the formation of cortical patterns was determined by assessing the survival of neurons in the barrels and septa of somatosensory cortex. No differences in the survival index were determined for neurons in the C-row barrels and adjacent septa with a particular time of origin. The survival rate of projection and local circuit neurons was determined with a double-labeling technique. One label, [3H]thymidine, was used to determine the time of origin of the neurons. The second label was used to identify the chemical or hodological characteristics of a neuron; projection neurons were labeled either by retrograde transport of horseradish peroxidase or by glutamate immunohistochemistry, and local circuit neurons were immunohistochemically identified with an antibody directed against gamma-aminobutyric acid (GABA) antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Bulbospinal neuropeptide Y-immunoreactive neurons in the rat: comparison with adrenaline-synthesising neurons.

Immunohistochemistry and retrograde tracing using cholera toxin B subunit colloidal gold (CTB-gold) has been used to identify neurons in the medulla that contain neuropeptide Y and project to the area of the intermediolateral cell column in either the upper (T2-T4) or the lower (T8-T9) thoracic spinal cord. The rostrocaudal distributions of neuropeptide Y neurons and neuropeptide Y/CTB-gold neurons have been compared with the distributions of adrenaline-synthesising, phenylethanolamine N-methyltransferase-containing neurons and phenylethanolamine N-methyltransferase/CTB-gold neurons visualised in adjacent sections. In particular areas of the rostral medulla similarities in the numbers and distributions of neuropeptide Y neurons and phenylethanolamine N-methyltransferase neurons suggested a coexistence of the peptide within the catecholamine neurons. However, at the most rostral levels of the rostral ventral medulla, the large numbers of phenylethanolamine N-methyltransferase neurons were not matched by similar numbers of neuropeptide Y neurons, so that the phenylethanolamine N-methyltransferase neurons in this area could not all contain neuropeptide Y. In the rostral ventral medulla fewer neuropeptide Y/CTB-gold neurons than phenylethanolamine N-methyltransferase/CTB-gold neurons were observed, so that these bulbospinal peptide neurons might define a subset of the phenylethanolamine N-methyltransferase/CTB-gold neurons, accounting for 25% of the total phenylethanolamine N-methyltransferase bulbospinal projection from the rostral ventral medulla. Other neuropeptide Y/CTB-gold neurons in the dorsal medulla are also likely to contain phenylethanolamine N-methyltransferase. Finally, a population of neuropeptide Y/CTB-gold neurons was identified in the caudal ventral medulla, these neurons appear not to contain catecholamine synthesising enzymes.

Animals↗
PubMed1988

Neuron-glia cell adhesion molecule interacts with neurons and astroglia via different binding mechanisms.

The neuron-glia cell adhesion molecule (Ng-CAM) is present in the central nervous system on postmitotic neurons and in the periphery on neurons and Schwann cells. It has been implicated in binding between neurons and between neurons and glia. To understand the molecular mechanisms of Ng-CAM binding, we analyzed the aggregation of chick Ng-CAM either immobilized on 0.5-micron beads (Covaspheres) or reconstituted into liposomes. The results were correlated with the binding of these particles to different types of cells as well as with cell-cell binding itself. Both Ng-CAM-Covaspheres and Ng-CAM liposomes individually self-aggregated, and antibodies against Ng-CAM strongly inhibited their aggregation; the rate of aggregation increased approximately with the square of the concentration of the beads or the liposomes. Much higher rates of aggregation were observed when the ratio of Ng-CAM to lipid in the liposome was increased. Radioiodinated Ng-CAM on Covaspheres and in liposomes bound both to neurons and to glial cells and in each case antibodies against Ng-CAM inhibited 50-90% of the binding. Control preparations of fibroblasts and meningeal cells did not exhibit significant binding. Adhesion between neurons and glia within and across species (chick and mouse) was explored in cellular assays after defining markers for each cell type, and optimal conditions of shear, temperature, and cell density. As previously noted using chick cells (Grumet, M., S. Hoffman, C.-M. Chuong, and G. M. Edelman. 1984 Proc. Natl. Acad. Sci. USA. 81:7989-7993), anti-Ng-CAM antibodies inhibited neuron-neuron and neuron-glia binding. In cross-species adhesion assays, binding of chick neurons to mouse astroglia and binding of mouse neurons to chick astroglia were both inhibited by anti-Ng-CAM antibodies. To identify whether the cellular ligands for Ng-CAM differed for neuron-neuron and neuron-glia binding, cells were preincubated with specific antibodies, the antibodies were removed by washing, and Ng-CAM-Covasphere binding was measured. Preincubation of neurons with anti-Ng-CAM antibodies inhibited Ng-CAM-Covasphere binding but similar preincubation of astroglial cells did not inhibit binding. In contrast, preincubation of astroglia with anti-astroglial cell antibodies inhibited binding to these cells but preincubation of neurons with these antibodies had no effect. Together with the data on Covaspheres and liposome aggregation, these findings suggested that Ng-CAM-Covaspheres bound to Ng-CAM on neurons but bound to different molecules on astroglia.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Presumed inhibitory neurons in the macaque inferior temporal cortex: visual response properties and functional interactions with adjacent neurons.

Neurons in area TE of the monkey inferior temporal cortex respond selectively to images of particular objects or their characteristic visual features. The mechanism of generation of the stimulus selectivity, however, is largely unknown. This study addresses the role of inhibitory TE neurons in this process by examining their visual response properties and interactions with adjacent target neurons. We applied cross-correlation analysis to spike trains simultaneously recorded from pairs of adjacent neurons in anesthetized macaques. Neurons whose activity preceded a decrease in activity from their partner were presumed to be inhibitory neurons. Excitatory neurons were also identified as the source neuron of excitatory linkage as evidenced by a sharp peak displaced from the 0-ms bin in cross-correlograms. Most inhibitory neurons responded to a variety of visual stimuli in our stimulus set, which consisted of several dozen geometrical figures and photographs of objects, with a clear stimulus preference. On average, 10% of the stimuli increased firing rates of the inhibitory neurons. Both excitatory and inhibitory neurons exhibited a similar degree of stimulus selectivity. Although inhibitory neurons occasionally shared the most preferred stimuli with their target neurons, overall stimulus preferences were less similar between adjacent neurons with inhibitory linkages than adjacent neurons with common inputs and/or excitatory linkages. These results suggest that inhibitory neurons in area TE are activated selectively and exert stimulus-specific inhibition on adjacent neurons, contributing to shaping of stimulus selectivity of TE neurons.

Action Potentials↗
PubMed1991

[Stereological analysis of GABAergic neurons and calcium binding protein parvalbumin-containing neurons in the rat somatosensory cortex].

The number of neuronal cells in the rat somatosensory cortex (barrel area) has been estimated by a stereological method, disector, using pairs of toluidine-blue stained plastic embedded 0.5 microns thick sections, 3.0 microns distant from each other. Chemical properties of those disector-counted cells were further revealed by applying postembedding immunocytochemical methods on adjacent semithin sections. Thus we analysed quantitatively the number, distribution and proportion of three types of neurons: 1) GABA negative neurons, 2) GABA-like immunoreactive (GABA-LIR) neurons and 3) a specific calcium binding protein parvalbumin (PV) immunoreactive (PV-IR) neurons, which are a subpopulation of GABA-LIR neurons. The densities of total neurons in the rat somatosensory cortex were 55 x 10(3)/mm3. Of neurons 24% and 12% were GABA-LIR and PV-IR, respectively; almost all PV-IR neurons are GABA-LIR and thus about 50% GABA-LIR neurons are PV positive. The number of total neurons under a unit surface area 1mm2 through the thickness of the somatosensory cortex is 85 x 10(3). GABA-LIR neurons were 20 x 10(3) and PV-IR neurons and PV negative GABA-LIR neurons were 10 x 10(3) and 10 x 10(3), respectively. The laminar distribution of each group of neurons shows prominent differences, indicating that the neuronal composition was different from layer to layer. The density of GABA-LIR neuron was highest in layer IV and especially PV-IR neurons were 2-3 times more numerous in layer IV than in layer II/III, V and VI.

Animals↗
PubMed1984

Postnatal development of cat superior colliculus. I. Presumptive neurons, immature neurons and degenerating cells in the intermediate and deep layers.

Presumptive neurons, immature neurons and degenerating structures were found in the intermediate and deep layers of the superior colliculus of normal cats over the age range 7-45 days postnatal. Electron microscopical analysis revealed these structures to be unexpectedly frequent in the early postnatal period. There were 34 immature neurons per 1000 neurons at 7-8 days and 78 per 1000 neurons at 14 days postnatal. Few were found in older cats. Two types of degenerative changes in the neurons were observed: nuclear and cytoplasmic. The number of degenerating structures to be unexpectedly frequent in the early postnatal period. There were 34 immature neurons per 1000 neurons at 7-8 days and 78 per 1000 neurons at 14 days postnatal. Few were found in older cats. Two types of degenerative changes in the neurons were observed: nuclear and cytoplasmic. The number of degenerating neurons was higher at 14 days (28 per 1000 neurons) than at 7-8 days (21 per 1000 neurons), but only a few were found at 30 and 45 days. Degenerative changes were noted in synaptic terminals at all ages studied. The greatest number of degenerating synaptic profiles were observed at 14 and 30 days. They were infrequent in younger or older animals. The number of presumptive neurons does not change significantly over 7-14 days. It is speculated that they persist as a reverse pool of neurons. The increasing number of immature neurons in the period between 7 and 14 days indicates that formation of new cells in the intermediate and deep layers of the superior colliculus continues into the early postnatal period. The degeneration of some neurons and synapses over the same developmental period suggest that the final adjustment of the neuronal composition of the superior colliculus occurs postnatally.

Animals↗
PubMed1996

Structure and function of gustatory neurons in the nucleus of the solitary tract: II. Relationships between neuronal morphology and physiology.

This study employed intracellular recording and labeling techniques to examine potential relationships between the physiology and morphology of brainstem gustatory neurons. When we considered the neuronal response to the four "prototypic" tastants, we were able to demonstrate a positive correlation between breadth of responsiveness and the number of dendritic branch points. An analysis of the response to eight tastants also revealed an association between dendritic spine density and the breadth of responsiveness, with more narrowly tuned neurons exhibiting more spines. Interestingly, a neuron's "best response" was a relatively poor predictor of neuronal morphology. When we focused on those neurons that responded to only one tastant, however, a number of potentially important relationships became apparent. We found that the cells that only responded to quinine were smaller than the neurons that only responded to NaCl, HCl, or sucrose. The HCl-only neurons, however, were more widespread in the rostrocaudal dimension that the neurons that only responded to NaCl. A number of additional structure-function relationships were identified when we examined the neuronal response to selected tastants. We found that neurons that responded to sucrose but not quinine, as well as neurons that responded to quinine but not sucrose, were more widespread in the mediolateral dimension than neurons that responded to both sucrose and quinine. We also discovered that the neurons that responded to NaCl, but not to NH4Cl or KCl, were larger than neurons that responded to all three salts. We believe that these results support the hypothesis that there are relationships between the structure and function of gustatory neurons in the nucleus of the solitary tract, with the data highlighting the importance of three themes: 1) the relationship between dendritic specializations and tuning, 2) the relationship between dendritic arbor orientation and response properties, and 3) the potential importance of stimulus-specific neurons.

Animals↗
PubMed1988

Local circuit neurons of macaque monkey striate cortex: II. Neurons of laminae 5B and 6.

This study investigates the intrinsic organization of axons and dendrites of aspinous, local circuit neurons of the macaque monkey visual striate cortex. These investigations use Golgi Rapid preparations of cortical tissue from monkey aged 3 weeks postnatal to adult. We have earlier (Lund, '87) described local circuit neurons found within laminae 5A and 4C; this present account is of neurons found in the infragranular laminae 5B and 6. Since the majority of such neurons are GABAergic and therefore believed to be inhibitory, their role in laminae 5B and 6, the principal sources of efferent projections to subcortical regions, is of considerable importance. We find laminae 5B and 6 to have in common at least one general class of local circuit neuron-the "basket" neuron. However, a major difference is seen in the axonal projections to the superficial layers made by these and other local circuit neurons in the two laminae; lamina 5B has local circuit neurons with principal rising axon projections to lamina 2/3A, areas whereas lamina 6 has local circuit neurons with principal rising axon projections to divisions of 4C, 4A, and 3B. These local circuit neuron axon projections mimic the different patterns of apical dendritic and recurrent axon projections of pyramidal neurons lying within laminae 5B and 6, which are linked together by both dendritic and axonal arbors of local circuit neurons in their neuropils extending between the two laminae. The border zone between 5B and 6 is a specialized region with its own variety of horizontally oriented local circuit neurons, and it also serves as a special focus for pericellular axon arrays from a particular variety of local circuit neuron lying within lamina 6. These pericellular axon "baskets" surround the somata and initial dendritic segments of the largest pyramidal neurons of layer 6, which are known to project both to cortical area MT (V5) and to the superior colliculus (Fries et al., '85). Many of the local circuit neurons of layer 5B send axon trunks into the white matter, and we therefore, suspect them of providing efferent projections. The axons of lamina 6 local circuit neurons have not been found to make such clear-cut contributions to the white matter.

Animals↗
PubMed1991

Postnatal development of thalamic recipient neurons in the monkey striate cortex: I. Comparison of spine acquisition and dendritic growth of layer 4C alpha and beta spiny stellate neurons.

A quantitative study has been made from Golgi impregnations of the maturation of dendrites and their spines on spiny stellate neurons in the macaque monkey primary visual cortex. The neurons studied lay within either the alpha or the beta division of lamina 4C; previous workers have shown the alpha division neurons to be contacted by thalamic axon terminals arising from the magnocellular division of the lateral geniculate nucleus (LGN) of the thalamus and the beta division neurons to be contacted by parvocellular LGN inputs. Most thalamic terminals and perhaps the majority of other type 1 (Colonnier, '81), presumed excitatory, inputs to these cells make synaptic contacts on the tips of their dendritic spines. Measurement was made of relative changes in the total number of spines on these alpha and beta spiny neurons over age by measuring both spine density along the dendrites and dendritic arbor size in single 90-microns sections from Golgi rapid preparations. Our previous work (Lund et al., '77; Boothe et al., '79) showed a marked proliferation and attrition of spines and dendritic branches to occur in the early postnatal weeks; Rakic et al. ('86) have since proposed that there is a cortexwide synchrony of synapse acquisition and loss during this same period. However, different visual capacities channelled via the magnocellular and parvicellular geniculate relays show different maturational rates (Harwerth et al., '86). This study indicates that the anatomical maturation of spines on the alpha and beta neurons is not temporally coincident from birth to 30 weeks. During this period, phases of spine acquisition and loss on alpha neurons precedes similar phases on beta neurons. The alpha neurons carry a peak spine population at 5-8 weeks postnatal, whereas the beta neurons carry their peak spine populations between 8 and 24 weeks postnatal. At all ages prior to 30 weeks, the two sets of neurons carry quite different total spine populations. Close to 30 weeks of age, the total spine coverage has fallen on both sets of neurons and becomes identical between the alpha and beta neurons. In animals aged 30 weeks to adult, spine coverage per neuron is maintained at a common figure for the alpha and beta neurons despite further growth and disparate dendritic arbor sizes and different local spine densities in the two groups; this suggests that some common sampling paradigm between pre- and postsynaptic elements is adopted by the alpha and beta neurons and also suggests the development of a close functional correlation between the two sets of neurons.

Aging↗
PubMed1986

Functional characterization of preganglionic neurons projecting in the lumbar splanchnic nerves: neurons regulating motility.

Lumbar preganglionic neurons, which projected in the lumbar splanchnic nerves and were probably involved in regulating motility of colon and pelvic organs (motility-regulating, MR neurons), were analyzed for their discharge patterns. The responses of the neurons to the following stimuli were tested: stimulation of arterial baro- and chemoreceptors and of afferents from the urinary bladder, colon, mucosal skin of the anus and perianal hairy skin. The following findings were made: a total of 131 preganglionic neurons were classified as MR neurons; these reacted to natural stimulation of at least one of the afferent inputs from the urinary bladder, colon and anal and perianal skin. The ongoing activity of these neurons did not correlate with the cardiac cycle or the cycle of the artificial ventilation. Most of them did not respond to an increase of blood pressure produced by i.v. injection of adrenaline or noradrenaline; some showed a weak depression or weak excitation which, in the time course, was untypical for visceral vasoconstrictor neurons. Stimulation of arterial chemoreceptors either did not influence MR neurons or produced only a secondary response owing to contraction of the urinary bladder. Ninety-seven preganglionic MR neurons could be subclassified: MR1 neurons were excited by distension and contraction of the urinary bladder and/or inhibited by distension and contraction of the colon (n = 61), a few were excited from both organs (n = 4); MR2 neurons were inhibited by distension and contraction of the urinary bladder and/or excited by distension and contraction of the colon (n = 32). Ninety-five out of 121 MR neurons (78.5%) were excited, 10 (8%) were inhibited and 16 (13%) not influenced by mechanical shearing stimuli applied to the mucosal skin of the anus. Most neurons which were excited by anal stimulation were not influenced by mechanical stimulation of the perianal (perigenital) skin. Twenty-eight per cent of the MR neurons (18 out of 64) were excited or inhibited upon stimulation of perianal skin. A few of these (7 out of 64 neurons, 11%) were involved in reflex responses which were different from those elicited from anal skin. At present no further consistent subclassification of MR1 and MR2 neurons appears possible on the basis of the excitatory and inhibitory anal and perianal reflexes. The results show that the population of visceral preganglionic neurons, which are probably involved in regulation of motility of colon and pelvic organs, is not homogeneous and probably consists of several subpopulations.

Anal Canal↗