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PubMed1988

Neurogenic stimuli alter preoptic area and amygdala unit activity: central effects of olfactory projections on paraventricular nucleus units.

Unit responses were recorded in the preoptic area and amygdala of conscious male rats during exposure to stressful neurogenic stimuli. Olfactory stimulation elicited increases in preoptic area activity on all occasions and also increased activity in the intercalating, medial, and basomedial nuclei of the amygdala, but not in other regions. Acoustic stimulation had less specific effects, even inhibiting unit activity in the central amygdala. A separate series of experiments using urethane-anesthetized rats was carried out to examine the effects of electrical stimulation of the medial amygdala and olfactory tubercle on single-unit activity within the hypothalamic paraventricular nucleus. Inhibition was the predominant response following olfactory tubercle stimulation while excitatory responses predominated following stimulation of the medial amygdala. This was the case particularly for those paraventricular nucleus units identified as projecting to the median eminence (P less than 0.005 vs unidentified cells). The results obtained may be related to the neural regulation of adrenocortical activity as well as higher central nervous activity and have been discussed within these contexts.

Acoustic Stimulation↗
PubMed1982

Phylogeny through brain traits: fifteen characters which adumbrate mammalian genealogy.

Fifteen characters of brain organization are identified for which primitive and derived states can be distinguished, and which are thus useful in reconstructing mammalian phylogeny. The states of the characters are numerically coded in sequence from most primitive to most derived, to facilitate reciprocal comparisons in comprehensive genealogical analyses. The characters include certain features of cerebral circulation, cytoarchitecture, fiber pathways, and sensory projections. Seven characters are shared with nonmammals, a fact which makes then particularly useful for establishing their primitive vs. derived states; the other eight characters are features peculiar to mammals. Ten characters provide impressive reinforcement for traditional major grouping of the species, while five provide bases for new ideas about mammalian relationships.

Animals↗
PubMed2000

Disruption of the olfactoretinal centrifugal pathway may relate to the visual system defect in night blindness b mutant zebrafish.

We describe here a dominant mutation, night blindness b (nbb), which causes an age-related visual system defect in zebrafish. At 4-5 months of age, dark-adapted nbb(+/-) mutants show abnormal visual threshold fluctuations when measured behaviorally. Light sensitizes the animals; thus early dark adaptation of nbb(+/-) fish is normal. After 2 hr of dark adaptation, however, visual thresholds of nbb(+/-) mutants are raised on average 2-3 log units, and rod system function is not detectable. Electroretinograms recorded from nbb(+/-) mutants are normal, but ganglion cell thresholds are raised in prolonged darkness, suggesting an inner retinal defect. The visual defect of nbb(+/-) mutants may be likely caused by an abnormal olfactoretinal centrifugal innervation; in nbb(+/-) mutants, the olfactoretinal centrifugal projection to the retina is disrupted, and the number of retinal dopaminergic interplexiform cells is reduced. A similar visual defect as shown by nbb(+/-) mutants is observed in zebrafish in which the olfactory epithelium and olfactory bulb have been excised. Homozygous nbb fish display an early onset neural degeneration throughout the CNS and die by 7-8 d of age.

Age Factors↗
PubMed2001

The insular but not the perirhinal cortex is involved in the expression of fully-kindled amygdaloid seizures in rats.

We have previously reported an important excitatory role of the perirhinal cortex (PRC) in rat kindling development using an immunohistochemistry technique. In this study, we investigated the roles of the PRC and the insular cortex (INS) located rostral to the PRC, in fully-kindled amygdaloid seizures, using a microinjection technique in the rat kindling model of epilepsy. Following the establishment of daily kindling, we investigated the effects of microinjections of procaine hydrochloride, 2-amino-5-phosphonovalerate (APV; an N-methyl-D-aspartate (NMDA) receptor antagonist) and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)-quinoxaline (NBQX; an alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) receptor antagonist). Microinjections of these drugs into the ipsilateral PRC did not suppress kindled seizures. The possibility is that the process of kindling development forms novel seizure-generalization pathways that do not require further activation of the PRC. On the other hand, procaine and APV injected into the ipsilateral INS significantly suppressed kindled seizures. The manner of suppression appeared to be 'all or none'. It is therefore possible that at least the activation of NMDA receptors in the INS is necessary to express generalized kindled amygdaloid seizures.

Amygdala↗
PubMed1994

Vomeronasal system, LHRH, and sex behaviour.

Vomeronasal chemosensory input is important for male hamster mating behavior, especially in inexperienced animals. Experiments reviewed here showed that intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) substantially restores mating behavior impaired by removal of vomeronasal organs in inexperienced hamsters. An analogue molecule Ac5-10LHRH, which fails to release luteinizing hormone (LH) from the pituitary, has similar behavioural effects. These findings are consistent with the idea that vomeronasal sensory input may trigger intracerebral release of LHRH which then facilitates mating behaviour. Immunocytochemistry for the immediate-early gene-product Fos, used as an indicator of regional brain activation, indicates a selective activation of central vomeronasal pathways during mating behaviour. Chemosensory and other sensory inputs contribute to activation in medial amygdala and bed-nucleus of stria terminalis, but medial preoptic/anterior hypothalamic area activation appears more closely tied to mating behavior itself. Any of these areas may be sites of interaction between vomeronasal chemosensory input and LHRH-containing cells and fibers.

Amygdala↗
PubMed1987

Frequency potentiation of a central cholinergic circuit.

We have used the cholinergic projection from the nucleus of the horizontal limb of the diagonal band (HDB) to the olfactory bulb as a model for studying the neurophysiology of cholinergic projections from the basal forebrain to cortical structures. Although single shocks to HDB have little effect upon function of the target structure, short periods of repetitive stimulation produce profound changes. These observations are discussed in terms of the known physiology of central cholinergic systems and the significance of cholinergic synaptic potentiation for Alzheimer's disease.

Animals↗
PubMed1999

Inhibitory and excitatory responses of olfactory receptor neurons of xenopus laevis tadpoles to stimulation with amino acids

Recordings were made from olfactory receptor neurons of Xenopus laevis tadpoles using the patch-clamp technique to investigate the responses of these cells to odorants. Four amino acids (glutamate, methionine, arginine and alanine) both individually and as a mixture were used as stimuli. Of the 156 olfactory neurons tested, 43 showed a response to at least one of the stimuli. Of the cells tested, 19 % responded to glutamate, 16 % to methionine, 12 % to arginine and 10 % to alanine. Each amino acid was able to induce both excitatory and inhibitory responses, although these occurred in different cells. Each amino acid produced approximately equal numbers of inhibitory and excitatory responses. Inhibitory responses could best be observed in the perforated-patch configuration using gramicidin as an ionophore and a recording configuration that is a current-clamp for fast signals and a voltage-clamp for slow signals. The diversity of the odorant responses, in particular the existence of excitatory and inhibitory responses, is not consistent with a single transduction pathway in olfactory neurons of Xenopus laevis tadpoles.

Journal Article↗
PubMed1988

Spatial and temporal patterns of oligodendrocyte differentiation in rat cerebrum and cerebellum.

Oligodendrocytes are largely generated postnatally during mammalian CNS development. We have used a variety of antibodies to label immature neuroectodermal cells and developing oligodendrocytes in several areas of the rat CNS. Antibodies included those to GD3 ganglioside, a characteristic glycolipid of immature cells; carbonic anhydrase (CA), contained primarily in oligodendrocytes; and galactocerebroside and myelin basic protein, myelin components. Several aspects of oligodendrocyte development were examined: changes in shapes of immature cells with respect to time and to location within the brain, the sequential acquisition of the various markers, and possible sites of origin and pathways of precursor cell migration. Our observations suggest that oligodendrocytes in the forebrain and cerebellum arise from cells of the subventricular zone (SVZ) adjacent to the ventricles and migrate into and through nearby white and gray matter. During maturation, there are distinct patterns of morphological changes that correlate with time, locations of the cells in the brain, and acquisition of specific markers.

Animals↗
PubMed1999

Establishment of the FMRFamide-immunoreactive olfacto-retinalis pathway during ontogeny of the rainbow trout (Oncorhynchus mykiss).

Migration of neurons is one of the mechanisms establishing normal central nervous system connectivity during ontogeny. Proper timing of axonal sprouting is relevant in the same context. In the present study, we used the immunoreactivity of the tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2) to visualize the olfacto-retinalis projection during trout ontogeny. It starts to innervate the retina two to four weeks after hatching, in contrast to reports on salmon where it only appears after the fish are imprinted on their natal stream.

Aging↗
PubMed1986

Cholinergic and GABAergic afferents to the olfactory bulb in the rat with special emphasis on the projection neurons in the nucleus of the horizontal limb of the diagonal band.

We have examined the location of cholinergic and GABAergic neurons that project to the rat main olfactory bulb by combining choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) immunohistochemistry with retrograde fluorescent tracing. Since many of the projection neurons are located in subcortical basal forebrain structures, where the delineation of individual regions is difficult, particular care was taken to localize projection neurons with respect to such landmarks as the ventral pallidum (identified on the basis of GAD immunoreactivity), the diagonal band, and medial forebrain bundle. In addition, sections with fluorescent tracers or immunofluorescence were counterstained for Nissl substance in order to correlate tracer or immunopositive neurons with the cytoarchitecture of the basal forebrain. The majority of the cholinergic bulbopetal neurons are located in the medial half of the nucleus of the horizontal limb of the diagonal band (HDB), whereas only a few are located in its lateral half. A substantial number of cholinergic bulbopetal cells are also found in the sublenticular substantia innominata. A small number of cholinergic bulbopetal neurons, finally, are located in the ventrolateral portion of the nucleus of the vertical limb of the diagonal band. At the level of the crossing of the anterior commissure, approximately 17% of the bulbopetal neurons in the HDB are ChAT-positive. The noncholinergic bulbopetal cells are located mainly in the lateral half of the HDB. GAD-containing bulbopetal neurons are primarily located in the caudal part of the HDB, especially in its lateral part. About 30% of the bulbopetal projection neurons in the HDB are GAD-positive. A few GAD-positive bulbopetal cells, furthermore, are located in the ventral pallidum, anterior amygdaloid area, deep olfactory cortex, nucleus of the lateral olfactory tract, lateral hypothalamic area, and tuberomamillary nucleus. The topography of bulbopetal neurons was compared to other projection neurons in the HDB. After multiple injections of fluorescent tracer in the neocortex, retrogradely labeled neurons were concentrated in the most medial part of the HDB, while neurons projecting to the olfactory and entorhinal cortices were located in the ventral part of the HDB. These results show that the cells of the HDB can be divided into subpopulations based upon projection target as well as transmitter content. Furthermore, these subpopulations correspond, at least to a considerable extent, to areas that can be defined on cyto- and fibroarchitectural grounds.

Animals↗
PubMed1988

Plasticity of intra-amygdaloid connections following the denervation of fibers from accessory olfactory bulb to medial amygdaloid nucleus in adult rat: immunohistochemical study of anterogradely transported lectin (Phaseolus vulgaris leucoagglutinin).

The rearrangement of the terminations of intra-amygdaloid fibers was examined in the medial amygdaloid nucleus (MAN) following denervation of the fibers from the accessory olfactory bulb (AOB) of adult rat using immunohistochemistry of anterogradely transported lectin (Phaseolus vulgaris leucoagglutinin, PHA-L). The AOB was removed unilaterally by suction at two months before the PHA-L injection. The PHA-L was injected bilaterally into the posteromedial region of the amygdala (posteromedial amygdaloid nucleus and amygdala-hippocampal transitional area). After the tissue was processed by the routine immunohistochemical method, the immunologically labeled axons and axon terminals in the MAN were observed with the light microscope. On the control side, labeled axons were observed in the cellular part of the MAN, but they were not found in the molecular layer in which the fibers from the accessory olfactory bulb terminate. On the side of the AOB removal, the labeled axons were found not only in the cellular part but also in the molecular layer. Electron microscopic observations showed that the labeled axon terminals made synaptic contacts in the molecular layer. These results indicate that terminals of intra-amygdaloid fibers expand from the cellular part to the molecular layer in the MAN and make synaptic contacts in this layer following the denervation of the AOB fibers.

Amygdala↗
PubMed2004

Olfactory receptor neuron axon targeting: intrinsic transcriptional control and hierarchical interactions.

From insects to mammals, olfactory receptor neurons (ORNs) expressing a common olfactory receptor target their axons to specific glomeruli with high precision. Here we show in Drosophila that the POU transcription factor Acj6 controls the axon targeting specificity of a subset of ORN classes, as defined by the olfactory receptors that they express. Of these classes, some require Acj6 cell-autonomously, whereas others require Acj6 cell-nonautonomously. Mosaic analyses show that cooperative targeting occurs between axon terminals of the same ORN classes and that there are hierarchical interactions among different ORN classes. We propose that the precision of ORN axon targeting derives from both intrinsic transcriptional control and extensive axon-axon interactions.

Animals↗
PubMed1999

Dendritic pattern development of the honeybee antennal lobe neurons: a laser scanning confocal microscopic study.

The processing of odorant signals is performed, in the olfactory bulb of vertebrates or in the antennal lobe of insects, by different types of neurons which display specific morphological and functional features. The present work characterizes the morphogenesis of the main neuronal types which participate in olfactory discrimination in the adult honeybee (Apis mellifera). Neurons were stained intracellularly with Lucifer yellow at different stages of pupal development and in the adult, and imaged by laser scanning confocal microscopy. Attending to branching patterns, all pupal neurons could be attributed to morphological types previously established in the adult. Given the functional importance of intraglomerular dendritic arbors in the processing of olfactory information, the study focused on their development. The two main classes, dense and sparse intraglomerular arbors, display adultlike features as early as the second day of pupal development. However, morphometric measurements and confocal observations show that their general pattern undergoes continuous maturation processes until late pupal stages and after emergence of the adult. Among these, the results point out a pruning of dendritic branches in sparse arbors, but not in dense arbors.

Age Factors↗
PubMed2005

The "olfactostriatum" of snakes: a basal ganglia vomeronasal structure in tetrapods.

The olfactostriatum is a portion of the basal ganglia of snakes situated ventromedially to the nucleus accumbens proper. It receives a major vomeronasal input from the nucleus sphericus, the primary target of accessory olfactory bulb efferents. Recently, the ophidian olfactostriatum has been characterized on the basis of chemoarchitecture (distribution of serotonin, neuropeptide Y and tyrosine hydroxylase) and hodology (afferent and efferent connections). In contrast to the nucleus accumbens proper, the olfactostriatum is densely immunoreactive for serotonin and neuropeptide Y and sparsely immunoreactive for tyrosine hydroxylase. The nucleus accumbens proper and the olfactostriatum share most afferent connections except those originating in the nucleus sphericus, which are exclusively directed to the olfactostriatum. Similarly, the nucleus accumbens proper and the olfactostriatum show a similar pattern of efferent connections including those going to the ventral pallidum, although the olfactostriatum alone projects to the main and accessory olfactory bulbs as well as some amygdaloid nuclei. On the basis of its chemoarchitecture, the olfactostriatum resembles the mammalian ventral pallidum (but also the shell of the nucleus accumbens). Its connections, however, suggests that the olfactostriatum could be a specialized portion of the shell of nucleus accumbens extended more ventromedially than previously believed and devoted to processing vomeronasal information. Comparative data suggest that a similar structure is present in the basal ganglia of amphibians and mammals.

Animals↗
PubMed2001

Differing, spatially restricted roles of ionotropic glutamate receptors in regulating the migration of gnrh neurons during embryogenesis.

We have examined here the role of glutamate in regulating the process of tangential neuronal migration during embryogenesis by investigating the roles of AMPA and NMDA receptors in the migration of the gonadotropin-releasing hormone (GnRH) neurons from the nose to the hypothalamus. We first determined that GluR1-4 subunit mRNAs were present from embryonic day (E) 12.5 along the complete nose-brain migratory pathway of the GnRH neurons, whereas that of the obligatory NMDAR1 transcript was present only in brain regions of GnRH migration. In vivo studies revealed that AMPA receptor antagonism between E12.5 and E16.5 resulted in a significant (p < 0.05) accumulation of GnRH neurons in the nose adjacent to the cribiform plate. In contrast, NMDA receptor antagonism over E12.5-E16.5 or E13.5-E16.5 caused a selective increase (p < 0.05) in the number of GnRH neurons located in their final resting place within the diagonal band of Broca and preoptic area. Dual-labeling studies using GnRH promoter-LacZ transgenic mice, which facilitate the identification of receptors in GnRH neurons, identified the presence of NMDAR1 receptors in approximately 6% of embryonic GnRH neurons located throughout the migratory pathway. Postnatally, the percentage of GnRH neurons expressing NMDAR1 increased to 50%. These results indicate that tonic AMPA receptor activation enhances the migration of GnRH neurons from the nose into the brain, whereas that of NMDA receptor activation slows the final phase of GnRH migration within the forebrain. These in vivo observations demonstrate differing, spatially restricted roles for AMPA and NMDA receptor activation in the process of tangential neuronal migration.

Animals↗
PubMed1985

Effects of lesions in the amygdala and periventricular hypothalamus on striatal somatostatin-like immunoreactivity.

Somatostatin has been found in substantial amounts in the basal ganglia by radioimmunoassay and has been demonstrated in both neurons and nerve terminals. Since the levels of somatostatin have been shown to vary in Huntington's and Alzheimer's disease it was of interest to see whether such changes could be produced experimentally. Lesions of the periventricular nucleus of the hypothalamus and knife cuts adjacent to this nucleus had no effect on striatal somatostatin-like immunoreactivity (SLI). Similarly lesions of medio-dorsal frontal cortex, and those isolating pyriform cortex or the olfactory bulb had no effect on striatal SLI. Removal of the amygdala resulted in significant increases in SLI in the ipsilateral striatum and nucleus accumbens, suggesting loss of an inhibitory interaction. Stria terminalis lesions failed to reproduce this effect suggesting that it is mediated via amygdalo-striatal projections traveling in the dorsal longitudinal bundle. Other findings support a somatostatin projection to the amygdala from the bed nucleus of the stria terminalis and one from the amygdala to the ventromedial hypothalamus.

Amygdala↗
PubMed1984

Firing properties of cat basal forebrain neurones during sleep-wakefulness cycle.

Neuronal activity was studied in the basal forebrain area (BFA) of freely moving cats during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS). Two classically synchronizing and hypnogenic regions, the preoptic area (POA) and the olfactory tubercle (OT) were explored by microelectrodes. Compared to W, the discharge rate in most of the POA cells was not modified or was slightly reduced by SWS, but it was increased by PS. Half of the OT cells increased slightly their firing frequency during falling asleep. A great proportion of OT neurones showed facilitation of activity during PS also, which in half of the cells started already in the last seconds of SWS. The results are discussed from the point of view of the synchronizing and hypnogenic influence attributed to POA and OT.

Animals↗
PubMed1994

The development of serotonergic projections to the olfactory bulb of Monodelphis domestica (the grey, short-tailed opossum).

The offspring of Monodelphis domestica (grey, short-tailed opossum) are born in a very immature state after a short (14-day) gestation period. As a result, they provide a useful mammalian model for examining quite early stages of brain maturation. The present study demonstrates that the onset and development of serotonergic (5-HT) projections to the Monodelphis olfactory bulb can be traced entirely after birth. 5-HT was visualized in tissue sections from postnatal day 5 (P5), P10, P20, P30, and adult opossums using avidin-biotin peroxidase immunocytochemistry. 5-HT afferent fibers are rare in the bulb until P10. Maturation occurs slowly, but by P30, 5-HT fibers assume the adult form characterized by preferential glomerular innervation. Due to the postnatal development, slow maturation, and specificity of innervation patterns, the Monodelphis bulb provides a model with which to study the regulation of serotonergic development.

Aging↗