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PubMed1991

Age-related remodeling of glutamic-acid decarboxylase-labeled elements in deafferented piriform cortex of rats.

Olfactory bulb (OB) removal has been shown to result in plasticity in the piriform cortex (PC) that is age dependent. We are studying this phenomenon using immunoelectron microscopy of glutamic acid decarboxylase immunoreactivity (GAD, the enzymatic precursor for GABA) at selected postnatal ages and in adults with emphasis on short survival times of 4-7 days after OB ablation. Normally GAD-labeled synaptic terminals form type II symmetric contacts onto unlabeled dendrites and GAD-labeled dendrites receive type I, asymmetric contacts from unlabeled terminals (Westenbroek, et al., 1988a). The OB lesion results in degenerating terminals with type I contacts onto unlabeled and onto GAD-labeled dendrites. Type I postsynaptic sites may be seen partially contacted by or entirely devoid of degenerating terminals and occasionally may be apposed to variable degrees by normal unlabeled or by GAD-positive terminals. Subsequently, some GAD-labeled terminals may form asymmetric type I contacts usually with unlabeled dendrites and rarely with GAD-labeled dendrites. The findings are most common in the youngest subjects and essentially absent in the adult subjects. A sequence of reinnervation of deafferented type I sites by GAD-labeled terminals is suggested for the formation of this "atypical" synapse and the sequelae of this reorganization are discussed.

Aging↗
PubMed2004

Convergence of olfactory and gustatory connections onto the endopiriform nucleus in the rat.

Electrical and optical recordings were made from slice preparations including the piriform and gustatory cortices. Electrical stimulation of the gustatory cortex evoked a characteristic field potential in the endopiriform nucleus. A field potential was induced in the endopiriform nucleus by stimulation of the piriform cortex. Voltage-sensitive dye studies showed that stimulation of the piriform cortex induced signal propagation from the piriform cortex to endopiriform nucleus, whereas stimulation of the gustatory cortex did the same from the gustatory cortex to endopiriform nucleus via the agranular division of the insular cortex. After stimulation of the endopiriform nucleus, optical signals propagated not only to the piriform cortex but also to the gustatory cortex via the agranular division of the insular cortex. The olfactory and gustatory pathways appeared to be reciprocally connected. Unit recordings indicated that olfactory and gustatory activity converged onto a single neuron of the endopiriform nucleus. It is suggested that the cortical integration of olfactory and gustatory information could modulate mechanisms involved in food selection and emotional reactions relating to the chemical senses.

Animals↗
PubMed1990

Transection of the rat olfactory nerve increases glial fibrillary acidic protein immunoreactivity from the olfactory bulb to the piriform cortex.

Astrocytic glial fibrillary acidic protein (GFAP) immunoreactivity in response to retrograde changes of motoneurons after axotomy has been the subject of a number of reports. In contrast, this study examined the astrocytic GFAP immunoreactivity in response to axotomy in a sensory system, the adult rat olfactory system. The purpose of this study was to determine, by immunolabeling GFAP, the extent and transience of astrocytic reactivity in the olfactory system. Unilateral transection of the olfactory nerve fascicles was performed intracranially at the level of the cribriform plate. Rats were allowed to survive from 24 hours to 1 month after axotomy. GFAP immunolabeling was examined throughout the rat olfactory system using the peroxidase-anti-peroxidase method. After axotomy, a transient increase occurred in the astrocytic GFAP immunoreactivity in the ipsilateral olfactory system. The greatest enhancement of GFAP immunoreactivity in the olfactory system occurred at 48 hours post-axotomy. Increased GFAP immunoreactivity occurred not only along the axons and synaptic endings of the injured primary olfactory neurons, but also along the dendrites, cell bodies, axons, and synaptic endings of the secondary sensory neurons. The increased GFAP immunoreactivity was specifically associated with the anatomical distribution pathways of the primary and secondary olfactory neurons. Increased GFAP immunoreactivity was not altered until 14 days post-axotomy. At 1 month post-axotomy, GFAP immunoreactivity returned to control levels. The time course and transience of increased GFAP immunoreactivity closely correlates with the time course of rat primary olfactory neuronal degeneration and regeneration after axotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Polysynaptic olfactory pathway to the ipsi- and contralateral entorhinal cortex mediated via the hippocampus.

Interactions between olfactory cortices and the hippocampus support sensory discrimination and spatial learning functions. The olfactory input accesses the hippocampal formation via a polysynaptic pathway mediated by the lateral and rostral entorhinal cortex (EC). We recently demonstrated that following repetitive stimulation of the lateral olfactory tract (LOT) at 2-8 Hz, a delayed response (onset at circa 60 ms) was evoked in the caudal portion of the EC, identified as medial EC, that does not receive a direct olfactory input. By performing simultaneous laminar profile analysis in the EC and in different hippocampal subfields, we conclusively demonstrate that the delayed EC response evoked by repetitive ipsilateral LOT stimulation is headed by the sequential activation of the dentate gyrus and the CA3/CA1 subfields in the septal and temporal hippocampus. Repetitive stimulation of the contralateral LOT also induced an EC response that peaked at 76.28+/-2.42 ms (n=15). Current source density analysis and time-delay analysis of simultaneous field potential laminar profiles performed from the EC and from DG, CA3 and CA1 hippocampal subfields suggested that the contralateral EC response is mainly carried by an intrahippocampal CA3-CA3 commissural pathway. Contralateral LOT stimulation also induced a later EC component (delay >100 ms) generated in the superficial layers, mediated either by local associative interactions or by extrahippocampal circuits. The opportunity to activate the ipsi- and contralateral olfactory pathways in the same experiment and to record field potentials profiles simultaneously in different structures of both hemispheres in the isolated guinea-pig brain confirms that this preparation is unique and is particularly suitable for investigating the system physiology of the limbic region. The present study demonstrates that patterned stimulation of the olfactory input that mimics sniffing patterns during odor discrimination induces a diffuse activation of both ipsi- and contralateral hippocampi and ECs. The findings contribute to the understanding the physiological mechanisms that underlie associative interactions between olfactory and non-olfactory cortical inputs converging into the mesial temporal region.

Animals↗
PubMed2000

Cellular localization of serotonin(2A) (5HT(2A)) receptors in the rat brain.

The serotonin(2A) (5HT(2A)) receptors have been shown to play an important role in several psychiatric disorders, including depression, schizophrenia, and alcoholism. This immunohistochemical study examined the cellular localization of 5HT(2A) receptors in various rat brain structures (olfactory, striatum, cortex, hippocampus, and amygdala). The colocalization of 5HT(2A) receptors in astrocytes was performed by double-immunofluorescence staining of 5HT(2A) receptors and of glial fibrillary acidic protein (GFAP) using confocal laser microscopy. 5HT(2A) receptor immunolabeling was observed in olfactory bulbs, neostriatum, hippocampus, amygdala, and neocortex. Somata and dendrites of pyramidal cells in the frontal cortex (layer V) were densely labeled with 5HT(2A) receptors. In several other brain structures (hippocampus, amygdala, striatum, olfactory structures), 5HT(2A) receptor immunolabeling was found in cell bodies and processes of neurons. 5HT(2A) receptor immunolabeling was also observed in GFAP-positive cells of the various brain structures we investigated (layers I/VI of the neocortex, corpus callosum, hippocampal fissure and hilus, and amygdala). These results indicate that 5HT(2A) receptors are expressed in neurons and astrocytes and suggest the possibility that not only neuronal but also glial 5HT(2A) receptors have functional implications in psychiatric disorders.

Amygdala↗
PubMed1992

Nerve growth factor increases calcium binding protein (calbindin-D28K) in rat olfactory bulb.

Calbindin-D28K (CaBP28K) is a soluble intracellular protein capable of sequestering micromolar concentrations of calcium. The in vivo regulation of CaBP28K by recombinant human nerve growth factor (rhNGF) was studied in adult, male rats. Via Alzet 2002 pumps, each rat received, for 14 days, a lateral ventricle infusion (i.c.v.; n = 5-6/group) of 12 microliters PBS/day containing 1.0 microgram cytochrome C (control) or an equal amount of rhNGF. Six other animals received a vehicle or rhNGF infusion into the central neostriatum. CaBP28K was elevated by 75% (P less than 0.01) in the olfactory bulb following i.c.v. rhNGF in each of two experiments and was not altered in the temporal cortex, hippocampus, olfactory tubercle, cerebellum, or neostriatum. Direct striatal injections of rhNGF did not alter CaBP28K in the neostriatum or other regions (including the olfactory bulb). The increases in olfactory bulb CaBP28K protein levels were verified via Western blot analysis. CaBP28K immunocytochemistry revealed that 33% of olfactory bulb neurons are immunoreactive for CaBP28K and that the number or proportion of immunoreactive neurons did not change with i.c.v. infusions of rhNGF, suggesting that exogenously delivered rhNGF augments the content of CaBP28K in olfactory bulb neurons that normally express the protein. Endogenous NGF may function as a neuroprotective factor by enhancing the ability of these cells to sequester cytoplasmic calcium and retard calcium-mediated neurodegeneration.

Animals↗
PubMed1990

Ontogeny of atrial natriuretic factor (ANF) binding in various areas of the rat brain.

In order to evaluate the possibility that ANF might be associated with brain maturation, we have studied the distribution of ANF binding sites as a function of brain development in the rat. Using in vitro autoradiography, we have observed that ANF binding first appeared before the 13th day of foetal life. In some brain structures, the changes in ANF binding concentration and distribution were dramatic during maturation. In 13-day old foetus, specific ANF binding was observed in cerebral cortex and olfactory bulb. On the 17th day of foetal life, two labeled layers were observed in the cerebral cortex: the basal layer (cortical plate) and the superficial layer. With further development, the ANF binding of the cortical plate decreased whereas the labeling increased in the superficial layer so that 9 days after birth a strong labeling was observed in the superficial layer of the cortex. Thereafter the density of ANF binding rapidly diminished and almost no specific labeling could be detected in the cortex of adult animals. In the hippocampus and amygdaloid complex, ANF binding was first detected at birth and increased rapidly in the following days to reach maximal concentration 5 days after birth. Then, the binding gradually decreased with age and completely disappeared in adult animals. In some other structures, such as the habenula, cerebellum, thalamus and some hypothalamic nuclei, the specific ANF binding appeared around the time of birth, increased until adulthood was reached, and then remained stable. These results indicate that ANF binding sites are transiently associated with some brain structures during maturation and suggest that ANF might be involved in brain development.

Aging↗
PubMed2000

Autoradiographic analysis of N-methyl-D-aspartate receptor binding in monkey brain: effects of 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine and levodopa treatment.

The anatomic distribution of N-methyl-D-aspartate receptors was investigated in the squirrel monkey brain using quantitative autoradiography with [125I]MK-801 as the radioligand. A heterogeneous distribution of [125I]MK-801 binding sites was observed, with the most intense expression in the outer cortex, hippocampus, olfactory tubercle, caudate and putamen. High levels were also observed in the thalamus, nucleus accumbens and inner cortex, with moderate levels in the claustrum. Relatively low expression levels were detected in the subthalamic nucleus with no apparent binding in the globus pallidus and the substantia nigra. Characterization of striatal [125I]MK-801 binding yielded a B(max) of 63.5 fmol/mg tissue and K(d) of 0.53 nM in the caudate, with similar values for the putamen. Experiments were subsequently performed to compare striatal [125I]MK-801 binding in the following four experimental groups: (i) control animals injected with saline; (ii) monkeys treated with levodopa; (iii) animals rendered parkinsonian after exposure to the neurotoxicant 1-methyl-4-phenyl-1, 2,3,6-tetrahydropyridine; and (iv) dyskinetic monkeys treated with both 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and levodopa. No changes were observed in 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine-lesioned animals compared with the saline control group. However, administration of levodopa to either unlesioned or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys resulted in a significant decrease in [125I]MK-801 binding in both the caudate and putamen. The data indicate that levodopa exerts a modulatory effect on the striatal glutamatergic system and suggest that a down-regulation of N-methyl-D-aspartate receptors by levodopa, combined with a deficiency in nigrostriatal dopamine function, may play a role in the development of levodopa induced dyskinesias.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2004

Adult bone marrow stromal cells in the embryonic brain: engraftment, migration, differentiation, and long-term survival.

We recently differentiated adult rat and human bone marrow stromal cells (MSCs) into presumptive neurons in cell culture. To determine whether the MSCs assume neuronal functions in vivo, we now characterize for the first time engraftment, migration, phenotypic expression, and long-term survival after infusion into embryonic day 15.5 (E15.5) rat ventricles in utero. By E17.5, donor cells formed discrete spheres in periventricular germinal zones, suggesting preferential sites of engraftment. The cells expressed progenitor vimentin and nestin but not mature neuronal markers. By E19.5, a subset assumed elongated migratory morphologies apposed to radial nestin-positive fibers running through the cortical white matter and plate, suggesting migration along radial glial processes. Cells remaining in germinal zones extended long, vimentin-positive fibers into the parenchyma, suggesting that the MSCs generated both migratory neurons and guiding radial glia. Consistent with this suggestion, >50% of cultured mouse MSCs expressed the neuroprecursor/radial glial protein RC2. From E19.5 to postnatal day 3, MSCs populated distant areas, including the neocortices, hippocampi, rostral migratory stream, and olfactory bulbs. Whereas donor cells confined to the subventricular zone continued to express nestin, cells in the neocortex and midbrain expressed mature neuronal markers. The donor cells survived for at least 2 months postnatally, the longest time examined. Confocal analysis revealed survival of thousands of cells per cubic millimeter in the frontal cortex and olfactory bulb at 1 month. In the cortex and bulb, 98.6 and 77.3% were NeuN (neuronal-specific nuclear protein) positive, respectively. Our observations suggest that transplanted adult MSCs differentiate in a regionally and temporally specific manner.

Animals↗
PubMedDate not supplied

[Comparative reactivity of the neo-, paleo- and archicortex of the brain under conditions of ether and hexanal anesthesia].

In acute experiments on dogs subject to investigation under ether- and hexobarbital sodium-induced anesthesia was comparative reactivity of the neo-(sensomotor region), paleo-(hippocampus) and archicortex (olfactory lobe) of the brain. It was found that following administration of low and medium doses of general anesthetics more marked EEG changes, with but an insignificant inhibition of respirations and a slight fall in arterial pressure, were observed to occur in the hippocampus and in the olfactory lobe, as against the biocurrents in the sensomotor region. Such a regularity continued for as long as the oxygen tension in the neocortex was maintained at a level higher than in the paleo-and archicortex. Upon introduction of toxic ether and hexobarbital doses the oxygen tension in the neocortex dropped earlier and the inhibition of its bioelectric activity would set in concurrently or sooner than in the olfactory lobe and in the hippocampus.

Animals↗
PubMed1996

Synthesis and in vivo studies of a selective ligand for the dopamine transporter: 3 beta-(4-[125I]iodophenyl) tropan-2 beta-carboxylic acid isopropyl ester ([125I]RTI-121).

A selective ligand for the dopamine transporter 3 beta-(4-iodophenyl)tropan-2 beta-carboxylic acid isopropyl ester (RTI-121) has been labeled with iodine-125 by electrophilic radioiododestannylation. The [125I]RTI-121 was obtained in good yield (86 +/- 7%, n = 3) with high radiochemical purity (> 99%) and specific radioactivity (1210-1950 mCi/mumol). After i.v. administration of [125I]RTI-121 to mice, the rank order of regional brain tissue radioactivity (striatum > olfactory tubercles > > cortex, hippocampus, thalamus, hypothalamus, cerebellum) was consistent with dopamine transporter labeling. Specific in vivo binding in striatum and olfactory tubercles was saturable, and was blocked by the dopamine transporter ligands GBR 12,909 and (+/-)-nomifensine. By contrast, binding was not reduced by paroxetine, a serotonin transporter inhibitor, or desipramine, a norepinephrine transporter inhibitor. A variety of additional drugs having high affinities for recognition sites other than the neuronal dopamine transporter also had no effect. The [125I]RTI-121 binding in striatum and olfactory tubercles was inhibited by d-amphetamine in dose-dependent fashion. Nonmetabolized radioligand represents 85% of the signal observed in extracts of whole mouse brain. Thus, [125I]RTI-121 is readily prepared, and is a useful tracer for dopamine transporter studies in vivo.

Amphetamine↗
PubMed1986

Development and regional expression of beta nerve growth factor messenger RNA and protein in the rat central nervous system.

The presence of nerve growth factor (NGF) mRNA and protein in the rat central nervous system is documented. Blot-hybridization analysis showed an abundance of NGF mRNA in the hippocampus, cerebral cortex, and olfactory bulb. Enzyme immunoassay confirmed significant levels of a NGF-like protein in the hippocampus and cerebral cortex. Bioassay of a NGF-like immunoaffinity-purified protein from these regions was physiologically indistinguishable from NGF. Immunohistochemistry revealed a widespread distribution of NGF-like reactivity in the adult brain, preferentially in fiber tracts. NGF mRNA accumulation began at birth, with adult levels reached 3 weeks postnatally. Enzyme immunoassay detected the presence of a NGF-like protein in the embryonic rat brain. Postnatally, the level of NGF-like protein reached a maximum at 3 weeks. Additionally, a distinct fetal form of NGF may exist.

Animals↗
PubMed2000

Local and cortical effects of olfactory bulb lesions on trophic support and cholinergic function and their modulation by estrogen.

This study determined whether olfactory bulb lesions would affect trophic support to its afferent, the horizontal limb of the diagonal band of Broca (hIDBB), and if estrogen would ameliorate the effects of neural injury in this circuit. NMDA injections into the olfactory bulb resulted in neural injury as indicated by cell loss and increased glial fibrillary acidic protein immunoreactivity. Olfactory bulb lesions severely reduced BDNF expression in its afferent, the hIDBB, while NGF was only reduced in lesioned animals deprived of estrogen. In the olfactory bulb itself, lesions increased BDNF expression, but not NGF. Paradoxically, bulb lesions up-regulated both NGF and BDNF in another target of the hIDBB, the cingulate cortex. Moreover, olfactory bulb lesions affected choline uptake and ChAT activity locally, as well as in the cingulate cortex. Estrogen significantly attenuated the lesion-induced loss of choline uptake in the cingulate cortex, but not at the primary lesion site. Collectively, these results indicate that neural injury to one limb of the forebrain cholinergic system may result in collateral damage to other limbs of this system, suggesting a mechanism for the progression of neurodegenerative diseases, such as Alzheimer's disease, that involve the cholinergic system. Furthermore, these data also indicate that estrogen selectively attenuates certain lesion-induced deficits.

Acetylcholine↗
PubMed1986

Regional alterations in serotonin metabolism induced by oral exposure of rats to polychlorinated biphenyls.

Adult male rats were gavaged with a mixture of Aroclors 1254 and 1260 at a dose level of either 500 or 1000 mg/kg and were killed on post-gavage days 1, 3, 7 and 14. Total PCB concentrations and concentrations of serotonin and its major central metabolite, 5-hydroxyindoleacetic acid, were determined in the dorsal frontal cortex, lateral olfactory tract, hippocampus, medial-basal hypothalamus and brainstem. Differences in the initial concentrations and redistribution patterns of PCBs were observed in the brain regions examined. Serotonin concentrations were reduced in frontal cortex and hippocampus, unaffected in hypothalamus and brainstem and elevated in lateral olfactory tract. Serotonin metabolism, estimated by determination of the metabolite to neurotransmitter ratio, was elevated in all brain areas except for the lateral olfactory tract. These results demonstrate that following a single exposure to PCBs, there are significant changes in serotonin concentrations and metabolism in the adult rat. Furthermore, there are regional brain differences with regard to PCB concentrations and the direction and magnitude of neurochemical change induced by the PCBs.

Animals↗
PubMed1987

Trigeminal and olfactory synergism in the perception of smell.

In normal subjects olfactory evoked cortical potentials are seen with latencies of 150 m/sec and 350 m/sec. To evaluate the site of potential generators in central nervous pathways olfactory evoked cortical potentials were registered in patients with well-defined lesions of the central nervous system and the maxillary nerve. Absence of the first potential was seen in lesions of the brain-stem and the maxillary nerve. Absence of the second potential was observed in lesions of the frontal cerebral medulla and the temporal cortex. No olfactory potentials were found in circumscribed lesions of the postcentral cortex. Sites of the lesions were controlled by computed tomography. Appearance of the two potentials is correlated to normal perception of smell which is established by combined olfactory and trigeminal nerve function.

Brain Diseases↗
PubMed1990

Primary cultures of astrocytes from different brain areas of newborn rats and effects of basic fibroblast growth factor.

The effects of basic fibroblast growth factor (bFGF) on the morphology and the expression of glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) in cultured astrocytes prepared from various areas of newborn rat brain was studied. The brain was dissected in two ways, either the telencephalon (area A) and the diencephalon (area B) were dissected out of the brain (without olfactory bulbs, mesencephalon and cerebellum) or the brain was cut transversely into 3 parts (areas 1, 2 and 3). Area 1 (the anterior part) included the frontal cortex, the olfactory nuclei, the neostriatum, the accumbens nucleus and the septum; area 2 (the medial part) included the cortex, hippocampus, amygdale, thalamus and hypothalamus, and area 3 (the posterior part) included the occipital cortex, the posterior part of hippocampus and thalamus and the mamillary bodies. Essentially two different morphological aspects were observed. Most cells from areas A, 1 and 3, were flat, large, presented an irregular shape and were loosely arranged; cells from areas B and 2 were essentially polygonal in shape and closely apposed to each other. The various control cultures showed nearly the same immunostaining pattern for GFAP, but different patterns for GS. Most astroglial cells responded to bFGF and became fibrous. The GFAP immunoreaction was intense and localized in the cell bodies and processes of most cells from area A, but essentially in the processes for cells from areas 1 and 2. The immunoreactivity was weaker in cells from areas B and 3. GS-positive cells, heavily and weakly stained, were found in all treated cultures, and very strongly stained cells were located in certain zones of cultures from area A. But GS-negative cells were also seen in these treated cultures as well as in control cultures. Measurements of GS activities revealed no differences. These results indicate that astrocytes from different regions of the brain in primary culture show differences in their responsiveness to bFGF. The astroglial cells from the cerebral cortex and from the thalamus seem to present the highest and the lowest response to bFGF, respectively.

Animals↗
PubMed2006

Distribution of prodynorphin mRNA and its interaction with the NPY system in the mouse brain.

Using radioactive in situ hybridisation, the distribution of prodynorphin mRNA in the brains of C57Bl/6 mice was systemically investigated, and double-labelling in situ hybridisation was used to determine the extent to which neuropeptide Y (NPY) and prodynorphin mRNAs were co-expressed. Our results demonstrate that prodynorphin mRNA expression in the mouse brain is localised at specific subregions of the olfactory bulb, cortex, hippocampus, amygdala, basal ganglia, thalamus, hypothalamus, mesencephalon and myelencephalon. Among the regions displaying the most intense labelling were the olfactory tubercle, lateral septum (LS), caudate putamen (Cpu), central amygdaloid nucleus (Ce), paraventricular hypothalamic nucleus (PVN), supraoptic nucleus (SO), lateral hypothalamic area (LHA), ventromedial hypothalamic nucleus (VMH), lateral reticular nucleus (LRt) and solitary tract nucleus (NTS). In the arcuate nucleus of the hypothalamus (Arc), double-labelling in situ hybridisation revealed that prodynorphin expressing neurons also contained NPY mRNA, with a co-localisation rate of approximately 88% in the lateral part of the Arc, and 79% in the dorsal part of the Arc, respectively, suggesting potential overlapping functions of these two neurotransmitters in feeding type behaviour.

Animals↗