Biomedical subjects

A J Beitz

Publications and source records attributed to A J Beitz.

At least 73 records · Page 4Linked to original sources

PubMed1990

The effect of acute haloperidol treatment on brain proneurotensin mRNA: in situ hybridization analyses using a novel fluorescence detection procedure.

These studies describe the normal anatomical distribution of neurons containing the mRNA coding for neurotensin (proneurotensin/neuromedin N) in the rat forebrain and midbrain and examine how that distribution is altered by acute administration of the dopamine antagonist haloperidol. A novel fluorescence detection method was developed and employed with biotinylated oligonucleotides to permit the rapid, sensitive visualization of in situ hybridization. The hybridization was temperature-sensitive, eliminated by ribonuclease, and co-localized in neurotensin-immunoreactive perikarya in the midbrain. In the forebrain of control rats, proneurotensin mRNA-containing neurons were found in the dorsomedial and ventrolateral caudate/putamen, in the nucleus accumbens, in the ventral striatum including the olfactory tubercles, and in the septal nuclei. Haloperidol induced significant increases in the frequencies and distributions of hybridization-positive neurons in the striatum and septal nuclei. In the midbrain, the highest frequency of hybridization-positive neurons occurred in the substantia nigra and the superior colliculus. Prominent populations were also present in the dorsal and ventral periaqueductal gray, the oculomotor region, and the medial longitudinal fasciculus. Less prominent were populations of neurons in the dorsomedial deep mesencephalic nuclei and the ventral tegmental area. Haloperidol induced only modest increases in the frequency of pro-neurotensin mRNA-containing neurons in the ventral tegmental area, and had no effects elsewhere in the midbrain. These results show that the fluorescent detection techniques used in this analysis provide a very rapid, reliable method for localizing hybridized mRNA in the rat brain. This study also suggests that a subpopulation of striatal neurons begin to express proneurotensin mRNA in response to haloperidol treatment. This effect of haloperidol on striatal neurons contrasts with results from additional studies of enkephalin mRNA in the striatum, suggesting that the mechanisms of haloperidol stimulation may differ between neurotensin and enkephalin-containing neurons.

Animals↗

PubMed1990

Ultrastructural morphometric analysis of enkephalin-immunoreactive terminals in the ventrocaudal periaqueductal gray: analysis of their relationship to periaqueductal gray-raphe magnus projection neurons.

The periaqueductal gray plays an important role in the descending modulation of nociception. While the importance of endogenous opioids to periaqueductal gray circuits that modulate nociception is supported by many studies, the ultrastructural relationships between enkephalin-immunoreactive axon terminals and the surrounding periaqueductal gray neuropil have not been quantitated in the rat. Further, the possible interaction between enkephalin-immunoreactive axon terminals and periaqueductal gray neurons that project to the rostroventral medulla has not been described. The present study utilized electron microscopic immunocytochemistry to quantitate the normal neuronal associations of enkephalin-immunoreactive terminals in the caudal periaqueductal gray of the rat. A primary focus of this analysis was to ascertain whether any interaction exists between enkephalin-immunoreactive axon terminals and periaqueductal gray neurons that were retrogradely-labeled from the nucleus raphe magnus and adjacent medullary reticular nuclei. We examined the ventrolateral periaqueductal gray and the ventral periaqueductal gray immediately subjacent to the aqueduct and found that both the average terminal diameters and the volume fractions of enkephalin-immunoreactive terminals were very similar. In these two regions, most terminals were observed to be in close apposition to either two or three dendrites that were neither retrogradely-labeled nor enkephalin-immunoreactive, although axonal and perikaryal associations were also observed. In the ventrolateral periaqueductal gray, 22% of all enkephalin-immunoreactive terminals were adjacent to periaqueductal gray-nucleus raphe magnus and periaqueductal gray-reticular nucleus projection neurons. In the periaqueductal gray subjacent to the aqueduct, 32% of all enkephalin-immunoreactive terminals were adjacent to periaqueductal gray-nucleus raphe magnus and periaqueductal gray-reticular nucleus projection neurons. Symmetrical synapses with these retrogradely-labeled neurons were formed by 5.5% of enkephalin-immunoreactive terminals in the ventrolateral periaqueductal gray, and by 4.3% of enkephalin-immunoreactive terminals located subjacent to the aqueduct. We also noted that enkephalin-immunoreactive terminals formed symmetrical synapses with non-retrogradely-labeled, enkephalin-immunoreactive dendrites in the periaqueductal gray. Direct opioid input onto putative excitatory periaqueductal gray output neurons that are hypothesized to modulate nociception was an unexpected finding.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Immunogold labeling of Alzheimer paired helical filaments with ganglioside MAB A2B5.

The ganglioside monoclonal antibody A2B5 has previously been used at the light microscopic level to label Alzheimer neurofibrillary tangles (NFTs). Light microscopic analysis, however, could not reveal whether the A2B5 antibody-labeled NFTs or membrane fragments associated with NFTs. Therefore, we used pre-embedding immunohistochemical electron microscopy to examine A2B5 labeling of NFT. We found that the A2B5 antibody does indeed label a NFT antigen associated with the paired helical filament (PHF) structure, while no significant labeling of membranes or membrane fragments was observed. However, no clear periodicity of the immunogold label on the PHF was found.

Alzheimer Disease↗

PubMed1990

Relationship of glutamate and aspartate to the periaqueductal gray-raphe magnus projection: analysis using immunocytochemistry and microdialysis.

This study tested the hypothesis that the excitatory amino acid transmitters glutamate and/or aspartate are associated with the periaqueductal gray (PAG)-raphe magnus (NRM) projection. Retrograde neuroanatomical tracing procedures utilizing the tracers WGA-HRP or D-[3H]-aspartate were combined with immunocytochemical localization of glutamate or aspartate to determine if glutamate and/or aspartate immunostained neurons projected to the NRM. Both glutamate- and aspartate-immunoreactive cells in the PAG were found to project to the NRM. Double labeling immunocytochemichemical procedures indicated that glutamate and aspartate are co-localized in many PAG neurons, suggesting the following possibilities: (a) one of these two amino acids may serve as a precursor to the other; (b) both amino acids may be co-released from the same PAG neuron; or (c) both amino acids are present in high levels in the perikarya for metabolic purposes. At the EM level, both glutamate- and aspartate-immunoreactive terminals were identified in the NRM, strengthening the concept that both amino acids participate in synaptic transmission in this medullary nucleus. To determine if glutamate and aspartate are in fact released from PAG-NRM axons, the PAG was stimulated chemically with homocysteic acid (HCA) and amino acids were collected from the NRM using a microdialysis probe. Microinjection of HCA, but not vehicle, into the PAG resulted in the release of both glutamate and aspartate in the nucleus raphe magnus. These data suggest that both glutamate and aspartate are released from PAG fibers terminating in the NRM and provide strong support for the hypothesis that excitatory amino acids play a neurotransmitter role in the PAG-NRM pathway.

Animals↗

PubMed1989

Colocalization of taurine- and cysteine sulfinic acid decarboxylase-like immunoreactivity in the hippocampus of the rat.

It is proposed that taurine is an inhibitory neurotransmitter/neuromodulator in the CNS. The present study localized taurine-containing neurons within the rat hippocampus with the use of a monoclonal antibody against conjugated taurine (Tau2) in conjunction with an antiserum against cysteine sulfinic acid decarboxylase (CSADC), a synthesizing enzyme for taurine. Taurine-like immunoreactivity Tau-LI) and CSADC-LI were colocalized in neurons of the dentate gyrus, CA1(/CA2), CA3, and CA4. Of all the cells examined, pyramidal basket cells within the granule cell layer of the dentate gyrus were most intensely stained with both Tau2 and CSADC. Granule cells were also double-labeled with Tau-LI and CSADC-LI. Cell nuclei and dendrites in the CA1 region stained more intensely with Tau2 than somata. CSADC-LI was colocalized with Tau-LI within these neurons. Light staining with both Tau2 and the CSADC antiserum was inconsistently present in CA3 and CA4 neurons and was found to be highly dependent on the type of fixation and delay to fixation. Tau-LI was more consistently present in increased numbers of neurons in CA3 when glutaraldehyde was added to the paraformaldehyde fixative solution. Hippocampi which were immersion-fixed in paraformaldehyde following a 0-, 6-, or 24-hour postmortem delay exhibited a lack of Tau2 staining in the CA3 region in the majority of animals studied, similar to some paraformaldehyde perfusion-fixed rats. These studies suggest that taurine was present in the majority of neurons within the major cell layers of the rat hippocampus, but Tau-LI was more easily lost from neurons in the CA3 region following delay to fixation. The localization of Tau-LI in excitatory neurons such as granule cells and pyramidal cells is not consistent with its proposed inhibitory transmitter role. However, the prominent Tau2 staining in dendrites of the CA1 region provides anatomical support for the hypothesis that taurine may be released from dendrites in the CA1 region and may function as a neuromodulator of calcium flux in these pyramidal neurons.

Animals↗

PubMed1989

Ultrastructural description of taurine-like immunoreactive cells and processes in the rat hippocampus.

A monoclonal antibody against taurine conjugated to KLH was used to identify and describe taurine-like immunoreactive processes in the rat hippocampus. Tissue from perfused rats was processed for immunohistochemical visualization of taurine and embedded for electron microscopy. Representative tissue samples from three regions, the dentate gyrus, CA3, and CA1, were sectioned, examined, and photographed. In the dentate gyrus, both granule cells and pyramidal basket cells were taurine-like immunoreactive. Some axon terminals in the dentate gyrus molecular layer as well as some mossy fiber boutons in the hilus were also taurine-like immunoreactive. In the CA3 region both pyramidal neurons and glial cells were taurine-like immunoreactive A few small-diameter axon terminals in stratum radiatum and some mossy fiber boutons in stratum lucidum were taurine-like immunoreactive. In CA1, pyramidal neurons and some glia were intensely taurine-like immunoreactive. A few immunoreactive axon terminals were seen in stratum radiatum and stratum oriens. In all regions, dendritic staining predominated. Our results support the hypothesis that while taurine may act as a neurotransmitter in a small portion of hippocampal terminals, its main function is probably as a neuromodulator or ionic regulator.

Animals↗

PubMed1989

Co-localization of glutamate and tubulin in putative excitatory neurons of the hippocampus and amygdala: an immunohistochemical study using monoclonal antibodies.

Tubulin and glutamate were immunohistochemically localized in the hippocampus and amygdala of rats using monoclonal antibodies to gamma-Glu-Glu (Glu-1) and glutaraldehyde-fixed glutamate (Glu-2), respectively. Glu-2 was shown to be selectively immunoreactive for glutaraldehyde-fixed Glu using enzyme-linked immunoassays and inhibition enzyme-linked immunoassays. Glu-1 was immunoreactive with tubulin on immunoblots of brain homogenates. However, only tubulin with a glutamate carboxy-terminal appeared to be immunoreactive with Glu-1 since tubulin from Chinese hamster ovary cells was not immunoreactive on immunoblots unless the tubulin was first treated with carboxypeptidase. Intense immunocytochemical staining by Glu-1 of hippocampus and amygdala was co-localized in the same neurons as the immunocytochemical staining for glutaraldehyde-fixed Glu produced by Glu-2. The distribution of immunostaining in the brain by Glu-1 was very similar to the distribution of immunostaining produced by Glu-2. The major difference was that glutamate-like immunoreactivity, visualized by Glu-2 staining, was intense in the nuclei of neurons, while nuclei were unstained by Glu-1. The distribution of immunostaining by these monoclonal antibodies was very similar to that reported in previous studies using other antibodies to Glu. All granule cells in the area dentata of the hippocampus exhibited intense immunoreactivity with both antibodies. Immunoreactivity was also observed in the stratum lucidum of CA3, the zone of termination of mossy fiber axons of granule cells. The majority of pyramidal cells in CA1, and many pyramidal cells in CA3 of the hippocampus were immunoreactive. In addition, it appeared that all of the pyramidal cells in the subiculum exhibited immunoreactivity. Light, diffuse immunoreactivity was observed in the neuropil of the hippocampus and subiculum. Most perikarya in the amygdala were characterized by light to moderate Glu-1 immunoreactivity and moderate to intense Glu-2 immunoreactivity. Fairly intense Glu-1 and Glu-2 immunoreactivity was seen in some neurons of the lateral nucleus, basolateral nucleus, lateral subdivision of the central nucleus, and the periamygdaloid cortex. The morphology of immunostained neurons in the lateral and basolateral nuclei indicates that the majority of these cells correspond to the pyramidal class 1 neurons described in previous Golgi studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗

PubMed1989

A quantitative ultrastructural analysis of neurotensin-like immunoreactive terminals in the midbrain periaqueductal gray: analysis of their possible relationship to periaqueductal gray-raphe magnus projection neurons.

The periaqueductal gray of the rat contains significant levels of the putative peptide neurotransmitter neurotensin. The profound anti-nociceptive effects of neurotensin injected into the periaqueductal gray may involve a population of periaqueductal gray neurons having descending projections to the rostral ventral medulla, including nucleus raphe magnus and adjacent reticular nuclei. In this study, electron microscopic immunocytochemistry was used to examine the ultrastructure of periaqueductal gray axon terminals containing neurotensin-like immunoreactive material and to obtain quantitative data regarding the relationship of such terminals to other elements of the neuropil. Of particular interest was the interaction between neurotensin-like immunoreactive terminals and retrogradely labeled neurons that project to nucleus raphe magnus and adjacent reticular nuclei. Within the periaqueductal gray, the sites of retrograde and immuno-labeling were consistent with previous reports. The neurotensin-immunoreactive structures were predominantly axon fibers and terminals. In the ventrocaudal periaqueductal gray, the mean diameter of neurotensin-containing terminals was 0.93 +/- 0.02 micron and they comprised a volume fraction of 0.0010. Most of the neurotensin-positive terminals examined (74.2%) were in contact with or closely apposed to dendrites. The most common anatomical configuration observed was a single neurotensin-immunoreactive terminal juxtaposed to three dendrites. Only 2% of immunoreactive terminals were apposed to perikarya. Neurotensin-immunoreactive terminals were observed to form symmetrical synapses and 96.4% of such terminals were axodendritic. Occasional multiple neurotensin-immunoreactive terminals associated with single dendrites were observed. Although neurotensin-like immunoreactive terminals were quite prominent, only a small percentage made synaptic contact with periaqueductal gray neurons that project to the nucleus raphe magnus and adjacent reticular formation. Among the population of periaqueductal gray neurons retrogradely-labeled from nucleus raphe magnus and adjacent reticular nuclei, the frequency of direct synaptic contact by neurotensin-immunoreactive terminals was 2%. These data suggest that the periaqueductal gray circuitry by which neurotensin ultimately affects descending pathways is complex and may involve a population of local circuit neurons whose transmitters and connections remain to be elucidated.

Animals↗

PubMed1989

Production and characterization of a novel monoclonal antibody against neurotensin: immunohistochemical localization in the midbrain and hypothalamus.

We developed a mouse monoclonal antibody against neurotensin (NT), termed NT8, for applications in immunohistochemistry and for ELISA analysis of NT. The antibody's paratope was determined by competitive ELISA using several peptide fragments of NT. That paratope requires intact peptide bonds between NT residues proline-7, arginine-8, and arginine-9. The antibody is of the IgG2B sub-isotype, having an IC50 for intact NT of approximately 3 nM when measured by competitive ELISA. Light microscopic immunohistochemical studies in the periaqueductal gray (PAG) and hypothalamus demonstrated staining patterns that agreed well with previous reports. Neuron perikarya were visualized even in the absence of colchicine pre-treatment, indicating that NT8 antibody is very sensitive in immunohistochemical applications. At the EM level, the antibody stained axon terminals, dendrites, and perikarya in the PAG. In lightly immunoreactive perikarya, rough endoplasmic reticula were visualized, suggesting that biosynthetic precursors to NT might be recognized by NT8.

Animals↗

PubMed1988

Colocalization of fixative-modified glutamate and glutaminase but not GAD in rubrospinal neurons.

In an attempt to identify putative neurotransmitters of rubrospinal neurons, immunocytochemical procedures were utilized in combination with retrograde tracing techniques in 15 adult male rats. Following injections of horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to HRP (WGA-HRP) into the spinal cord, midbrain sections were processed with a combined procedure that allowed visualization of both the retrograde tracer and one or more antigens including glutamate, glutaminase, and glutamatic acid decarboxylase (GAD). Initial colocalization studies demonstrated that glutamatelike and glutaminaselike immunoreactivities were cocontained within the same neurons. Following injections of HRP or WGA-HRP into the spinal cord approximately 53% of retrogradely labeled neurons contained glutamate immunoreactivity. Triple-labeling experiments indicated that glutamatelike immunoreactivity was colocalized with glutaminase immunoreactivity in retrogradely labeled rubrospinal neurons. Retrogradely labeled neurons did not contain GAD immunoreactivity. Moreover, triple labeling experiments verified that glutamatelike immunoreactive retrogradely labeled cells did not cocontain GAD immunoreactivity. These studies demonstrate that glutamate and its synthesizing enzyme, glutaminase, are present in some rubrospinal neurons and raise the possibility that a component of the rubrospinal projection may be glutamatergic. GAD, on the other hand, is not present in rubrospinal neurons. This finding supports the hypothesis that GABAergic neurons play a role as interneurons in the red nucleus.

Animals↗

PubMed1988

Immunocytochemical localization of glutamate dehydrogenase in mitochondria of the cerebellum: an ultrastructural study using a monoclonal antibody.

Monoclonal antibodies to glutamate dehydrogenase (GDH) were produced and shown to have high degrees of specificity using immunoblots and ELISA. Immunocytochemical staining of electron microscopic preparations revealed selective intense staining of mitochondria in Bergmann glia, oligodendrocytes and astrocytes in the cerebellum of the rat. Differential intensity of staining among mitochondria within individual glial cells and between glial cells was observed and may provide an anatomical means of detecting differences in glutamate metabolism.

Animals↗

PubMed1988

Organization of glutamate-like immunoreactivity in the rat superficial dorsal horn: light and electron microscopic observations.

Glutamate has been shown to be a neurotransmitter in the central nervous system of vertebrates, and it has been hypothesized that glutamate is functional as a neurotransmitter in the spinal cord dorsal horn. A monoclonal antibody to fixative-modified glutamate was used in this study to examine the light microscopic and ultrastructural profiles of glutamate-like immunoreactivity in the superficial dorsal horn of the rat spinal cord. Glutamate-like immunoreactivity was observed in neurons, fibers, and terminals of both laminae I and II. Marginal zone immunoreactive neurons ranged from 10 to 30 micron in diameter and received many nonimmunoreactive somatic synapses. In substantia gelatinosa, immunoreactive neurons were observed in both inner and outer layers, ranged 5 to 10 micron in diameter, and received few nonimmunoreactive somatic synapses. Glutamate-like immunoreactive dendrites were observed in both laminae and were contacted primarily by nonimmunoreactive synaptic terminals that generally contained small clear vesicles. Both myelinated and unmyelinated immunoreactive axons were observed in Lissauer's tract. Immunoreactive terminals contained small (40 nm) clear vesicles and generally formed simple synaptic contacts with nonimmunoreactive dendrites in laminae I and II. The results of this study corroborate the importance of glutamate as a neurotransmitter in spinal sensory mechanisms.

Animals↗

PubMed1988

Extracellular amino acid concentrations in the dorsal spinal cord of freely moving rats following veratridine and nociceptive stimulation.

In vivo microdialysis was used to sample extracellular concentrations of amino acids in the dorsal lumbar spinal cord of freely moving rats. Changes in the extracellular concentrations of amino acids were measured in response to infusion of veratridine (180 microM), a sodium channel activator, as well as during acute noxious stimulation by an injection of 5% formalin into the metatarsal region of the hindleg. Veratridine produced a tetrodotoxin (TTX)-sensitive increase in the extracellular concentration of Glu. Concentrations of Asp, taurine, Ala, Asn, and Gly were not significantly elevated following veratridine stimulation. Intradermal injection of formalin produced a TTX-sensitive increase in Asp concentration and a non-TTX-sensitive increase in Glu concentration. These data support the hypothesis that Glu and Asp are dorsal horn neurotransmitters involved in nociception.

Amino Acids↗

PubMed1988

Glycine potentiates strychnine-induced convulsions: role of NMDA receptors.

Strychnine poisoning leads to seizures that have traditionally been attributed to competitive antagonism of glycine receptors in the spinal cord. Although glycine is thought to act as an inhibitory neurotransmitter, a strychnine-insensitive glycine (Gly2) receptor has been recently described in cultured mouse neurons that is thought to be allosterically linked to the excitatory amino acid NMDA receptor. The present study demonstrates that intrathecally administered glycine, in contrast to other putative inhibitory transmitters, potentiates rather than inhibits strychnine-induced convulsions in mice. The seizure-potentiating effects of glycine are blocked by aminophosphonovaleric acid, an NMDA antagonist. In addition, in animals pretreated with a subconvulsive dose of strychnine to block strychnine-sensitive glycine receptors (Gly1), glycine enhances, rather than inhibits, NMDA-induced convulsions. Together, these results indicate that the seizure-potentiating effects of glycine involve activation of NMDA receptors. This study provides the first evidence that glycine is capable of modulating the activity of NMDA receptors in the spinal cords of adult animals. In light of the elevated concentrations of glycine found in epileptogenic brain foci, these data also suggest that glycine may be a positive modulator in the production of epileptic seizures.

2-Amino-5-phosphonovalerate↗

PubMed1988

Colocalization of taurine- and cysteine sulfinic acid decarboxylase-like immunoreactivity in the cerebellum of the rat with monoclonal antibodies against taurine.

Two monoclonal antibodies against fixative-modified taurine, Tau1 and Tau2, were produced, characterized, and used in the present study to analyze the distribution of taurine in the cerebellum of the rat. In addition, immunohistochemical colocalization experiments were performed to determine whether cerebellar neurons contain both taurine and its synthesizing enzyme, cysteine sulfinic acid decarboxylase (CSADC). In ELISAs, both Tau1 and Tau2 displayed high affinities for taurine conjugated to various carrier proteins and possessed some cross-reactivity for other amino acids which are present in lower concentrations in the brain than taurine. Tau2 was found to recognize only taurine and hypotaurine when paraformaldehyde was used to fix the amino acids to carrier proteins. With the use of glutaraldehyde fixation, Tau1 cross-reacted with conjugates of beta-alanine and hypotaurine and Tau2 cross-reacted strongly with conjugates of cysteic acid and hypotaurine and weakly with cysteine sulfinic acid. Despite different cross-reactivities, Tau1 and Tau2 exhibited almost identical patterns of neuronal staining in bands of Purkinje cells in the cerebellum. Staining of Purkinje cell dendrites was more prominent than staining of the soma. Light immunoreactivity was present in Golgi, stellate, and basket cells. A scattered population of granule cells displayed taurine-like immunoreactivity at the electron microscopic level. Immunostaining was identified in some terminals in the Purkinje cell layer and in a limited number of mossy fibers. Tau2-like immunoreactivity was colocalized with CSADC-like immunoreactivity in the cerebellar neurons described above. These immunoreactive cells may represent a subpopulation of neurons that contain a higher concentration of taurine than neighboring cells due to their ability to synthesize taurine. The intense immunoreactive staining of Purkinje cell dendrites provides support for the hypothesis that calcium-dependent release of taurine in the cerebellum may originate primarily from dendritic rather than synaptic processes and suggests a neuromodulator role for taurine in the cerebellum.

Animals↗

PubMed1987

An ultrastructural description of glutamate-like immunoreactivity in the rat cerebellar cortex.

This study provides the first ultrastructural description of glutamate-like immunoreactive neurons and processes in the cerebellar cortex of the rat. Glutamate-like immunoreactivity was seen in parallel fibers, granule cell perikarya, Purkinje cell dendrites, and mossy fiber glomeruli. These data support previous studies that have suggested that granule cells may use glutamate as a neurotransmitter. However, not all granule cells or all parallel fibers were glutamate-like immunoreactive, suggesting that some granule cells may use transmitters other than glutamate. The presence of glutamate-like immunoreactivity in mossy fibers supports the hypothesis that some cerebellar afferent systems may use glutamate as a neurotransmitter.

Animals↗

PubMed1987

Localization of glutamate, glutaminase, aspartate and aspartate aminotransferase in the rat midbrain periaqueductal gray.

Glutamate and aspartate are putative excitatory neurotransmitters in the central nervous system. The present study utilized novel monoclonal antibodies against fixative-modified glutamate and aspartate and polyclonal antisera against the amino acid synthesizing enzymes, glutaminase and aspartate aminotransferase, to analyze the distribution of these amino acids in the rodent midbrain periaqueductal gray. Glutamate-, aspartate-, glutaminase- and aspartate aminotransferase-like immunoreactive neurons, fibers and processes are present throughout the rostrocaudal length of the periaqueductal gray. Glutamate- and glutaminase-like immunoreactive neurons displayed a similar homogeneous pattern of distribution, being localized predominantly to the lateral and dorsal subdivisions of the periaqueductal gray. Co-localization experiments suggest that glutamate and glutaminase are in fact co-contained within the same PAG neurons. Aspartate aminotransferase-like immunoreactive neurons were distributed in a pattern similar to glutamate and glutaminase with the exception that fewer cells were stained in the dorsocaudal and the rostral third of the PAG. Aspartate-like immunoreactive neurons were less numerous than glutamate-like immunoreactive cells and were located in the lateral aspect of the PAG. These results demonstrate a specific and distinct distribution of glutamate and aspartate immunoreactive neurons and support recent data suggesting that glutamate and aspartate serve as excitatory neurotransmitters in the PAG.

Animals↗

PubMed1987

The nuclei of origin of brainstem enkephalin and cholecystokinin projections to the spinal trigeminal nucleus of the rat.

The sites of origin of brain stem enkephalin and cholecystokinin projections to the rodent spinal trigeminal nucleus were studied utilizing the combined retrograde transport-peroxidase antiperoxidase immunohistochemical technique. Several brain stem areas were found to contain enkephalin-like immunoreactive double-labeled neurons following injection of wheat germ agglutinin-horseradish peroxidase or horseradish peroxidase into the spinal trigeminal nucleus. The largest numbers of enkephalin double-labeled neurons were identified in the nucleus pontis oralis, nucleus raphe medianis, medial vestibular nucleus and the midbrain periaqueductal gray. Enkephalin projections to the spinal trigeminal nucleus were also found to originate from the nucleus solitarius, nucleus raphe pallidus, nucleus raphe magnus, nucleus raphe dorsalis, nucleus reticularis paragigantocellularis, nucleus reticularis gigantocellularis pars alpha and the deep mesencephalic nucleus. In contrast to the numerous sources of enkephalin input to the spinal trigeminal nucleus, cholecystokinin projections to this region were limited to four brain stem nuclei. These included the nucleus solitarius, raphe obscurus, nucleus paragigantocellularis and the ventral reticular nucleus of the medulla. The finding that only a small number of brain stem cholecystokinin-like immunoreactive neurons project to the spinal trigeminal nucleus supports the hypothesis that most of the cholecystokinin input to the spinal trigeminal nucleus arises from primary afferent trigeminal fibers. The spinal trigeminal nucleus is known to play a role in processing sensory information and in the transmission of orofacial nociception. The present study identifies several brain stem sites which provide enkephalin and/or cholecystokinin input to the spinal trigeminal nucleus. Several of these nuclei have been implicated as components of the endogenous pain control system and the present results raise the possibility that they may modulate incoming orofacial nociception by releasing the endogenous opioid, enkephalin. Cholecystokinin, on the other hand, has been demonstrated in other studies to attenuate the action of opiates and thus may play an opposing role in the spinal trigeminal nucleus.

Animals↗