Biomedical subjects

J Broman

Publications and source records attributed to J Broman.

At least 19 recordsLinked to original sources

PubMed2004

Central projections of sensory innervation of the rat superior sagittal sinus.

The central projections of the rat superior sagittal sinus (SSS) sensory innervation were studied by transganglionic tract tracing techniques. Cholera toxin subunit b (CTb) or wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was applied on the overlying dura of the SSS and labeled terminations in the brainstem and cervical spinal cord were examined under the light microscope. Labeled cell bodies were seen bilaterally in the trigeminal ganglia and in the C2 dorsal root ganglia following both CTb and WGA-HRP applications. In the brainstem, labeled terminations were mainly found in the caudal and interpolar parts of the spinal trigeminal nucleus. In the CTb cases, terminations were also found in the dorsolateral part of the cuneate nucleus. In the spinal cord, labeled terminations were primarily located in the most ventrolateral part of the C1-C3 spinal dorsal horns on both sides. WGA-HRP labeled terminations were mainly located in laminae I and II, whereas CTb-labeled terminations located in laminae III and IV. These results indicate that the sensory information from the SSS is transmitted through both trigeminal and cervical spinal nerve branches to a primary sensory nervous center that extends from the C3 dorsal horn until to the interpolar part of the spinal trigeminal nucleus.

Afferent Pathways↗

PubMed2001

Quantitative analysis of immunogold labeling indicates low levels and non-vesicular localization of L-aspartate in rat primary afferent terminals.

The role of L-aspartate as an excitatory neurotransmitter in primary afferent synapses in the spinal cord dorsal horn is disputed. To further investigate this issue, we examined the presence of aspartate-like immunoreactivity in primary afferent nerve terminals and other tissue components of the dorsal horn. We also examined the relationship between aspartate and glutamate immunogold labeling density and the density of synaptic vesicles in primary afferent terminals and presumed inhibitory terminals forming symmetric synapses. Weak aspartate immunosignals, similar to or lower than those displayed by presumed inhibitory terminals, were detected in both C-fiber primary afferent terminals in lamina II (dense sinusoid axon terminals, identified by morphological criteria) and in A-fiber primary afferent terminals in laminae III-IV (identified with anterograde transport of choleragenoid-horseradish peroxidase conjugate). The aspartate immunogold signal in primary afferent terminals was only about one-fourth of that in deep dorsal horn neuronal cell bodies. Further, whereas significant positive correlations were evident between synaptic vesicle density and glutamate immunogold labeling density in both A- and C-fiber primary afferent terminals, none of the examined terminal populations displayed a significant correlation between synaptic vesicle density and aspartate immunogold labeling density. Thus, our results indicate relatively low levels and a non-vesicular localization of aspartate in primary afferent terminals. It is therefore suggested that aspartate, rather than being a primary afferent neurotransmitter, serves a role in the intermediary metabolism in primary afferent terminals.

Animals↗

PubMed2001

Morphological features of cat cervicothalamic tract terminations in different target regions.

Using biotinylated dextran amine to label cervicothalamic tract terminations of cats, three types of terminal arrangements were recognized. The ventral posterior lateral nucleus contains the largest proportion of the cervicothalamic tract terminals (79%) and most (72%) of these are type I terminals (form compact clusters of 5-30 boutons). In contrast, type II (form less compact clusters of 3-10 boutons) and type III (widely spaced boutons along thin axons) terminals dominate in the medial nucleus of the posterior complex (78%) and in the ventral periphery of the ventrobasal complex (86%). In the magnocellular medial geniculate nucleus, type I terminals (38%) are found close to medially located clusters of Cat-301 immunoreactive neurons, whereas type II and type III terminals locate in the surrounding Cat-301-negative regions. These findings indicate a high degree of synaptic security in the transmission between cervicothalamic tract fibers and neurons in the ventral posterior lateral nucleus and highlight the role of this nucleus in faithful transmission of cervicothalamic tract input to the cerebral cortex. Also, the Cat-301-positive neurons in the magnocellular medial geniculate nucleus may faithfully transmit cervicothalamic tract signals. The domination of type II and type III terminals in the medial nucleus of the posterior complex and in the ventral periphery of the ventrobasal complex indicates a more divergent cervicothalamic input to these regions, in line with the large receptive fields and multimodal responses of neurons in the posterior complex.

Animals↗

PubMed1998

Cervicothalamic tract termination: a reexamination and comparison with the distribution of monoclonal antibody Cat-301 immunoreactivity in the cat.

The distribution of cervicothalamic tract (CTT) terminations, labeled with anterogradely transported tracers (WGA-HRP or biotinylated dextran amine) injected into the lateral cervical nucleus of cats, was compared with the distribution of immunoreactivity for a cell-surface antigen detected with the monoclonal antibody Cat-301. The most abundant CTT termination is present in the ventrobasal complex (VB), mainly in its lateral part (VPL) and only sparsely in its medial part (VPM). In the VPL, the CTT preferentially terminates in a Cat-301-sparse peripheral rim of the nucleus and in between its lateral and medial subdivisions (VPLI and VPLm). CTT terminations are sparse in the central Cat-301-dense parts of the VPL. In the ventral periphery of VB (VBvp), situated in between the VPL/VPM and the external medullary lamina, thin CTT fibers with spaced varicosities is seen among the large fibers of passage. The VBvp is essentially devoid of Cat-301 immunoreactivity. Scattered clusters of CTT termination are also seen caudal and dorsal to the VB in the medial division of the posterior complex (POm), which is virtually devoid of Cat-301 immunoreactivity. In the caudal thalamus, dense and focused CTT termination is present in the medial extension of the magnocellular medial geniculate nucleus (MGmc) but absent from its main lateral part. The termination in the MGmc is centered upon clusters of cells displaying dense Cat-301 immunoreactivity. The present study demonstrates previously unrecognized or unconfirmed CTT terminations in the VPM and in the VBvp, and confirm previously described projections to the VPL, POm and MGmc. The preferential termination of the CTT in the Cat-301-sparse peripheral region of the VPL demonstrates that the CTT is related to a chemically defined VPL compartment. In the light of previous data, this observation suggests that the CTT is related to one or more thalamocortical channels that are partly or completely separate from that (those) activated through the dorsal column-medial lemniscal pathway. The organization of the thalamocortical channel(s) activated through the CTT remains to be elucidated. In contrast to the termination in the VPL, CTT termination in the medial MGmc is focused to clusters of Cat-301 immunolabeled cells. The significance of this difference between CTT recipient cells in the VPL and in the MGmc is unclear.

Animals↗

PubMed1996

The cervicothalamic tract terminates in Cat301-sparse regions of the cat VPL.

The termination pattern of the cervicothalamic tract (CTI), labelled with anterogradely transported WGA-HRP, was compared with the immunolabelling pattern obtained with the monoclonal antibody Cat301 in adjacent sections through the ventral posterolateral nucleus (VPL). CTT terminations are located in peripheral parts of the medial and lateral parts of the VPL (VPLm and VPL1), being more extensive in the caudal than in the rostral parts of the subnuclei, and in the dorsal part of VPL1 and dorsolateral part of VPLm, regions that are all sparse in CAt301 immunoreactivity. Central regions of the VPL with dense Cat301 immunolabelling contain only very sparse CTT termination. Thus, our findings show that the CTT innervates a compartment of the VPL that is characterized by sparse Cat301 immunoreactivity.

Animals↗

PubMed1996

The raccoon lateral cervical nucleus: mediolateral organization of GABA-positive and GABA-negative neurons and fibers.

In the lateral cervical nucleus (LCN) of the cat, GABA-immunoreactive neurons and substance P-immunoreactive fibers are concentrated in the medial part of the nucleus, whereas in the monkey LCN no preferential locations have been identified. In raccoons, substance P-immunoreactive fibers display a distribution pattern similar to that in cats. However, the presence and distribution of GABA-immunoreactive neurons in the raccoon LCN has not been examined, and it is therefore not known whether raccoons are similar to cats or primates in this respect. Thus, in the present study, the raccoon LCN was examined for the presence and distribution of GABA-immunoreactive cells with respect to their numbers, locations, and sizes. The distribution of GABA-positive fibers and varicosities within the LCN was also investigated. The results of measurements of cross-sectional areas of LCN neurons indicate a trend toward decreasing cell size along the dorsolateral to medial axis of the raccoon LCN. Compared to neurons of the centrally located ventromedial division, neurons are statistically significantly larger in the dorsolateral division and smaller in the medial division of the nucleus. Cell counts in post-embedding-stained semithin sections through the nucleus revealed an average of 8,700 neurons per LCN. Approximately 4% of LCN neurons are GABA-immunoreactive. These neurons are small and most (80%) of them are located in the medial third of the LCN. In contrast, GABA-immunoreactive fibers and varicosities are present in about equal density throughout the raccoon LCN. Thus, the distributions of GABA-immunoreactive neurons and neuron sizes in the raccoon LCN conform closely to those in cats. Together with previous observations in cats and raccoons, the present findings support the notion that these small GABA-immunoreactive neurons may be local circuit inhibitory neurons and indicate the presence of a mediolateral segregation that may be of fundamental importance for the functional organization of the carnivore LCN.

Animals↗

PubMed1996

Evidence for glutamate as a neurotransmitter in spinothalamic tract terminals in the posterior region of owl monkeys.

Previous studies have suggested that glutamate is a neurotransmitter in ascending somatosensory pathways to the thalamus. The present study examined with quantitative immunohistochemical methods the presence of glutamate in spinothalamic tract terminals of owl monkeys (Aotus trivirgatus). Such terminals in the posterior region, in which a nucleus was recently identified as a specific pain and temperature relay in macaques and humans, were labeled by anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, injected into the spinal dorsal horn. Glutamate-like immunoreactivity was demonstrated with a postembedding immunogold procedure using a well-characterized glutamate antiserum. Quantitative analysis of the immunogold labeling demonstrated that the spinothalamic tract terminals contained more than twice the tissue average of glutamate-like immunoreactivity. Enrichment of glutamate-like immunoreactivity was also found in terminals of presumed cortical origin. Presynaptic dendrites, cell bodies and non-vesicle-containing dendrites displayed low levels of glutamate-like immunoreactivity. A strong positive correlation (r = 0.69; P < 0.0001) was found between the density of synaptic vesicles and the density of gold particles in spinothalamic tract terminals, in contrast to a weak negative relationship (r = -0.28; P = 0.089) present in GABAergic presynaptic dendrites. These data provide strong evidence that the gold labeling in the spinothalamic tract terminals represents transmitter labeling, implying that glutamate is a neurotransmitter for ascending nociceptive and thermoreceptive information in primates.

Animals↗

PubMed1995

Immunocytochemical evidence for vesicular storage of glutamate in cat spinocervical and cervicothalamic tract terminals.

The densities of synaptic vesicles and gold particles, signaling fixed glutamate, were examined in spinocervical and cervicothalamic tract terminals. Statistically significant positive correlations between these parameters were detected in both terminal populations, whereas presumed inhibitory profiles displayed insignificant or negative correlations. These findings indicate a vesicular storage of glutamate in spinocervical and cervicothalamic tract terminals, and thus provide further evidence for glutamate as a neurotransmitter in the spinocervicothalamic pathway.

Animals↗

PubMed1995

Evidence for glutamate as neurotransmitter in trigemino-and spinothalamic tract terminals in the nucleus submedius of cats.

The nucleus submedius in the medial thalamus of cats is an important termination site for lamina I trigemino-and spinothalamic tract (TSTT) neurons, many of which are nociceptive-specific, and the nucleus submedius has been proposed to be a dedicated nociceptive substrate involved in the affective aspect of pain. In the present study, the distribution of glutamate was examined by immunocytochemical methods in order to evaluate the possible role of this amino acid as a neurotransmitter in TSTT terminals in the nucleus submedius. TSTT terminals were identified by anterograde transport of horseradish peroxidase and wheatgerm agglutinin-horseradish peroxidase conjugate from the spinal cord or the medullary dorsal horn. Quantitative analysis of immunogold labelling revealed that TSTT terminals contain about twice the tissue average of glutamate-like immunoreactivity. A strong positive correlation was found between the density of synaptic vesicles and the density of gold particles in these terminals, whereas no relationship was seen between these variables in GABAergic presynaptic dendrites. Enrichment of glutamate-like immunoreactivity (approximately 250% of the tissue average) was also observed in terminals of presumed cortical origin. Presynaptic dendrites and neuron cell bodies in the nucleus submedius were found to contain relatively low levels of glutamate-like immunoreactivity, at or below the tissue average. These observations provide evidence that glutamate is a neurotransmitter in lamina I TSTT terminals in the nucleus submedius. The findings also suggest glutamatergic neurotransmission between cortical afferents and nucleus submedius neurons. Glutamate is therefore likely to be an important mediator of nociceptive processing in the medial thalamus.

Animals↗

PubMed1994

Evidence for vesicular storage of glutamate in primary afferent terminals.

The correlation between the density of gold particles signalling fixed glutamate and the density of synaptic vesicles was examined in primary afferent terminals in the rat dorsal horn. Statistically significant positive correlations between these parameters were found in lamina I and III-V primary afferent terminals, identified through axonal transport of choleragenoid-horseradish peroxidase conjugate, and in lamina II dense sinusoid axon terminals of presumed thin calibre primary afferent origin. Profiles containing pleomorphic synaptic vesicles displayed negative or statistically insignificant correlations between the density of synaptic vesicles and that of gold particles. These observations indicate that primary afferent terminals store glutamate in synaptic vesicles and provide further evidence for a role of glutamate as a primary afferent neurotransmitter.

Animals↗

PubMed1994

Compartmentation of glutamate and glutamine in the lateral cervical nucleus: further evidence for glutamate as a spinocervical tract neurotransmitter.

Previous observations indicate that spinocervical tract terminals contain relatively high levels of glutamate. To examine whether these high glutamate levels are likely to represent a neurotransmitter pool or an elevated metabolic pool, the distributions of glutamate- and glutamine-like immunoreactivities were examined in adjacent immunogold-labeled sections of the lateral cervical nucleus. Spinocervical tract terminals were identified by anterograde transport of horseradish peroxidase and wheat germ agglutinin-horseradish peroxidase conjugate from the spinal cord. Spinocervical tract terminals were found to contain significantly higher levels of glutamate-like immunoreactivity than other examined tissue compartments (large neuronal cell bodies, terminals with pleomorphic vesicles, astrocytes, and average tissue level). In contrast, the highest levels of glutamine-like immunoreactivity were detected in astrocytes. The different analyzed tissue elements formed three groups with respect to glutamate:glutamine ratios: one high ratio group including spinocervical tract terminals, a second group with intermediate ratios consisting of neuronal cell bodies and terminals containing pleomorphic synaptic vesicles, and a third low ratio group including astrocytes. Our findings indicate the presence of a compartmentation of glutamate and glutamine in the lateral cervical nucleus, similar to that postulated in biochemical studies of the central nervous system. The results also show that spinocervical tract terminals have high glutamate: glutamine ratios, similar to those previously observed in putative glutamatergic terminals in the cerebellar cortex. Thus, spinocervical tract terminals display biochemical characteristics that would be expected of glutamatergic terminals and the present findings therefore provide further evidence for glutamate as a spinocervical tract neurotransmitter.

Animals↗

PubMed1994

Neurotransmitters in subcortical somatosensory pathways.

Investigations during recent years indicate that many different neuroactive substances are involved in the transmission and modulation of somesthetic information in the central nervous system. This review surveys recent developments within the field of somatosensory neurotransmission, emphasizing immunocytochemical findings. Increasing evidence indicates a widespread role for glutamate as a fast-acting excitatory neurotransmitter at different levels in somatosensory pathways. Several studies have substantiated a role for glutamate as a neurotransmitter in primary afferent neurons and in corticofugal projections, and also indicate a neurotransmitter role for glutamate in ascending somatosensory pathways. Other substances likely to be involved in somatosensory neurotransmission include the neuropeptides. Many different peptides have been detected in primary afferent neurons with unmyelinated or thinly myelinated axons, and are thus likely to be directly involved in primary afferent neurotransmission. Some neurons giving rise to ascending somatosensory pathways, primarily those with cell bodies in the dorsal horn, are also immunoreactive for peptides. Recent investigations have shown that the expression of neuropeptides, both in primary afferent and ascending tract neurons, may change as a result of various kinds of peripheral manipulation. The occurrence of neurotransmitters in intrinsic neurons and neurons providing modulating inputs to somatosensory relay nuclei (the dorsal horn, the lateral cervical nucleus, the dorsal column nuclei and the ventrobasal thalamus) is also reviewed. Neurotransmitters and modulators in such neurons include acetylcholine, monoamines, GABA, glycine, glutamate, and various neuropeptides.

Afferent Pathways↗

PubMed1993

Enrichment of glutamate-like immunoreactivity in primary afferent terminals throughout the spinal cord dorsal horn.

Although several lines of evidence indicate that glutamate is a neurotransmitter in primary afferent terminals, controversies exist on the proportion and types of such terminals that release glutamate. In the present study quantitative analysis of immunogold labelling was used to assess the presence of glutamate-like immunoreactivity in primary afferent terminals in laminae I-V of the rat spinal cord dorsal horn. Anterograde transport of choleragenoid-horseradish peroxidase from a spinal ganglion and tetramethyl benzidine histochemistry were used to identify primary afferent terminals in laminae I and III-V. Presumed C-fibre terminals in lamina II were identified on morphological criteria (dense sinusoid axon terminals). Primary afferent terminals in all dorsal horn laminae displayed significantly higher levels of glutamate-like immunoreactivity than pleomorphic vesicle-containing profiles in laminae III-IV and large neuronal cell bodies in laminae III-V. The density of gold particles over primary afferent terminals also significantly exceeded the average density of gold particles over laminae II and III-IV. The highest densities of gold particles were present over dense sinusoid axon terminals in lamina II. These findings suggest that glutamate, alone or in combination with other neuroactive compounds, is involved in the transfer of all sensory modalities from primary afferent fibres to dorsal horn neurons.

Afferent Pathways↗

PubMed1993

Substance P-like and serotonin-like immunoreactivity in the lateral cervical nucleus of the raccoon.

The distribution of substance P and serotonin in the lateral cervical nucleus (LCN) of the raccoon was examined by light microscopic immunohistochemistry. Substance P-immunoreactive fibers were found to be clustered in the ventromedial part of the LCN, whereas only few such fibers appeared in the dorsolateral part of the nucleus. This organization is closely similar to that previously observed in the cat, and provides further evidence for an anatomic and functional segregation along the transverse axis of the LCN in carnivores. In some sections, substance P-positive fibers were found primarily in areas of the ventromedial LCN containing small neurons, indicating that such fibers may be involved in functions of the LCN associated with nociceptive projection neurons and/or local circuit neurons. The raccoon LCN also received a relatively sparse innervation of serotonin-positive fibers that were distributed throughout the nucleus, an organization similar to that previously observed in the cat. The functional role of the serotonergic fibers is unclear. However, their presence suggests that descending influences on transmission in the spinocervicothalamic pathway, in addition to the well-documented descending control of spinocervical tract neurons, may be present also at the level of the LCN.

Animals↗

PubMed1993

Serotoninergic innervation of the dorsal column nuclei and its relation to cytoarchitectonic subdivisions: an immunohistochemical study in cats and monkeys (Aotus trivirgatus).

The serotoninergic innervation of the dorsal column nuclei (DCN) was investigated in cats and owl monkeys (Aotus trivirgatus) with immunohistochemical methods. A dense network of serotonin-immunoreactive fibers was present in the reticular regions of DCN in cats, and in the pars triangularis of the cuneate nucleus and the peripheral and caudal regions of the gracile nucleus in owl monkeys. The cat's cluster regions and the monkey's rotund regions were more sparsely innervated. Electron microscopic examination showed that the labeled fibers were thin and unmyelinated. Vesicle-containing, terminal-like structures were small. They were in contact with dendrites, other terminals and cell bodies, but synapses were rare. The results demonstrate that the serotoninergic projection to the DCN in both cats and owl monkeys is heterogeneously distributed in a pattern that is faithfully related to the cytoarchitectonic subdivisions of the DCN. The densely innervated reticular regions in the DCN of cats and the corresponding regions in monkeys are predominantly involved in the processing of sensory information to the cerebellum, either directly, or indirectly through projections to the inferior olive, pontine gray, tectum, pretectum, red nucleus, or zona incerta. Thus, the present findings suggest that the serotoninergic innervation of the DCN is primarily related to the DCN's involvement in motor functions.

Animals↗

PubMed1992

Lamina I spinocervical tract terminations in the medial part of the lateral cervical nucleus in the cat.

The terminations of spinocervical tract fibers in the lateral cervical nucleus (LCN) of the cat were examined with anterogradely transported Phaseolus vulgaris leucoagglutinin (PHA-L) in order to analyze their organization relative to the most medial part and the main body (the lateral two-thirds) of the LCN, which have differential projections and physiological characteristics. Iontophoretic injections of PHA-L in laminae I-V of the spinal dorsal horn yielded dense labeling in somatotopically appropriate regions of the main body of the LCN, and, as seen previously with horseradish peroxidase, additional terminations were present in the medial LCN after injections at either cervical or lumbar spinal levels. The morphological characteristics of the PHA-L labeling in these two parts of the LCN were different. Terminations in the lateral LCN consisted of dense clusters of thick fibers bearing large numbers of boutons. The terminal axons in the medial part of the LCN displayed a reticulated network of longitudinally oriented, fine fibers with well-spaced varicosities. Some of the fine fibers in the medial LCN appeared to be collaterals of thicker fibers that terminated in the lateral LCN. Injections of PHA-L that were restricted to lamina I resulted in terminal labeling only in the medial LCN. The labeling was more sparse than that observed in the medial LCN after larger dorsal horn injections but displayed the same morphological characteristics. Lamina I terminations were seen in the medial LCN after cervical or lumbar injections on both the ipsilateral and contralateral sides. The PHA-L observations were corroborated by the presence of many retrogradely labeled lamina I cells at both cervical and lumbar spinal levels, following injections of cholera toxin subunit b or rhodamine-labeled microspheres in the medial LCN. In addition, double-immunofluorescent labeling for PHA-L and substance P was performed in a few cases, since substance P immunoreactivity is present in fibers in the medial LCN and also in cell bodies in lamina I; however, very few spinocervical fibers displayed immunoreactivity for both antigens. These observations indicate that the medial part of the LCN receives input from lamina I neurons, and probably from lamina III-V neurons as well, at cervical and lumbar spinal levels. The lamina I input to the medial LCN provides a basis for the small population of nociceptive neurons that differentiate the medial LCN. The lamina I input could also be responsible for the general inhibition of lateral LCN neurons by wide-field noxious stimulation, via activation of GABAergic interneurons in the medial LCN.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1992

Electron microscopic identification of lamina I axon terminations in the nucleus submedius of the cat thalamus.

Ascending lamina I axons were labeled with Phaseolus vulgaris leucoagglutinin and the synaptic connections of their terminals in nucleus submedius (Sm) were studied in the electron microscope. The terminals were large, contained rounded synaptic vesicles, and were involved in complex synaptic aggregations with pre- and postsynaptic dendrites. It was observed that clustered large boutons from a single axon could contact a single dendritic shaft. These observations support a sensory role for lamina I input to Sm.

Animals↗

PubMed1992

Cervicothalamic tract terminals are enriched in glutamate-like immunoreactivity: an electron microscopic double-labeling study in the cat.

The distribution of glutamate-like immunoreactivity (Glu-LI) in the thalamic ventral posterolateral nucleus (VPL) of cats was studied with the EM immunogold technique in order to identify nerve terminal populations that may use glutamate as a neurotransmitter. The investigation was focused on cervicothalamic tract (CTT) terminals, which were labeled by WGA-HRP transported anterogradely from injection sites in the lateral cervical nucleus (LCN). The amount of Glu-LI in different profiles was evaluated quantitatively by counting the number of gold particles and then calculating the areal density of gold particles over different profile types. The highest density of gold particles was found over terminals with morphologic characteristics of terminals of cortical origin (RS terminals), a finding that further supports the glutamatergic nature of these terminals suggested by previous studies. Enrichment of Glu-LI was also found in CTT terminals and in non-peroxidase-labeled terminals with the same morphologic characteristics as CTT terminals (RL terminals). The labeling density over these terminals was about twice the average tissue density of gold particles. The labeling density over large VPL neuronal cell bodies was on average 127%, and that over vesicle-containing dendritic appendages and truncs (presynaptic dendrites) about 80%, of the average tissue density of gold particles. Immunogold labeling with antiserum against glutamine (Gln) indicated low levels of Gln-like immunoreactivity in CTT terminals and a high Glu:Gln ratio as compared to astrocytes and the average Glu:Gln ratio in the VPL. The present findings provide further support for a transmitter role of glutamate in terminals of ascending somatosensory afferents to the VPL, including the CTT. Taken together with previous findings of an enrichment of Glu-LI in terminals of the spinocervical tract (Broman et al., 1990), our results suggest that synaptic transmission in the spinocervicothalamic pathway is dependent on the release of glutamate both at the levels of the LCN and the VPL.

Animals↗