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Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have demonstrated the coexistence of GABA-like and tyrosine hydroxylase-like immunoreactivities (GABA-LI and TH-LI, respectively) in the same neurons of the rat locus ceruleus (LC). The profiles of these cells were labeled by alternately immunostaining adjacent sections for GABA-LI or TH-LI by the avidin-biotin-peroxidase complex method or the peroxidase-anti-peroxidase method after perfusion (either Zamboni's fixative or PPG), and observation at light and electron microscopic levels. For light microscopy, pairs of adjacent sections of more than 590 (Zamboni's) and 260 (PPG), and for electron microscopy, 40 ultrathin sections cut from adjacent semithin plastic sections (Zamboni's), were examined. GABA-LI was found in 80% (1,309/1,642 in total) of small and medium-sized neurons, uniformly scattered throughout the LC. Observations unequivocally show that the majority of GABA-ergic neurons are also noradrenergic. Several neurons are neither noradrenergic nor GABA-ergic, while other noradrenergic neurons do not show GABA-LI. It is shown that astrocytes, but not oligodendrocytes, contain GABA. In situ hybridization using a probe DNA fragment of the glutamic acid decarboxylase (GAD) cDNA, amplified by the polymerase chain reaction, detected GAD mRNA signals in many neurons throughout the LC, supporting the presence of a GAD/GABA system in the LC. Multiple "classical" transmitters, including GABA, serotonin, and noradrenaline, coexist in many LC neurons and may contribute to its widely diverging projections throughout the entire CNS.
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PMID:Immunocytochemical and in situ hybridization evidence for the coexistence of GABA and tyrosine hydroxylase in the rat locus ceruleus. 136 Jul 72

Predorsal bundle cells give rise to the major efferent pathway from the superior colliculus to the premotor centers of the brainstem and spinal cord responsible for initiating orienting movements. The activity of predorsal bundle cells is profoundly influenced by an inhibitory pathway from substantia nigra pars reticulata that uses gamma aminobutyric acid (GABA) as a neurotransmitter. The present study examines the morphological basis for this influence of substantia nigra on predorsal bundle cells in the rat. In the first experiments, the laminar distributions of the nigrotectal tract terminals and the predorsal bundle cells were compared. The predorsal bundle cells were labeled by the retrograde axonal transport of horseradish peroxidase from either the decussation of the predorsal bundle or the cervical spinal cord, while the terminations of the pathway from substantia nigra pars reticulata were labeled by anterograde axonal transport from the substantia nigra. Either horseradish peroxidase, wheat germ agglutinin conjugated to horseradish peroxidase, or Phaseolus vulgaris leucoagglutinin were used as anterograde tracers. The results showed that the distributions of both the predorsal bundle cells and the nigrotectal terminals are restricted almost entirely to the intermediate grey layer and that they overlap extensively. Predorsal bundle cells varied in size. Within the areas of maximum overlap, the majority, regardless of size, was closely apposed by nigrotectal terminals. In a second series of experiments, the synaptic contacts between nigrotectal terminals and the tectospinal component of the predorsal bundle were examined in tissue in which both the terminals and the tectospinal cells were labeled for electron microscopy. In the final experiments, the distribution and fine structure of the nigrotectal terminals were compared to those of terminals that had been labeled immunocytochemically with an antibody to glutamic acid decarboxylase, the synthesizing enzyme for GABA. The results showed that nigrotectal terminals contain large numbers of mitochondria and pleomorphic vesicles, and form synaptic contacts with the somas and proximal dendrites of tectospinal cells. These synapses have modest postsynaptic densities. In both their distribution and fine structure, these terminations resemble the glutamic acid decarboxylase immunoreactive terminals that contact tectospinal cells. Taken together, these results support the view that the nigrotectal tract is an important source of GABAergic input to most, if not all, predorsal bundle cells.
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PMID:The nigral projection to predorsal bundle cells in the superior colliculus of the rat. 137 4

The presence of a reptilian thalamic reticular nucleus was investigated in Caiman crocodilus. Injections of horseradish peroxidase made into the dorsal thalamus produced retrogradely labeled neurons in the nucleus of the dorsal peduncle of the lateral forebrain bundle. A separate population of thalamic neurons located in the nucleus of the dorsal peduncle of the lateral forebrain bundle with morphology different from those neurons projecting to the dorsal thalamus were found to be immunoreactive for glutamic acid decarboxylase. Taken together, these findings suggest that Caiman, like mammals, contain a thalamic reticular nucleus but that thalamic organization in Caiman differs significantly from that of mammals.
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PMID:A different type of vertebrate thalamic organization. 170 34

We have compared retrograde labelling of rat olivocochlear neurons after unilateral cochlear injections of wheatgerm agglutinin conjugated horseradish peroxidase (WGA-HRP) and free HRP. After cochlear injection of WGA-HRP, labelling of nerve cell bodies in the brainstem can be explained not only as conventional retrograde labelling resulting from uptake by efferent nerve terminals synapsing on or near hair cells, but also as spurious labelling originating from tracer leakage, through the periotic duct and over the eighth nerve sheaths, into the cerebral-spinal fluid. Depending on the length of survival time, spurious labelling can involve small portions of the nucleus of the trapezoid body or the entire auditory brainstem and other non-auditory centers. On the contrary, moderate amounts of free HRP delivered to the cochlea do not lead to spurious labelling. With free HRP as the tracer of choice, we found that cochlear efferent cells were located not only in the ipsilateral LSO body and bilaterally within MVPO and RPO as already described by White and Warr, but also surrounding the ipsilateral LSO and in the ipsilateral LVPO. The allocation of these newly described olivocochlear neurons to the medial large cell or lateral small cell system is uncertain because they are located laterally in the brainstem and project ipsilaterally but are large spherical to fusiform or multipolar cells. A zinc salicylate-formol fixative and a metal intensified DAB reaction were found to be effective in visualizing retrogradely transported HRP in neurons and allowed immunocytochemical staining of the same sections with antisera to glutamic acid decarboxylase and choline acetyltransferase. This double label protocol can be used to produce a neurochemical map of the OC systems.
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PMID:An evaluation of retrograde tracing methods for the identification of chemically distinct cochlear efferent neurons. 170 12

The peroxidase-antiperoxidase method was used to examine major immunohistochemical features of the spinal cord of adult raccoons. The lateral portions of the ventral horn contained many large multipolar neurons that showed cholecystokinin-like immunoreactivity, suggesting the coexistence of cholecystokinin with acetylcholine in a subset of motoneurons. The dorsal horn revealed unique but overlapping patterns of immunoreactivity for glutamic acid decarboxylase, somatostatin, substance P, vasoactive intestinal polypeptide and cholecystokinin. The data imply that some of the peptides may coexist within the same dorsal root ganglion cells and their spinal cord processes.
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PMID:Immunoreactivity for glutamic acid decarboxylase and several neuropeptides in the spinal cord of the raccoon. 170 58

We have produced a neurochemical map of the cell bodies of origin of the cochlear efferent terminals in rat by combining glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), or calcitonin gene-related peptide (CGRP) immunocytochemistry with retrograde transport of horseradish peroxidase. The locations of cochlear efferent cell bodies are in general agreement with the medial and lateral systems described by White and Warr (J. Comp. Neurol. 219:203-214, 1983) with some minor modifications. The lateral system consists of at least two pools of chemically distinct neurons located within the lateral superior olive (LSO) ipsilateral to the injected cochlea. One pool immunostains with an antibody to GAD while the other immunostains with antibodies to ChAT and to CGRP. The medial efferent system consists of periolivary neurons that are almost exclusively large and ChAT-positive but CGRP-negative. They are located both ipsilateral and contralateral to the cochlea they project to. There are a few GAD-positive small neurons in the medioventral and rostral periolivary regions that project ipsilaterally, but these may prove tobe ectopic neurons. The ipsilateral lateroventral periolivary region (LVPO) contains some efferent neurons, all of which are ChAT-positive but CGRP-negative. Additional cochlear efferent neurons, some of which are ChAT-positive and others GAD-positive, are present within and immediately dorsal to the fiber capsule surrounding the medial limb, and to a lesser extent the lateral limb, of the ipsilateral LSO. Not all GAD-positive or ChAT-positive olivary cells project to the cochlea. We have complemented the results in the brainstem by demonstrating two immunocytochemically distinct populations of efferent terminals in the cochlea simultaneously, one CGRP-positive and the other GAD-positive. Approximately equal numbers of boutons immunoreactive for both markers are present beneath inner hair cells throughout the entire length of the cochlea. Surprisingly high numbers of GAD-positive and CGRP-positive boutons are also present on outer hair cells, with each class having its spatially and morphologically distinct features. The lack of CGRP-positive periolivary cells that are retrogradely labeled by cochlear injections of HRP suggests that the lateral olivocochlear system sends projections to outer hair cells. Our results raise questions about species differences in the organization of targets of the lateral and medial olivocochlear systems.
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PMID:Chemically distinct rat olivocochlear neurons. 170 37

The synaptic organization of the mediodorsal thalamic nucleus (MD) in the rat was studied with the electron microscope, and correlated with the termination of afferent fibers labeled with wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Presynaptic axon terminals were classified into four categories in MD on the basis of the size, synaptic vesicle morphology, and synaptic membrane specializations: 1) small axon terminals with round synaptic vesicles (SR), which made asymmetrical synaptic contacts predominantly with small dendritic shafts; 2) large axon terminals with round vesicles (LR), which established asymmetrical synaptic junctions mainly with large dendritic shafts; 3) small to medium axon terminals with pleomorphic vesicles (SMP), which formed symmetrical synaptic contacts with somata and small-diameter dendrites; 4) large axon terminals with pleomorphic vesicles (LP), which made symmetrical synaptic contacts with large dendritic shafts. Synaptic glomeruli were also identified in MD that contained either LR or LP terminals as the central presynaptic components. No presynaptic dendrites were identified. In order to identify terminals arising from different sources, injections of WGA-HRP were made into cortical and subcortical structures known to project to MD, including the prefrontal cortex, piriform cortex, amygdala, ventral pallidum and thalamic reticular nucleus. Axons from the amygdala formed LR terminals, while those from the prefrontal and insular cortex ended exclusively in SR terminals. Fibers labeled from the piriform cortex formed both LR and SR endings. Based on their morphology, all of these are presumed to be excitatory. In contrast, the axons from the ventral pallidum ended as LP terminals, and those from the thalamic reticular nucleus formed SMP terminals. Both are presumed to be inhibitory. At least some terminals from these sources have also been identified as GABAergic, based on double labeling with anterogradely transported WGA-HRP and glutamic acid decarboxylase (GAD) immunocytochemistry.
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PMID:Synaptic organization of projections from basal forebrain structures to the mediodorsal thalamic nucleus of the rat. 170 22

Experiments have been performed on adult albino rats in order to study the cellular organization of the thalamic reticular nucleus. For this purpose four approaches have been used: Nissl stain, Golgi impregnation, retrograde transport of horseradish peroxidase after injection in different thalamic nuclei, and immunocytochemistry with antibodies against GABA and glutamic acid decarboxylase. In sections through the horizontal plane, three morphologically different neurons have been observed. Cells with round perikarya and with multipolar dendrites were found predominantly in the rostral pole of the nucleus. Neurons with large fusiform cell body and with dendrites arborizing mainly on the horizontal plane were detected through the whole extent of the nucleus. Small fusiform neurons were observed almost exclusively in the medial third of the dorso-ventral extent of the nucleus. The Golgi impregnation method demonstrated that dendrites of small fusiform neurons develop in the vertical plane perpendicular to the dendritic arborization of large fusiform neurons. In coronal sections neurons with round perikarya and with large fusiform cell bodies are detectable while small fusiform neurons are only rarely visible. These data have been confirmed by statistical form factor analysis. Moreover, by means of the horseradish peroxidase and the immunocytochemical study, it has been confirmed that all three groups of neurons project within the thalamus and that they are GABAergic. The data concerning the distribution within the nucleus of the three morphologically different neurons are discussed in relation to the topographic distribution of cortical sensory afferents and to the topographic maps within different sectors of the reticular nucleus.
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PMID:The reticular thalamic nucleus (RTN) of the rat: cytoarchitectural, Golgi, immunocytochemical, and horseradish peroxidase study. 170 89

GABA-synthesizing neurons were identified in the medulla of the rat by peroxidase-antiperoxidase (PAP) immunohistochemistry for glutamic acid decarboxylase (GAD). Using diaminobenzidine (DAB) either alone or intensified with silver, a relatively large number of GAD-immunoreactive neurons were evident within the reticular formation, raphe nuclei and vestibular nuclei. In all these areas, profuse GAD-immunoreactive varicosities appeared to contact the soma and dendrites of both non-GABA and GABA neurons. These observations suggest that GABA neurons may act as interneurons or local projection neurons within the medulla and accordingly exert a potent inhibitory and/or disinhibitory control on bulbar projection neurons. Within the ventral reticular formation (pars alpha and ventralis of the gigantocellular reticular field) and raphe magnus, large numbers of prominent GAD-immunoreactive neurons resembled in size and morphology and overlapped in distribution the serotonin-immunoreactive neurons of the same regions. However, by sequential double immunostaining utilizing DAB as a chromogen for serotonin (5-HT) and benzidine dihydrochloride (BDHC) for GAD, it was found that GAD-containing neurons were distinct from 5-HT-containing neurons. Following injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the upper cervical spinal cord and combined processing for WGA-HRP (using tetramethylbenzidine [TMB] with cobalt) and immunohistochemistry (with DAB), a contingent of spinally projecting neurons were found to contain GAD. The GAD-immunoreactive reticulo- and raphe-spinal neurons were most frequent within the pars alpha and ventralis of the gigantocellular reticular fields and the raphe magnus, where they were approximately equal in number to the coexistent, but distinct 5-HT spinally projecting neurons. GABA neurons of the medulla may thus contribute directly to the bulbar inhibitory influence upon spinal sensory and motor systems.
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PMID:GABA-synthesizing neurons in the medulla: their relationship to serotonin-containing and spinally projecting neurons in the rat. 172 90

The ultrastructural characteristics and synaptic organization of afferent terminals from the brainstem to the mediodorsal thalamic nucleus (MD) of the rat have been studied with the electron microscope, by means of anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). Labeled fibers were seen predominantly in the lateral portion of MD after the injections of WGA-HRP into the substantia nigra pars reticulata (SNr), the superior colliculus (SC), and the dorsal tegmental region (DT). The boutons arising from the SC were relatively small (less than 1.5 microns in diameter), formed asymmetric synaptic contacts with small dendrites and dendritic spines, and contained round synaptic vesicles. The axon terminals from the DT were mostly large boutons (2-4.5 microns) with asymmetric synaptic specializations and round vesicles. These boutons and their postsynaptic targets formed synaptic glomeruli that were entirely or partially ensheathed by glial lamellae. The ultrastructural features are almost identical to those of boutons in the medial and central segments of MD that were previously shown to originate from the basal amygdaloid nucleus and the piriform cortex. The boutons from the SNr had a wide range in size, but the majority were medium-sized to large (1.5-4 microns). The nigral boutons established symmetric synaptic contacts with dendritic shafts and occasionally with somata, and contained pleomorphic vesicles. However, like the DT terminals, they participated in glomerular formations. The nigral terminals closely resemble previously described terminals in the medial part of MD from the ventral pallidum, except that the nigral terminals formed en passant and axosomatic synapses as well as axodendritic synapses. A combined immunohistochemistry and WGA-HRP tracing study revealed that the nigral inputs were immunoreactive for glutamic acid decarboxylase and the axon terminals from the DT were immunoreactive for choline acetyltransferase. In a separate study, the colliculothalamic fibers have been shown to take up and transport the transmitter specific tracer [3H]-D-aspartate, and are therefore putatively glutamatergic and/or aspartatergic. Taken together with this, the present results suggest that the collicular afferents are excitatory and glutamatergic and/or aspartatergic, that the inputs from the DT are also excitatory and cholinergic, while the nigral inputs are inhibitory and GABAergic.
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PMID:Ultrastructure and synaptic organization of axon terminals from brainstem structures to the mediodorsal thalamic nucleus of the rat. 172 8


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