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S J Bacon - One of the best experts on this subject based on the ideXlab platform.
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a Monosynaptic Pathway from an identified vasomotor centre in the medial prefrontal cortex to an autonomic area in the thoracic spinal cord
1993Co-Authors: S J Bacon, A D SmithAbstract:Abstract Chemical microstimulation (1 mM l -glutamate or 25 mM KCl) of the medial prefrontal cortex of anaesthetized rats produced falls in systolic and diastolic blood pressure of similar magnitude, without a change in heart rate. Application of the lectin Phaseolus vulgaris leucoagglutinin by iontophoresis from an adjacent barrel of the same micropipette revealed a direct projection to the central autonomic area of the thoracic spinal cord from this vasomotor area, which is equivalent to the region called prelimbic cortex by Krettek and Price [ J. comp. Neurol . (1977) 171 , 157–192] or Cg3 by Paxinos and Watson [ The Rat Brain in Stereotaxic Coordinates (1986)]. Labelled axons descended in the dorsal corticospinal tract in the cervical spinal cord, where they displayed a few varicosities. In the thoracic spinal cord, labelled fibres occurred bilaterally in the gray matter, predominantly in the central autonomic area, where they displayed many varicosities. Electron microscope studies revealed that the anterogradely labelled varicosities in the central autonomic area were vesicle-filled boutons that formed asymmetric synaptic contacts. The synaptic targets were small dendrites or dendritic protrusions that were characterized by a high incidence of multivesicular bodies and coated vesicles. We conclude that a Monosynaptic Pathway that originates from a physiologically-defined vasomotor area in the medial prefrontal cortex terminates on a characteristic type of neuron in the central autonomic area of the thoracic spinal cord.
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evidence of a Monosynaptic Pathway between cells of the ventromedial medulla and the motoneuron pool of the thoracic spinal cord in rat electron microscopic analysis of synaptic contacts
1991Co-Authors: A Zagon, S J BaconAbstract:Previous electrophysiological and anatomical data have suggested the existence of a descending Pathway from the ventromedial medulla into the thoracic motoneuron pool. However, systematic light and electron microscopic analysis have not yet been done to reveal such a projection. In the present study, the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L) was injected into several discrete regions of the medioventral medulla and descending PHA-L-labelled axons were investigated in the thoracic ventral horn using both light and electron microscopy. Light microscopic analysis of descending projections from 20 distinct areas of the medioventral medulla showed that neurons that project predominantly to the intermediate and ventral regions of the thoracic spinal grey matter are located caudal to the facial nucleus. Monosynaptic contacts were found between axons originating from five distinct regions of the medioventral medulla (containing raphe and/or gigantocellular reticular neurons) and cells in the thoracic motoneuron pool. PHA-L-labelled boutons formed synaptic contacts with large calibre dendrites and with somata. Seventy-two per cent of the investigated 32 boutons appeared to have symmetrical synaptic membrane specializations. The majority of the boutons contained only small, pleomorphic vesicles. Our findings show the existence of a direct Monosynaptic Pathway between the neurons of the ventromedial medulla and thoracic motor nuclei, providing anatomical support for previous physiological data.
A Zagon - One of the best experts on this subject based on the ideXlab platform.
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evidence of a Monosynaptic Pathway between cells of the ventromedial medulla and the motoneuron pool of the thoracic spinal cord in rat electron microscopic analysis of synaptic contacts
1991Co-Authors: A Zagon, S J BaconAbstract:Previous electrophysiological and anatomical data have suggested the existence of a descending Pathway from the ventromedial medulla into the thoracic motoneuron pool. However, systematic light and electron microscopic analysis have not yet been done to reveal such a projection. In the present study, the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L) was injected into several discrete regions of the medioventral medulla and descending PHA-L-labelled axons were investigated in the thoracic ventral horn using both light and electron microscopy. Light microscopic analysis of descending projections from 20 distinct areas of the medioventral medulla showed that neurons that project predominantly to the intermediate and ventral regions of the thoracic spinal grey matter are located caudal to the facial nucleus. Monosynaptic contacts were found between axons originating from five distinct regions of the medioventral medulla (containing raphe and/or gigantocellular reticular neurons) and cells in the thoracic motoneuron pool. PHA-L-labelled boutons formed synaptic contacts with large calibre dendrites and with somata. Seventy-two per cent of the investigated 32 boutons appeared to have symmetrical synaptic membrane specializations. The majority of the boutons contained only small, pleomorphic vesicles. Our findings show the existence of a direct Monosynaptic Pathway between the neurons of the ventromedial medulla and thoracic motor nuclei, providing anatomical support for previous physiological data.
A D Smith - One of the best experts on this subject based on the ideXlab platform.
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a Monosynaptic Pathway from an identified vasomotor centre in the medial prefrontal cortex to an autonomic area in the thoracic spinal cord
1993Co-Authors: S J Bacon, A D SmithAbstract:Abstract Chemical microstimulation (1 mM l -glutamate or 25 mM KCl) of the medial prefrontal cortex of anaesthetized rats produced falls in systolic and diastolic blood pressure of similar magnitude, without a change in heart rate. Application of the lectin Phaseolus vulgaris leucoagglutinin by iontophoresis from an adjacent barrel of the same micropipette revealed a direct projection to the central autonomic area of the thoracic spinal cord from this vasomotor area, which is equivalent to the region called prelimbic cortex by Krettek and Price [ J. comp. Neurol . (1977) 171 , 157–192] or Cg3 by Paxinos and Watson [ The Rat Brain in Stereotaxic Coordinates (1986)]. Labelled axons descended in the dorsal corticospinal tract in the cervical spinal cord, where they displayed a few varicosities. In the thoracic spinal cord, labelled fibres occurred bilaterally in the gray matter, predominantly in the central autonomic area, where they displayed many varicosities. Electron microscope studies revealed that the anterogradely labelled varicosities in the central autonomic area were vesicle-filled boutons that formed asymmetric synaptic contacts. The synaptic targets were small dendrites or dendritic protrusions that were characterized by a high incidence of multivesicular bodies and coated vesicles. We conclude that a Monosynaptic Pathway that originates from a physiologically-defined vasomotor area in the medial prefrontal cortex terminates on a characteristic type of neuron in the central autonomic area of the thoracic spinal cord.
E J Van Bockstaele - One of the best experts on this subject based on the ideXlab platform.
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ultrastructural analysis of rat ventrolateral periaqueductal gray projections to the a5 cell group
2012Co-Authors: Dusica Bajic, E J Van Bockstaele, Herbert K ProudfitAbstract:Abstract Stimulation of neurons in the ventrolateral periaqueductal gray (PAG) produces antinociception as well as cardiovascular depressor responses that are mediated in part by pontine noradrenergic neurons. A previous report using light microscopy has described a Pathway from neurons in the ventrolateral PAG to noradrenergic neurons in the A5 cell group that may mediate these effects. The present study used anterograde tracing and electron microscopic analysis to provide more definitive evidence that neurons in the ventrolateral PAG form synapses with noradrenergic and non-catecholaminergic A5 neurons in Sasco Sprague–Dawley rats. Deposits of anterograde tracer, biotinylated dextran amine, into the rat ventrolateral PAG labeled a significant number of axons in the region of the rostral subdivision of the A5 cell group, and a relatively lower number in the caudal A5 cell group. Electron microscopic analysis of anterogradely-labeled terminals in both rostral ( n = 127) and caudal ( n = 70) regions of the A5 cell group indicated that approximately 10% of these form synapses with noradrenergic dendrites. In rostral sections, about 31% of these were symmetric synapses, 19% were asymmetric synapses, and 50% were membrane appositions without clear synaptic specializations. In caudal sections, about 22% were symmetric synapses, and the remaining 78% were appositions. In both rostral and caudal subdivisions of the A5, nearly 40% of the anterogradely-labeled terminals formed synapses with non-catecholaminergic dendrites, and about 45% formed axoaxonic synapses. These results provide direct evidence for a Monosynaptic Pathway from neurons in the ventrolateral PAG to noradrenergic and non-catecholaminergic neurons in the A5 cell group. Further studies should evaluate if this established Monosynaptic Pathway may contribute to the cardiovascular depressor effects or the analgesia produced by the activation of neurons in the ventrolateral PAG.
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amygdalar peptidergic circuits regulating noradrenergic locus coeruleus neurons linking limbic and arousal centers
2011Co-Authors: Beverly A S Reyes, Ana Raquel Franky Gomes Carvalho, Kunal Vakharia, E J Van BockstaeleAbstract:The endogenous opioid peptides, met- or leu-enkephalin, and corticotropin-releasing factor (CRF) regulate noradrenergic neurons in the locus coeruleus (LC) in a convergent manner via projections from distinct brain areas. In contrast, the opioid peptide dynorphin (DYN) has been shown to serve as a co-transmitter with CRF in afferents to the LC. To further define anatomical substrates targeting noradrenergic neurons by DYN afferents originating from limbic sources, anterograde tract-tracing of biotinylated dextran amine (BDA) from the central amygdaloid complex was combined with immunocytochemical detection of DYN and tyrosine hydroxylase (TH) in the same section of tissue. Triple labeling immunocytochemistry was combined with electron microscopy in the LC where BDA was identified using an immunoperoxidase marker, and DYN and TH were distinguished by the use of sequential immunogold labeling and silver enhancement to produce different sized gold particles. Results show direct evidence of a Monosynaptic Pathway linking amygdalar DYN afferents with LC neurons. To determine whether DYN-containing amygdalar LC-projecting neurons colocalize CRF, retrograde tract-tracing using fluorescent latex microspheres injected into the LC was combined with immunocytochemical detection of DYN and CRF in single sections in the central amygdala. Retrogradely labeled neurons from the LC were distributed throughout the rostro-caudal extent of the central nucleus of the amygdala (CeA) as previously described. Cell counts showed that approximately 42% of LC-projecting neurons in the CeA contained both DYN and CRF. Taken with our previous studies showing Monosynaptic projections from amygdalar CRF neurons to noradrenergic LC cells, the present study extends this by showing that DYN and CRF are co-transmitters in Monosynaptic projections to the LC and are poised to coordinately impact LC neuronal activity.
Tamas L Horvath - One of the best experts on this subject based on the ideXlab platform.
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Monosynaptic Pathway between the arcuate nucleus expressing glial type ii iodothyronine 5 deiodinase mrna and the median eminence projective trh cells of the rat paraventricular nucleus
2001Co-Authors: Sabrina Diano, Frederick Naftolin, Fernando Goglia, Valer Csernus, Tamas L HorvathAbstract:Recent evidence suggests that the thyroid regulation of thyrotropin-releasing hormone (TRH)-containing neurons in the paraventricular nucleus of the hypothalamus involves the activation of other hypothalamic neural circuits. For example, the arcuate nucleus and not the paraventricular nucleus contains the highest enzyme activity of 5'-deiodinase type II, an enzyme that is pivotal for the local synthesis of T3. This experiment was undertaken to demonstrate whether a Monosynaptic Pathway exists between the arcuate nucleus and those TRH cells of the paraventricular nucleus that are neuroendocrine, i.e. project to the external layer of the median eminence. A specific cRNA probe derived from the coding region of deiodinase type II was used for the in situ hybridization histochemistry which was combined with immunocytochemistry for a specific marker of glial cells, glial fibrillary acidic protein (GFAP). The hybridization signals were present within the hypothalamus in the arcuate nucleus-median eminence region and in the periventricular area. The periventricular labeling was localized to the ependymal layer of the third ventricle and no hybridization product was detected in the paraventricular nucleus and other hypothalamic nuclei adjacent to the third ventricle. Within the median eminence, numerous cells containing the hybridization product were located in the internal layer adjacent to the floor of the third ventricle and in the external layer adjacent to the surface of the brain. In the dorso- and ventromedial regions of the arcuate nucleus, deiodinase type II mRNA-containing cells were also detected. Numerous type II deiodinase mRNA-containing cells in the median eminence and arcuate nucleus were also found to be immunopositive for GFAP. The abundance of arcuate cells expressing the hybridization product was lower than those in the periventricular region or in the median eminence. The anterograde tracer, Phaseolus vulgaris leucoagglutinin, was injected into the medial parts of the arcuate nucleus where the in situ hybridization experiment detected deiodinase type II mRNA. Simultaneously with the anterograde tracing, the retrograde tracer, Fluoro-Gold, was injected into either the median eminence or the general circulation. Light and electron microscopic double and triple immunolabeling experiments on vibratome sections of colchicine-pretreated animals revealed that arcuate fibers innervate TRH cells within the parvicellular region of the paraventricular nucleus. Populations of these TRH cells receiving afferents from the arcuate nucleus were also retrogradely labelled from either the median eminence or the general circulation indicating their direct role in the regulation of thyrotropin secretion from the anterior pituitary. The majority of arcuate nucleus efferents on TRH cells were found to establish symmetrical synaptic connections. The present results provided direct evidence of a Monosynaptic Pathway between the hypothalamic site of local thyroid hormone production, the arcuate nucleus, and neuroendocrine TRH cells in the paraventricular nucleus. This signalling modality may play an important role in thyroid feedback on TRH cells. Since the arcuate nucleus is involved in the regulation of central mechanisms controlling diverse homeostatic functions, including reproduction and feeding, the Pathway described in this study may also carry integrated signals related to reproduction and ingestion to TRH-producing cells.
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evidence for a direct neuronal Pathway from the suprachiasmatic nucleus to the gonadotropin releasing hormone system combined tracing and light and electron microscopic immunocytochemical studies
1997Co-Authors: E M Van Der Beek, Tamas L Horvath, V M Wiegant, R Van Den Hurk, Ruud M BuijsAbstract:The timing and occurrence of the preovulatory luteinizing hormone (LH) surge in the female rodent are critically dependent on the integrity of the suprachiasmatic nucleus (SCN). Destruction of the SCN leads to a cessation of the ovarian cycle, whereas implantation of estrogen in ovariectomized rats results in daily LH surges. The anatomical substrate for these effects is not known. Previous studies involving lesions of the SCN have suggested the presence of a direct vasoactive intestinal polypeptide (VIP)-containing Pathway to gonadotropin-releasing hormone (GnRH) neurons. To further investigate the direct connection between the SCN and the GnRH system, we have used tract-tracing with the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PhaL) in combination with an immunocytochemical staining for GnRH in light and electron microscopic studies. Small, unilateral PhaL deposits, especially when they were placed in the rostral ventrolateral portion of the SCN, revealed a bilateral projection to the preoptic area, where PhaL-immunoreactive fibers were regularly found in close apposition to GnRH neurons. Ultrastructural studies showed synaptic interaction of PhaL-containing fibers with GnRH-immunoreactive (IR) cell bodies, thus demonstrating a direct SCN-GnRH connection. Taken together, these data provide evidence for the existence of a Monosynaptic Pathway from the SCN to the GnRH system in the hypothalamus of the female rat. We suggest that this Pathway may contain at least VIP as a putative transmitter and may play a role in the circadian regulation of the estrous cycle in the female rat. J. Comp. Neurol. 384:569‐579, 1997. r 1997 Wiley-Liss, Inc. Indexing terms: female rat; circadian regulation; estrous cycle; synapse