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Shawn Hochman - One of the best experts on this subject based on the ideXlab platform.
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Axon fiber composition in paravertebral ganglia and related labeling in spinal cord.
2013Co-Authors: Amanda L. Zimmerman, Michael Sawchuk, Shawn HochmanAbstract:A. Lower power image of two caudal sympathetic ganglia and connecting nerve bridge showing nerve contains a mixture of at least 3 neurochemically distinct fiber populations: HB9-GFP+ sympathetic preganglionic neurons (SPNs), CGRP+ visceral afferents, and TH+ sympathetic postganglionics. Boxed regions are enlarged in B and C. B. Enlargement showing SPNs (GFP+), CGRP and TH immunolabeled axons in axon bundle between two ganglia. Image represents composite of 73 consecutive confocal images taken at 0.38 µm optical section thickness (27.74 µm total thickness). C. Enlargement of SPNs (GFP+), CGRP and TH immunolabeling in the left sympathetic ganglion. Section in central region of ganglia shows that, while SPNs appear to form basket-like synapses around postganglionics, CGRP+ afferents do not project through this region. Image is a collapsed stack of 11 consecutive confocal images (4.18 µm total). D. CGRP (red) and HB9-GFP labeling (green) in a transverse section of thoracic spinal cord. Note predominant CGRP labeling in the dorsal horn. HB9-GFP labeling of SPNs in the Intermediolateral Nucleus and motoneurons (MNs) in the ventral horn are identified on the right side. Middle panel shows CGRP labeling extending ventrally including into the Intermediolateral Nucleus (at arrow) while right panel provides a higher magnification image showing CGRP labeling intermingled with SPNs in the Intermediolateral Nucleus as well as along its medially oriented SPN projections. Scale bar is 100 µm in A, 20 µm in B and C, and 50 µm in D.
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Heterogeneity of Membrane Properties in Sympathetic Preganglionic Neurons of Neonatal Mice: Evidence of Four Subpopulations in the Intermediolateral Nucleus
Journal of Neurophysiology, 2009Co-Authors: Amanda Leah Zimmerman, Shawn HochmanAbstract:Spinal cord sympathetic preganglionic neurons (SPNs) integrate activity from descending and sensory systems to determine the final central output of the sympathetic nervous system. The Intermediolateral column (IML) has the highest number and density of SPNs and, within this region, SPN somas are found in distinct clusters within thoracic and upper lumbar spinal segments. Whereas SPNs exhibit a rostrocaudal gradient of end-target projections, individual clusters contain SPNs with diverse functional roles. Here we explored diversity in the electrophysiological properties observed in Hb9-eGFP–identified SPNs in the IML of neonatal mice. Overall, mouse SPN intrinsic membrane properties were comparable with those seen in other species. A wide range of values was obtained for all measured properties (up to a 10-fold difference), suggesting that IML neurons are highly differentiated. Using linear regression we found strong correlations between many cellular properties, including input resistance, rheobase, time constant, action potential shape, and degree of spike accommodation. The best predictor of cell function was rheobase, which correlated well with firing frequency–injected current (f–I) slopes as well as other passive and active membrane properties. The range in rheobase suggests that IML neurons have a recruitment order with stronger synaptic drives required for maximal recruitment. Using cluster analysis, we identified at least four subpopulations of SPNs, including one with a long time constant, low rheobase, and high f–I gain. We thus propose that the IML contains populations of neurons that are differentiable by their membrane properties and hypothesize they represent diverse functional classes.
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Heterogeneity of Membrane Properties in Sympathetic Preganglionic Neurons of Neonatal Mice: Evidence of Four Subpopulations in the Intermediolateral Nucleus
Journal of neurophysiology, 2009Co-Authors: Amanda Zimmerman, Shawn HochmanAbstract:Spinal cord sympathetic preganglionic neurons (SPNs) integrate activity from descending and sensory systems to determine the final central output of the sympathetic nervous system. The intermediola...
H Sequeira - One of the best experts on this subject based on the ideXlab platform.
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Activation of ventrolateral medullary neurons projecting to spinal autonomic areas after chemical stimulation of the central Nucleus of amygdala: a neuroanatomical study in the rat.
Brain Research, 2001Co-Authors: N. Salomé, S Leman, O Viltart, H SequeiraAbstract:Several studies have shown that the central Nucleus of amygdala is involved in cardiovascular regulation. The control of this function may be mediated by activation of the ventrolateral medulla neurons that project to preganglionic neurons located in the Intermediolateral Nucleus of the spinal cord. The aim of the present study was to examine whether stimulation of the central Nucleus of amygdala activated ventrolateral medulla neurons projecting to the Intermediolateral Nucleus. For this purpose, the injection of a retrograde tracer, the cholera toxin b subunit (CTb), into the Intermediolateral Nucleus of the T2 segment was combined with immunohistochemical detection of Fos protein following chemical stimulation of the central Nucleus of amygdala. Results showed that retrogradely labeled neurons were found throughout the ventrolateral medulla. Moreover, chemical stimulation of the central Nucleus of amygdala induced: (1) a decrease of arterial blood pressure; (2) an expression of Fos protein mainly in sub-populations of neurons located in the intermediate and caudal parts of the ventrolateral medulla; (3) a significantly higher number of double labeled neurons (CTb-immunoreactive/Fos-immunoreactive) in the rostral part of the ventrolateral medulla than in the other parts of this region. These results show that the central Nucleus of amygdala influences the activity of brainstem neurons projecting to the Intermediolateral Nucleus. Data were discussed in terms of descending amygdalofugal pathways involved in the hypotension.
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Expression of Fos protein in adrenal preganglionic neurons following chemical stimulation of the rostral ventrolateral medulla of the rat.
Brain Research, 2000Co-Authors: S Leman, O Viltart, H SequeiraAbstract:The ventrolateral medulla is known to be involved in the regulation of arterial blood pressure, especially via its connections with sympathetic preganglionic neurons (SPNs) mainly located in the Intermediolateral Nucleus of the spinal cord. It has been shown that stimulation of the rostral part of the ventrolateral medulla (RVLM) elicits a release of catecholamines from the adrenal medulla. The aim of the present study was to demonstrate the existence of a functional pathway between the RVLM and adrenal SPNs using the combination of a retrograde tract tracing technique (cholera toxin B subunit) with the immunohistochemical detection of Fos protein following the chemical stimulation of RVLM. The data obtained showed that: (1) chemical stimulation of the RVLM induced Fos immunoreactivity in the Intermediolateral Nucleus and particularly in SPNs projecting to the adrenal medulla; (2) along the thoracic segments T2-T12, 26.1% of retrogradely identified adrenal SPNs were Fos-immunoreactive with the greatest percentage (30.9%) in the T8 segment. These results favored a functional control of the RVLM on adrenal SPNs which may contribute to a substantial activation of the cardiovascular system via the release of adrenal catecholamines.
Tanemichi Chiba - One of the best experts on this subject based on the ideXlab platform.
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The synaptic structure of PACAP immunoreactive axons in the Intermediolateral Nucleus of the rat
Neuroscience letters, 1996Co-Authors: Tanemichi Chiba, Koichi Tanaka, H Tatsuoka, S.l. Dun, N.j. DunAbstract:Immuno-electronmicroscopic studies were performed to detect the presence and features of synaptic contacts between pituitary adenylate cyclase activating polypeptide immunoreactive (PACAP-ir) axons and cholera toxin B-horseradish peroxidase labeled preganglionic sympathetic neurons (PSNs) in the Intermediolateral Nucleus of the rat thoracic spinal cord. PACAP-ir axon varicosities, which contained small clear and large core synaptic vesicles, were found to form asymmetric type of synaptic contacts with dendrites and infrequently with somata of labeled preganglionic neurons. The present study provides ultrastructural evidence of PACAP-ir synaptic contacts with PSNs, raising the possibility that the peptide may function as a transmitter/modulator to these neurons.
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Phosphate-activated glutaminase immunoreactive synapses in the Intermediolateral Nucleus of rat thoracic spinal cord.
Neuroscience, 1993Co-Authors: Tanemichi Chiba, Takeshi KanekoAbstract:A monoclonal antibody against phosphate-activated glutaminase was used to identify glutamatergic neuronal components in the Intermediolateral Nucleus of the thoracic spinal cord of the rat. Under electron microscopy of the Intermediolateral Nucleus, most glutaminase immunoreactivity was detected in the axoplasm surrounding spherical synaptic vesicles in the presynaptic axon varicosities which formed asymmetric synapses with small dendrites and occasionally with neuronal cell bodies. About 40% of axon varicosities within the Intermediolateral Nucleus and 49% of the axon varicosities forming asymmetric synaptic contacts showed glutaminase immunoreactivity. Glutaminase immunoreactivity was further seen in mitochondria of neuronal perikarya and dendrites in the Intermediolateral Nucleus, and occasionally in the cytoplasm of the dendrites and glial processes in the vicinity of glutaminase-immunoreactive axon varicosities. By the combined method of immunocytochemistry and retrograde axonal transport, glutaminase-immunoreactive axons were shown to make direct synaptic contacts with the preganglionic sympathetic neurons, which were retrogradely labeled by injection of horseradish peroxidase conjugated with choleratoxin B subunit into the superior cervical ganglion. The present results indicate that glutaminase-containing axons are the major synaptic inputs to Intermediolateral Nucleus neurons including preganglionic sympathetic ones, suggesting that glutamate is used as the neurotransmitter to control those neurons in the Intermediolateral Nucleus.
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Membrane properties and dendritic arborization of the Intermediolateral Nucleus neurons in the guinea-pig thoracic spinal cord in vitro
Journal of the autonomic nervous system, 1993Co-Authors: Hiroe Inokuchi, Tanemichi Chiba, S. Masuko, M. Yoshimura, C. Polosa, Syogoro NishiAbstract:Abstract The morphological and electrophysiological properties of neurons in the Intermediolateral Nucleus (IML) were studied in the transverse and longitudinal slice of guinea-pig thoracic spinal cord (T2-T3) using intracellular staining and recording techniques. Two morphologically different types of neurons were observed: fusiform cells with craniocaudally oriented dendrites, and multipolar cells with dendrites diffusely extending in the IML. The ratio of fusiform to multipolar cells was 4:1. The fusiform cells were identified as sympathetic preganglionic neurons (SPNs) by their antidromic responses to stimulation of the ventral root exit zone, while the multipolar cells were not antidromically activated by stimulation of this site. Both cell types showed similar resting membrane potential and input resistance. The tonic responses of these neurons to hyperpolarizing current pulses were characteristically different: the SPNs had a marked hyperpolarizing sag at the break of the pulse, caused by an A current, while the unidentified neurons showed no A current. In addition, the SPNs had much longer duration of spike and afterhyperpolarization, as well as lower frequency of spontaneous or current-evoked firing, than the unidentified neurons. These observations suggest that, in the absence of the criterion of antidromic activation by stimulation of the axon, it is still possible to differentiate SPNs from other IML neurons on the basis of morphological and electrophysiological properties of the neuron.
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Immuno-electronmicroscopic studies on the gamma-aminobutyric acid and glycine receptor in the Intermediolateral Nucleus of the thoracic spinal cord of rats and guinea pigs.
Journal of the autonomic nervous system, 1991Co-Authors: Tanemichi Chiba, Reiji SembaAbstract:Gamma-aminobutyric acid (GABA) and glycine are known as major inhibitory neurotransmitters in the Intermediolateral Nucleus of the spinal cord. Distribution and density of GABA immunoreactive axon varicosities and glycine receptor immunoreactive dendrites and somata in the Intermediolateral Nucleus were examined by immuno-electronmicroscopy. GABA immunoreaction was observed in the axon varicosities of axo-dendritic and axo-somatic synapses. Glycine receptor immunoreaction was seen in association with the postsynaptic membrane of dendrites and soma. GABA immunoreactive axon varicosities were larger (1.01 ± 0.49 × 1.20 ± 0.38 μm) than axon varicosities presynaptic to glycine receptors (0.72 ± 0.22 × 0.98 ± 0.33 μm). The density of GABA immunoreactive axon varicosities was 3.65/100 μm2 and that of glycine receptor immunoreactive synapses was 4.78/100 μm2. A subpopulation of GABA immunoreactive axons (42%) made synaptic contact with glycine receptor immunoreactive dendrites or soma, indicating the coexistence of GABA and glycine.
Donald J. Reis - One of the best experts on this subject based on the ideXlab platform.
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Rostral ventrolateral medulla: a source of the glutamatergic innervation of the sympathetic Intermediolateral Nucleus.
Brain research, 1991Co-Authors: Shaun F. Morrison, Janie Callaway, Teresa A. Milner, Donald J. ReisAbstract:Abstract To determine whether the sympathoexcitatory projection from the rostral ventrolateral medulla (RVL) to the sympathetic Intermediolateral Nucleus (IML) of the spinal cord might use glutamate as an excitatoru transmitter, we performed a dual-label, transport and immunocytochemical ultrastructural study. Axon terminals within the IML were examined to determine whether anterogradely transported Phaseolus vulgaris -leucoagglutinin (PHA-L) following injections into the RVL, was colocalized with glutamate immunoreactivity using an antibody to hemocyanin-conjugated l -glutamate (Hepler et al., J. Histochem. Cytochem. , 36 (1988) 13–22). Transported PHA-L was visualized with the peroxidase-antiperoxidase technique while glutamate-like immunoreactivity was localized within the same section of the thoracic spinal cord with immunoautoradiography. By light microscopy, PHA-L immunoreactivity was found within a plexus of fine fibers and varicose processes localized to the IML. Silver grains indicative of glutamate immunoreactivity were concentrated over the IML and also over the superficial layers of the dorsal horn. Electron microscopic analysis revealed PHA-L immunoreactivity in axons and axon terminals within the IML. They ranged in diameter from 0.5 to 2.0 μm, contained numerous small clear and 0–3 large, dense-core vesicles, and formed primarily asymmetric synaptic contacts on small dendrites of IML neurons. Some of the PHA-L immunoreactive terminals making asymmetric (excitatory) synaptic contacts on the small dendrites of IML neurons also contained glutamate-like immunoreactivity. We conclude that at least a portion of the input to the IML from the RVL uses glutamate as its transmitter. These findings provide ultrastructural support for the hypothesis that the release of glutamate onto neurons in the IML plays a key role in the regulation of arterial pressure by reticulospinal, sympathoexcitatory pathways from the RVL.
S Leman - One of the best experts on this subject based on the ideXlab platform.
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Activation of ventrolateral medullary neurons projecting to spinal autonomic areas after chemical stimulation of the central Nucleus of amygdala: a neuroanatomical study in the rat.
Brain Research, 2001Co-Authors: N. Salomé, S Leman, O Viltart, H SequeiraAbstract:Several studies have shown that the central Nucleus of amygdala is involved in cardiovascular regulation. The control of this function may be mediated by activation of the ventrolateral medulla neurons that project to preganglionic neurons located in the Intermediolateral Nucleus of the spinal cord. The aim of the present study was to examine whether stimulation of the central Nucleus of amygdala activated ventrolateral medulla neurons projecting to the Intermediolateral Nucleus. For this purpose, the injection of a retrograde tracer, the cholera toxin b subunit (CTb), into the Intermediolateral Nucleus of the T2 segment was combined with immunohistochemical detection of Fos protein following chemical stimulation of the central Nucleus of amygdala. Results showed that retrogradely labeled neurons were found throughout the ventrolateral medulla. Moreover, chemical stimulation of the central Nucleus of amygdala induced: (1) a decrease of arterial blood pressure; (2) an expression of Fos protein mainly in sub-populations of neurons located in the intermediate and caudal parts of the ventrolateral medulla; (3) a significantly higher number of double labeled neurons (CTb-immunoreactive/Fos-immunoreactive) in the rostral part of the ventrolateral medulla than in the other parts of this region. These results show that the central Nucleus of amygdala influences the activity of brainstem neurons projecting to the Intermediolateral Nucleus. Data were discussed in terms of descending amygdalofugal pathways involved in the hypotension.
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Expression of Fos protein in adrenal preganglionic neurons following chemical stimulation of the rostral ventrolateral medulla of the rat.
Brain Research, 2000Co-Authors: S Leman, O Viltart, H SequeiraAbstract:The ventrolateral medulla is known to be involved in the regulation of arterial blood pressure, especially via its connections with sympathetic preganglionic neurons (SPNs) mainly located in the Intermediolateral Nucleus of the spinal cord. It has been shown that stimulation of the rostral part of the ventrolateral medulla (RVLM) elicits a release of catecholamines from the adrenal medulla. The aim of the present study was to demonstrate the existence of a functional pathway between the RVLM and adrenal SPNs using the combination of a retrograde tract tracing technique (cholera toxin B subunit) with the immunohistochemical detection of Fos protein following the chemical stimulation of RVLM. The data obtained showed that: (1) chemical stimulation of the RVLM induced Fos immunoreactivity in the Intermediolateral Nucleus and particularly in SPNs projecting to the adrenal medulla; (2) along the thoracic segments T2-T12, 26.1% of retrogradely identified adrenal SPNs were Fos-immunoreactive with the greatest percentage (30.9%) in the T8 segment. These results favored a functional control of the RVLM on adrenal SPNs which may contribute to a substantial activation of the cardiovascular system via the release of adrenal catecholamines.