Biomedical subjects

H Ellenberger

Publications and source records attributed to H Ellenberger.

4 recordsLinked to original sources

PubMed1997

Distribution of N-methyl-D-aspartate and non-N-methyl-D-aspartate glutamate receptor subunits on respiratory motor and premotor neurons in the rat.

Glutamate is required for the transmission of inspiratory drive in respiratory premotor and motor neurons. The glutamate receptors (GluRs) responsible for this essential function have yet to be anatomically characterized. We mapped the GluR subtypes expressed by respiratory premotor and motor neurons by using combined immunohistochemistry and retrograde labeling in adult rats. Phrenic motoneurons and bulbospinal ventral respiratory group (VRG) neurons were retrogradely labeled and immunolabeled with subunit-specific antibodies against the N-methyl-D-aspartate (NMDA) receptor subtype (NMDAR1) and the non-NMDA receptor subtypes, alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA; GluR1, GluR2/3, GluR4) and kainate (GluR5-7). Phrenic motoneurons and bulbospinal VRG neurons showed positive immunolabeling for all five GluR subunits. These results support the hypothesis that NMDA and non-NMDA receptor subtypes underlie the excitation of bulbospinal VRG neurons and phrenic motoneurons. Furthermore, immunolabeling for each receptor subtype demonstrated a unique distribution along the neuronal membrane. Immunoreactivity for AMPA receptor subunits was distributed throughout somata and proximal dendrites, NMDAR1 subunit immunolabeling was localized to somata, and GluR5-7 subunit immunolabeling was confined largely to dendrites. The differential distribution of AMPA, kainate, and NMDA receptors on the somal and dendritic surface of respiratory neurons suggests that the location of glutamatergic synapses along the neuronal surface is an important determinant of glutamate-mediated postsynaptic currents. Consequently, different patterns of glutamatergic excitation of respiratory neurons could be achieved by selective activation of different profiles of GluR subtypes on different portions of the neuronal membrane.

Animals↗

PubMed1983

The location of chronotropic cardioinhibitory vagal motoneurons in the medulla of the rabbit.

Vagal preganglionic motoneurons originating in nucleus ambiguus (NA) and dorsal vagal nucleus (DVN) were identified via retrograde labeling with horseradish peroxidase (HRP). DVN and NA were then explored for cardiovascular responsive sites using microstimulation. Stimulation within DVN from slightly caudal to obex to 3.00 mm rostral to obex produced a primary bradycardia (n = 15, X = -123 bpm). Stimulation within NA from slightly rostral to obex to 1.5 mm caudal to obex produced a similar primary bradycardia (n = 15, X = -127 bpm). Extracellular recordings were made from 7 cells in DVN and 10 cells in NA in regions producing maximal bradycardia to electrical stimulation. These cells were antidromically activated by cervical vagus nerve (VN) stimulation, increased their firing rates to systemic injection of phenylephrine (PE), revealed an expiratory rhythm, showed an increase in firing rate coinciding with spontaneous and elicited decreases in heart rate, had conduction velocities in the A-delta and B-fiber range, and produced bradycardia upon stimulation through the recording electrode with thresholds as low as 4 microA. The data indicate that in rabbits, chronotropic cardioinhibitory vagal motoneurons are discretely localized on the lateral, caudal portions of DVN and NA between 0.5 mm caudal and 1.5 mm rostral to obex.

Animals↗

PubMed1983

[Not Available].

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History, Modern 1601-↗

PubMed1981

Parabrachial area as mediator of bradycardia in rabbits.

This study examined the role of the parabrachial nucleus (PBN) in the mediation of bradycardia and in the reception of barosensory information. The 82 rabbits in the investigation were anesthetized with ethyl carbamate. Train stimulation of medial or lateral PBN produced primary bradycardia (mean peak change: -74 beats/min) associated with a pressor response (average peak mean change: +10 mm Hg) of longer latency. Section of the cervical vagus nerves indicated that the bradycardia was mediated primarily by the parasympathetic nervous system. Heart rate and blood pressure responses to train stimulation did not vary systematically as a function of respiratory pattern; paralyzing animals with decamethonium hydrochloride and artificially ventilating them also did not influence the cardiovascular responses to stimulation. Single-pulse stimulation of PBN in conjunction with extracellular single neuron recording established that neurons originating in or projecting through PBN project to the commissural region of nucleus tractus solitarius (NTS) where synapse is made neurons receiving barosensory input. In addition to establishing the existence of descending functional projections passing from PBN to NTS, injections of HRP into PBN revealed direct descending anatomical projections to PBN from regions of the forebrain previously implicated in the mediation of bradycardia. These included central nucleus of amygdala, lateral preoptic region, medial, forebrain bundle, bed nucleus of stria terminalis, anterior and lateral hypothalamus and zona incerta. The present investigation also indicated that PBN receives barosensory information. Single-pulse electrical stimulation of the aortic nerve (AN) activated neurons in NTS at an average latency of 7.5 ms and in PBN at a mean latency of 12.1 ms. Mean latency of 9 neurons in NTS activated antidromically by PBN stimulation was 3.4 ms. Conduction velocity of the monosynaptic fibers projecting from NTS to PBN was approximately 3.5 m/s, which would be characteristic of finely myelinated fibers. Injection of HRP into PBN confirmed the existence of direct ascending projections to PBN from regions of NTS (e.g. lateral commissural area) previously shown to receive primary barosensory input. However, the finding that only 1 of 9 NTS neurons antidromically activated by PBN stimulation also received barosensory stimulation, indicates that additional study is needed of the mono- and oligosynaptic functional projections from NTS to PBN. The present study did provide evidence that PBN both receives barosensory information at short latency over a direct route, and serves as a relay for descending projections mediating bradycardia.

Amygdala↗