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CGRP Selectively Activates a Subpopulation of Nodose Sensory Neurons with Tonic Action Potential Firing Properties
Author(s) -
Fazan Rubens,
Lu Yongjun,
Chapleau Mark W
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.1008.16
Subject(s) - tonic (physiology) , nodose ganglion , calcitonin gene related peptide , depolarization , chemistry , neuroscience , rheobase , excitatory postsynaptic potential , sensory system , baroreceptor , endocrinology , medicine , receptor , neuropeptide , vagus nerve , biology , stimulation , heart rate , biochemistry , blood pressure
Calcitonin gene‐related peptide (CGRP) and its receptors are highly expressed in subpopulations of sensory C‐fibers innervating heart, viscera, and blood vessels including carotid sinuses. While CGRP release and its vasodilator activity have been studied extensively, little is known regarding its effects on the activity of vagal afferent and baroreceptor neurons in nodose ganglia. We hypothesized that CGRP may selectively activate a subpopulation of nodose sensory neurons. Resting membrane potential (RMP) and action potential (AP) responses to depolarizing current injection (0.1‐1.0nA for 1s) were recorded by intracellular microelectrode from neurons isolated from nodose ganglia of C57BL/6 mice. Two types of neurons were studied: 'tonic' neurons that repetitively fire APs during sustained depolarization, and 'phasic' neurons that fire only a single AP at the beginning of the period of depolarization. CGRP (500 nM) depolarized 8 of 10 tonic neurons from ‐52±2 to ‐47±2 mV and increased AP discharge from 17±2 to 29±2 spikes during the period of current injection (n=8, P<0.01). These excitatory effects were fully reversed upon drug washout. In contrast, CGRP did not change RMP or AP discharge in phasic neurons (n=6). Consistent with these findings, CGRP increased cytosolic Ca 2+ concentration (Fluo‐4) in a subset of rat nodose neurons. We conclude that CGRP selectively activates the majority of tonic nodose sensory neurons without affecting RMP or AP discharge in phasic neurons. The selectivity of the response likely reflects co‐expression of CGRP receptors with ion channels enabling repetitive spike firing in tonic neurons. (HL14388, VA)