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Electrophysiological properties of neurones with CGRP‐like immunoreactivity in rat dorsal root ganglia
Author(s) -
Lawson S. N.,
McCarthy P. W.,
Prabhakar E.
Publication year - 1996
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19960212)365:3<355::aid-cne2>3.0.co;2-3
Subject(s) - biology , dorsum , electrophysiology , neuroscience , anatomy , calcitonin gene related peptide , dorsal root ganglion , neuropeptide , receptor , biochemistry
Intracellular voltage recordings and fluorescent dye injections were made in vitro in 107 neurons in lumbar dorsal root ganglia (DRGs) of 6‐ to 8‐week‐old rats. Calcitonin gene‐related, peptide‐like immunoreactivity (CGRP‐LI) was examined in these neurones, which were divided into C‐, Aδ‐, and Aα/β‐fibre neurones on the basis of their conduction velocities (CVs). A‐fibre neurones with CGRP‐LI had significantly longer mean action potential (AP) and afterhyperpolarisation (AHP) durations than those without CGRP‐LI. Aδ neurones with CGRP‐LI had significantly longer AHP durations, slower CVs, and slower maximal fibre following frequencies than those without CGRP‐LI. They also had longer AP durations (not significant). The largest Aδ neurones were CGRP‐LI negative, whereas the smaller cells were either positive or negative. Aα/β neurones with CGRP‐LI also had longer mean APs (not significant) and AHPs (significant) than those without CGRP‐LI, and the cell size distributions were similar for positive and negative neurones. Most A‐fibre neurones with CGRP‐LI had inflections on the falling phase of the somatic AP. Of the A‐fibre neurones with such inflections (A i neurones), those with CGRP‐LI had longer AP durations (not significant) and longer AHP durations (significant) than A i neurones without CGRP‐LI, pointing to a functionally distinct subgroup of A i neurones. There were no significant differences in electrophysiological properties or cell size measurements between C‐fibre neurones with and without detectable CGRP‐LI. The patterns of electrophysiological properties of Aδ neuronal somata with CGRP‐LI and of most, but not all, Aα/β neuronal somata with CGRP‐LI are similar to those reported for cutaneous nociceptors with A fibres in rat (Ritter and Mendell [1992] J. Neurophysiol. 68: 2033–2041). Because rat DRG neurones that express CGRP normally also express trkA (Averill et al. [1995] Eur. J. Neurosci. 7: 1484–1494), the properties described here of neurones with CGRP‐LI are probably the same as those of DRG neurones with trkA. © 1996 Wiley‐Liss, Inc.

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