Neuropeptide Y and calcitonin gene-related peptide modulate voltage-gated Ca2+ channels in mature female rat paracervical ganglion neurons.
OBJECTIVE
To assess the predominant subtype of calcium channel present in neurons of the paracervical ganglia (PG) of the female rat and the ability of neuroactive peptide to modulate total calcium current.


METHODS
Whole-cell patch clamp techniques were used on isolated PG neurons to assess calcium current modulation in the presence and absence of selective calcium channel subtype inhibitors and neuropeptides. Digital imaging analysis of cells was used to determine neuronal cell size distributions within the ganglia.


RESULTS
Average PG cell diameter was 28.1 microns. Most PG neurons (64%) had an N-type calcium current that contributed 41% of the total calcium current. The low voltage-activated or T-type current was not present. Very few neurons (22%) were sensitive to the P-type calcium channel blocker omega-agatoxin IVA, and in only 10% of neurons was the calcium current sensitive to the L-type channel blocker nimodipine. Neuropeptide Y (NPY) inhibited the calcium current by 41% in 79% of the neurons, but vasoactive intestinal peptide (VIP) had no effect. Calcitonin gene-related peptide (CGRP) both increased and decreased the calcium current in separate cell populations.


CONCLUSIONS
Calcium currents in female rat PG neurons are carried primarily through N-type calcium channels with a small contribution from L- and P-type channels. An unidentified calcium channel type is also present. Modulation of the calcium current by NPY is demonstrated, and support for the presence of a local, CGRP-mediated circuit is presented.
Cohen
D P
DP
Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, USA.
Ikeda
S R
SR
Lewis
D L
DL
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000145:classification / Q000494:pharmacology; D015220:Calcium Channels / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D005071:Evoked Potentials; D005260:Female; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009478:Neuropeptide Y / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009478:Neuropeptide Y; D010455:Peptides; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D020866:omega-Conotoxin GVIA; D015740:Calcitonin Gene-Related Peptide