EFFECT OF OMEGA-AGATOXIN-IVA ON AUTONOMIC NEUROTRANSMISSION

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Authors
  1. Lundy, P.M.
  2. Frew, R.
Corporate Authors
Defence Research Establishment Suffield, Ralston ALTA (CAN)
Abstract
Omega-Agatoxin-IVA, a peptide from the venom of the funnel-web spider Agelenopsis aperta and a P type Ca2+ channel inhibitor, was examined for effects on responses to nerve stimulation in isolated autonomic neuroeffector preparations from the rabbit, guinea-pig and rat. Ca2+ -dependent, tetrodotoxin sensitive, noradrenergic excitatory responses of rabbit pulmonary artery, rat vas deferens, and anococcygeus muscles, and cholinergic guinea-pig myenteric plexus (all highly sensitive to the N type Ca2+ channel inhibitor omega-conotoxin-GVIA) were unaffected by omega-agatoxin-IVA (100 nM). Similarly, the neurogenic response of rat bladder, which has cholinergic, and non-adrenergic non-cholinergic (NANC) excitatory components, and the NANC inhibitory response of rat jejunum (atropine 0.5 mu M- and guanethidine 5.0 mu M-treated), which are partially sensitive and insensitive to omega-conotoxin-GIVA, respectively, were unaffected by omega-agatoxin-IVA (100 nM). Neurogenic NANC inhibitory responses of the guinea-pig taenia caecum, and rat anococcygeus muscles (atropine- and guanethidine-treated, and tone raised with prostaglandin F2a), were also insensitive to omega-agatoxin-IVA. These results suggest that P type Ca2+ channels, if present, play an insignificant role in supplying the Ca2+ necessary for neurotransmitter release in the peripheral autonomic nervous system.
Keywords
P type calcium channels;N channels;Agatoxin-IVA;Conotoxin-GVIA;Calcium channel inhibitors;Neurotransmitter release;Nerve terminals;Ca2+ translocation;Funnel web spider;Agelenopsis aperta
Report Number
DRES-OL-93-16 — Reprint
Date of publication
17 May 1994
Number of Pages
8
Reprinted from
European Journal of Pharmacology, no 261, 1994, p 79-84
DSTKIM No
95-03637
CANDIS No
152704
Format(s):
Document Image stored on Optical Disk;Hardcopy

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