Effects of vasoactive intestinal peptide on transmission from excitatory and inhibitory nerves to smooth muscle cells in chicken rectum.
The effects of vasoactive intestinal peptide on electrical membrane properties and neuromuscular transmission, which is resistant to atropine and guanethidine, were investigated in isolated circular muscle strips from chicken rectum. Intracellular microelectrodes were used to record changes in membrane potential. Vasoactive intestinal peptide (0.2-1.0 microM) hyperpolarized the membrane of cells of the muscle strip. The mean maximal hyperpolarization produced by 1 microM vasoactive intestinal peptide was 5.3 +/- 0.4 mV. Electrotonic potentials were unchanged in amplitude and the slopes of the current-voltage curves were similar before and after application of the peptide, indicating no change in membrane resistance in the presence of the peptide. The hyperpolarizing effect was preserved in the presence of apamin. These properties of the peptide-induced hyperpolarization were shared by the inhibitory junction potential. In addition, vasoactive intestinal peptide (0.5 or 1.0 microM) markedly inhibited or abolished the inhibitory junction potential but had little effect on the excitatory junction potential. The present results suggest a possible physiological implication of this peptide as a neurotransmitter of the inhibitory neurone in chicken rectum.
Komori
S
S
Department of Veterinary Science, Faculty of Agriculture, Gifu University, Japan.
Ohashi
H
H
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002645:Chickens; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000294:innervation*; D009474:Neurons / Q000187:drug effects*; D012007:Rectum / Q000294:innervation; D013552:Swine; D009435:Synaptic Transmission / Q000187:drug effects*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D001030:Apamin; D014660:Vasoactive Intestinal Peptide