Effect of apamin on responses to BRL 34915, nicorandil and other relaxants in the guinea-pig taenia caeci

BRL 34915 (4-64 X 10(-7) M), isoprenaline (0.5-32 X 10(-8) M) and nicorandil (4-64 X 10(-6) M) produced a slowly-developing relaxation of spontaneous tone of the guinea-pig taenia caeci; with no after-contraction on washout. These inhibitory responses were unaffected by apamin (10(-7) M). Adenosine...

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Published in:British journal of pharmacology Vol. 88; no. 1; p. 113
Main Authors: Weir, S W, Weston, A H
Format: Journal Article
Language:English
Published: England 01.05.1986
Subjects:
Adenosine Triphosphate - pharmacology
Animals
Antihypertensive Agents - pharmacology
Apamin - pharmacology
Bee Venoms - pharmacology
Benzopyrans - pharmacology
Cecum - drug effects
Cromakalim
Female
Guinea Pigs
In Vitro Techniques
Ion Channels - drug effects
Isoproterenol - pharmacology
Male
Muscle Relaxants, Central - pharmacology
Muscle Tonus - drug effects
Muscle, Smooth - drug effects
Niacinamide - analogs & derivatives
Niacinamide - pharmacology
Nicorandil
Norepinephrine - pharmacology
Pyrroles - pharmacology
ISSN:0007-1188
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Summary:BRL 34915 (4-64 X 10(-7) M), isoprenaline (0.5-32 X 10(-8) M) and nicorandil (4-64 X 10(-6) M) produced a slowly-developing relaxation of spontaneous tone of the guinea-pig taenia caeci; with no after-contraction on washout. These inhibitory responses were unaffected by apamin (10(-7) M). Adenosine triphosphate (0.06-2 X 10(-3) M) and noradrenaline (1-16 X 10(-7) M) produced a rapid inhibition of spontaneous tone with a prominent after-contraction, especially on washout. Both the inhibitory effect and the rebound contraction were abolished by apamin (10(-7) M). Exposure to both BRL 34915 (64 X 10(-7) M) and to nicorandil (64 X 10(-6) M) produced an increase in the 86Rb efflux rate coefficient which was unaffected by apamin (10(-7) M). Exposure to isoprenaline (32 X 10(-8) M) had no effect on the 86Rb efflux rate coefficient. Exposure to noradrenaline (16 X 10(-7) M) produced an increase in the 86Rb efflux rate coefficient which was abolished by apamin (10(-7) M). The results confirm that both BRL 34915 and nicorandil are capable of opening potassium channels in smooth muscle but show that the channel is not apamin-sensitive.
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ISSN:0007-1188
DOI:10.1111/j.1476-5381.1986.tb09477.x