Hypothermia enhances contractile responses of the guinea pig taenia caeci to acetylcholine, 5-hydroxytryptamine, caffeine and calcium.
Isometric contraction of isolated guinea-pig taenia caeci was induced with acetylcholine (ACh) and 5-hydroxytryptamine (5-HT) at 37 and 30 degrees C to investigate the effect of hypothermia on the response of smooth muscle to neurotransmitters. Lowering the temperature increased the amplitude of contraction in response to 10(-6) M ACh. Contraction in response to 10(-6) M 5-HT was also greater at 30 degrees C. 5-HT-contraction was not inhibited by atropine, but was inhibited by ketanserin. Calcium-contraction was also induced in an isosmotic high potassium solution. The amplitude of the contraction elicited by 5 x 10(-3) M Ca was significantly greater at 30 degrees C, and was inhibited by verapamil. The amplitude of the contractile response to 5 x 10(-3) M caffeine was also greater at 30 degrees C than at 37 degrees C. The finding that both calcium- and caffeine-contraction were enhanced at low temperature raises the possibility that intracellular calcium participate in cold-induced enhancement of contraction.
Nagai
M
M
Department of Physiology, Medical University of Yamanashi, Japan.
Inada
H
H
Kawabata
K I
KI
Ohura
R
R
Iriki
M
M
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002432:Cecum / Q000187:drug effects / Q000502:physiology*; D003080:Cold Temperature; D003470:Culture Media; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology*
D003470:Culture Media; D012701:Serotonin; D002110:Caffeine; D000109:Acetylcholine; D002118:Calcium