Characterization of the contractile response induced by 5-methoxytryptamine in rat stomach fundus strips.
This study examined effects of 5-methoxytryptamine (5-MOT), an agonist at 5-HT4 and 5-HT2B receptors, on the contractile response and acetylcholine release in rat stomach fundus strips. 5-MOT (10(-9)-10(-5) M) produced a concentration-dependent increase in the contraction, while it evoked acetylcholine release in a 'bell-shaped' concentration-dependent manner. Atropine reduced 5-MOT (10(-8)-10(-6) M)-induced contractions, but it had little effect on the contractions evoked by higher concentrations. 5-MOT-induced contraction and acetylcholine release were inhibited by SDZ 205-557 (2-methoxy-4-amino-5-chloro-benzoic acid 2-[diethylamino] ethyl ester), a 5-HT4 receptor antagonist. In the presence of atropine, both SDZ 205-557 and yohimbine, a 5-HT2B receptor antagonist, inhibited the contraction. In the presence of tetrodotoxin, the contraction was inhibited by yohimbine, but not by SDZ 205-557. These results suggest that the contractile action of 5-MOT in rat stomach fundus involves atropine-sensitive and atropine-resistant components. The sensitive contraction appears to be mediated through 5-HT4 receptors located on cholinergic neurons, whereas the resistant contraction is mediated through 5-HT4 receptors located on non-cholinergic neurons and through 5-HT2B receptors.
Amemiya
N
N
Department of Pharmacology, School of Medicine, Sapporo Medical University, Chuo-ku, Japan.
Hatta
S
S
Takemura
H
H
Ohshika
H
H
D010129:4-Aminobenzoic Acid / Q000494:pharmacology; D008735:5-Methoxytryptamine / Q000494:pharmacology; D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005748:Gastric Fundus; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects* / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology; D062366:para-Aminobenzoates
D062366:para-Aminobenzoates; C072790:2-methoxy-4-amino-5-chlorobenzoic acid 2-(diethylamino)ethyl ester; D015016:Yohimbine; D012701:Serotonin; D008735:5-Methoxytryptamine; D001285:Atropine; D000109:Acetylcholine; D010129:4-Aminobenzoic Acid