Tachykinin-Induced Contractions in the Circular Muscle of Guinea Pig Ileumt

The Japanese Journal of Pharmacology

Nagao Suzuki¹  Ken Mizuno¹  Yasuo Gomi¹ 

[1] Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kanazawa University

关键词: Substance P;    Neurokinin A;    Neurokinin B;    Circular muscle;    Ileum (guinea pig);   

DOI  :  10.1254/jjp.65.233

学科分类：药理学

来源: Nihon Yakuri Gakkai Henshuubu / Japanese Pharmacological Society

【 摘 要 】

References(30)Cited-By(4)Actions of substance P (SP, 10-9 to 10-6 M), neurokinin A (NKA, 10-9 to 10-6 M) and neurokinin B (NKB, 10-10 to 10-6 M) in the circular muscle of guinea pig ileum were investigated in segment and strip preparations, in which methacholine produced similar contractions. In the segment preparations, three tachykinins produced repeatedly occurring twitch-like contractions. Their efficacies were similar with the same maximal contractions, but their potencies were different (NKB > NKA = SP). Latency (38 sec) was observed before the initiation of contractions in response to NKA, but not to SP or NKB. Atropine (10-6 M) and tetrodotoxin (3×10-7M) did not affect NKA-induced contractions, but inhibited SP and NKB-induced contractions; the dose-response curves for SP and NKB were rightwardly shifted by atropine. The treatment with atropine brought out latency in the responses for NKB. In the strip preparations, SP did not substantially induce contractions, but NKA and NKB produced twitch-like contractions after latent periods of 28 and 36 sec, respectively. The efficacy of NKA was similar to that in segment preparations, while that of NKB was much lower in strip preparations. Unlike in segment preparations, atropine did not inhibit contractions induced by the two tachykinins in strip preparations. These results suggest that tachykinins induce contractions through myogenic and neurogenic mechanisms, the latter of which may be inoperative in strip preparations.

【 授权许可】

Unknown