Possible site of action of 2-methylserotonin in inducing relaxation of acetylcholine-induced contraction in the molluscan (Mytilus edulis) smooth muscle.
1. The present study investigated the presence of 5-HT3 receptor using 2-methylserotonin (2-Me-5-HT) in the smooth muscle of Mytilus ABRM. 2. 2-Me-5-HT relaxed the acetylcholine-induced contraction in a dose-dependent manner ranging from 10(-6) to 3 x 10(-4) M (pD2 = 5.55 +/- 0.32). 3. 2-Me-5-HT-induced relaxation was antagonized by 3 x 10(-5) M ketanserin in a competitive manner (pA2 = 5.14 +/- 0.1), but not by cypropheptadine, mianserin, MDL 72222 or ICS 205-930 at a concentration of 3 x 10(-5) M. 4. 2-Me-5-HT (3 x 10(-4) M) did not alter the content of cyclic AMP and cyclic GMP in the ABRM. 5. These findings suggested that the 2-Me-5-HT-induced relaxation was mediated through 5-HT2-like receptors and was not linked to cyclic AMP or GMP systems, and, further, that 5-HT3 receptor subtype was not present in the ABRM.
Department of Physiology and Anatomy, Nihon University College of Pharmacy, Chiba, Japan.
H
H
Murakami
Y
Y
Kizawa
M
M
Sano
N
N
Edamura
C
C
Maruyama
A
A
Yamazaki
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D049872:Bivalvia / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D003533:Cyproheptadine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007211:Indoles / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008803:Mianserin / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D011985:Receptors, Serotonin / Q000032:analysis* / Q000378:metabolism; D012701:Serotonin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D000077526:Tropisetron
D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014326:Tropanes; D008803:Mianserin; D003533:Cyproheptadine; D012701:Serotonin; D000077526:Tropisetron; C045918:2-methyl-5-HT; D007650:Ketanserin; D000242:Cyclic AMP; D006152:Cyclic GMP; D000109:Acetylcholine; C042253:bemesetron