[The adrenoceptor and calcitionin-gene related peptide receptor in the striated urethral sphincter in male rabbit].

BACKGROUND The objective of this study is to analyze the adrenoceptor and calcitonin-gene related peptide receptor in the isolated striated urethral sphincter from a male rabbit. METHODS The striated urethral sphincter preparations were suspended in 2ml tissue chamber filled with Krebs Ringer solution, and the changes of isometric twitch contraction induced by electrical field stimulation (EFS-contraction) were recorded in the presence of 3-isobutyl-1-methyl-xanthine (IBMX, 10(-5) M). RESULTS The EFS-contraction was almost completely attenuated by tetrodotoxin (TTX, 10(7) M), vecronium (10(-4) M) and suxamethonium (10(-4) M). Norepinephrine (NE, 10(-8) M-10(-4) M) did not affect the EFS-contraction, but increased the tonic contraction in a dose-dependent manner. The tonic contractions induced by NE was significantly blocked by phentolamine (10(-6) M). Clonidine (10(-7) M), yohimbin (10(-7) M) and propranolol (10(-9) M-10(-6) M) did not affect the EFS-contraction. Isoproterenol (10(-9) M-10(-6) M) did not reduce the carbachol (10(-5) M) induced tonic contraction. Calcitonin-gene related paptide (CGRP, 10(-7) M-3 x 10(-6) M) did not affect the EFS-contraction and did not increase the tonic contraction. CONCLUSION These results suggested that alpha 1-adrenoceptors of the striated urethral sphincter play a role to modulate the resting tension level, but alpha 2-adrenoceptors, beta-adrenoceptors and CGRP receptors play no role in this regard.