TY - JOUR
T1 - Subtyping of α1-adrenoceptors responsible for the contractile response in the rat corpus cavernosum
AU - Tong, Yat Ching
AU - Cheng, Juei Tang
N1 - Funding Information:
This study was supported in part by a grant from the National Science Council of the Republic of China (NSC-86-2314-B006-052).
PY - 1997/6/13
Y1 - 1997/6/13
N2 - The subtyping of α1-adrenoceptors responsible for mediating contraction in isolated corpus cavernosum of mature male Wistar rats was studied pharmacologically. Concentration-response studies of the cavernosal smooth muscle to three agonists: methoxamine, norepinephrine and octopamine showed that methoxamine exhibited the highest potency in inducing contractile response; the respective pD2 values were: 6.22, 5.83 and 5.38. In the presence of 2-(2,6-dimethoxyphenoxyethyl)aminomethyl (WB4101), a specific antagonist for α(1A)-adrenoceptors, a parallel rightward shift of the concentration-response curve to methoxamine was observed. On the other hand, chloroethylclonidine (CEC) caused a rightward shift of the concentration-response curve to methoxamine with significant suppression of the maximum response. The pA2 value for WB4101 obtained from Schild plot was 9.03 ± 0.06 with slope (95% CL) equal to 0.955 (1.088-0.832). In the absence of extracellular calcium ions, the methoxamine-induced contraction was reduced by 92%. Ca2+-Channel blockers, nifedipine 10-6 M and diltazem 10-6 M decreased the contractile response by 18 and 23%, respectively. The present findings suggest that α(1A)-adrenoceptors are responsible for the methoxamine-induced contraction of the rat cavernosal smooth muscle.
AB - The subtyping of α1-adrenoceptors responsible for mediating contraction in isolated corpus cavernosum of mature male Wistar rats was studied pharmacologically. Concentration-response studies of the cavernosal smooth muscle to three agonists: methoxamine, norepinephrine and octopamine showed that methoxamine exhibited the highest potency in inducing contractile response; the respective pD2 values were: 6.22, 5.83 and 5.38. In the presence of 2-(2,6-dimethoxyphenoxyethyl)aminomethyl (WB4101), a specific antagonist for α(1A)-adrenoceptors, a parallel rightward shift of the concentration-response curve to methoxamine was observed. On the other hand, chloroethylclonidine (CEC) caused a rightward shift of the concentration-response curve to methoxamine with significant suppression of the maximum response. The pA2 value for WB4101 obtained from Schild plot was 9.03 ± 0.06 with slope (95% CL) equal to 0.955 (1.088-0.832). In the absence of extracellular calcium ions, the methoxamine-induced contraction was reduced by 92%. Ca2+-Channel blockers, nifedipine 10-6 M and diltazem 10-6 M decreased the contractile response by 18 and 23%, respectively. The present findings suggest that α(1A)-adrenoceptors are responsible for the methoxamine-induced contraction of the rat cavernosal smooth muscle.
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U2 - 10.1016/S0304-3940(97)00388-1
DO - 10.1016/S0304-3940(97)00388-1
M3 - Article
C2 - 9218632
AN - SCOPUS:0030610124
SN - 0304-3940
VL - 228
SP - 159
EP - 162
JO - Neuroscience Letters
JF - Neuroscience Letters
IS - 3
ER -