TY - JOUR
T1 - α(1B)-adrenoceptor subtype mediating the phenylephrine-induced contractile response in rabbit corpus cavernosum penis
AU - Furukawa, Katsuo
AU - Chess-Williams, Russell
AU - Uchiyama, Toshimitsu
PY - 1996/1/1
Y1 - 1996/1/1
N2 - The α1-adrenoceptor subtype mediating contraction to phenylephrine in rabbit corpus cavernosum penis (CCP) was investigated using selective α1-adrenoceptor subtype antagonists. WB4101 ((2-(2,6-dimethoxy-phenoxyethyl)-aminomethyl-1,4-benzodioxane) hydrochloride), 5-methylurapidil and tamsulosin concentration-dependently produced a parallel rightward shift of the concentration-response curve to phenylephrine, yielding pK(B) values of 8.05, 7.59 and 9.21, respectively. The slopes of the Schild plots were not different from unity. These antagonists did not affect the maximum response to phenylephrine. Oxymetazoline (1 μM), which initially caused a small contraction, produced a parallel rightward shift of the concentration-response curve to phenylephrine with an apparent pK(B) value of 6.99. However, oxymetazoline seemed to act as a non-surmountable antagonist to the phenylephrine-induced contraction, reducing the maximum response by 71.1%. Chloroethylclonidine (25 and 100 μM) produced a parallel rightward shift of the concentration-response curve to phenylephrine without altering the maximum response. These results show that the α1-adrenoceptor in rabbit CCP has a relatively low affinity for WB4101, 5-methylurapidil, tamsulosin and oxymetazoline and is sensitive to inactivation by chloroethylclonidine. It is suggested that the α1-adrenoceptor subtype mediating contraction to phenylephrine in rabbit CCP has the characteristics of the α(1B)-adrenoceptor subtype.
AB - The α1-adrenoceptor subtype mediating contraction to phenylephrine in rabbit corpus cavernosum penis (CCP) was investigated using selective α1-adrenoceptor subtype antagonists. WB4101 ((2-(2,6-dimethoxy-phenoxyethyl)-aminomethyl-1,4-benzodioxane) hydrochloride), 5-methylurapidil and tamsulosin concentration-dependently produced a parallel rightward shift of the concentration-response curve to phenylephrine, yielding pK(B) values of 8.05, 7.59 and 9.21, respectively. The slopes of the Schild plots were not different from unity. These antagonists did not affect the maximum response to phenylephrine. Oxymetazoline (1 μM), which initially caused a small contraction, produced a parallel rightward shift of the concentration-response curve to phenylephrine with an apparent pK(B) value of 6.99. However, oxymetazoline seemed to act as a non-surmountable antagonist to the phenylephrine-induced contraction, reducing the maximum response by 71.1%. Chloroethylclonidine (25 and 100 μM) produced a parallel rightward shift of the concentration-response curve to phenylephrine without altering the maximum response. These results show that the α1-adrenoceptor in rabbit CCP has a relatively low affinity for WB4101, 5-methylurapidil, tamsulosin and oxymetazoline and is sensitive to inactivation by chloroethylclonidine. It is suggested that the α1-adrenoceptor subtype mediating contraction to phenylephrine in rabbit CCP has the characteristics of the α(1B)-adrenoceptor subtype.
UR - http://www.scopus.com/inward/record.url?scp=0029793495&partnerID=8YFLogxK
U2 - 10.1254/jjp.71.325
DO - 10.1254/jjp.71.325
M3 - Article
C2 - 8886930
AN - SCOPUS:0029793495
SN - 0021-5198
VL - 71
SP - 325
EP - 331
JO - Japanese Journal of Pharmacology
JF - Japanese Journal of Pharmacology
IS - 4
ER -