α(1B)-adrenoceptor subtype mediating the phenylephrine-induced contractile response in rabbit corpus cavernosum penis

Katsuo Furukawa*, Russell Chess-Williams, Toshimitsu Uchiyama

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

15 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)325-331
Number of pages7
JournalJapanese Journal of Pharmacology
Volume71
Issue number4
DOIs
Publication statusPublished - 1 Jan 1996
Externally publishedYes

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