α_<1B>-Adrenoceptor Subtype Mediating the Phenylephrine-Induced Contractile Response in Rabbit Corpus Cavernosum Penis

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Author(s)

Abstract

The α<SUB>1</SUB>-adrenoceptor subtype mediating contraction to phenylephrine in rabbit corpus cavernosum penis (CCP) was investigated using selective α<SUB>1</SUB>-adrenoceptor subtype antagonists. WB4101 ((2-(2, 6-dimethoxy-phenoxyethyl)-aminomethyl-l, 4-benzodioxane) hydrochloride), 5-methylurapidil and tamsulosin concentration-dependently produced a parallel rightward shift of the concentration-response curve to phenylephrine, yielding pK<SUB>B</SUB> 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<SUB>B</SUB> 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 α<SUB>1</SUB>-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 α<SUB>1</SUB>-adrenoceptor subtype mediating contraction to phenylephrine in rabbit CCP has the characteristics of the α<SUB>1B</SUB>-adrenoceptor subtype.

Journal

  • The Japanese Journal of Pharmacology

    The Japanese Journal of Pharmacology 71(4), 325-331, 1996-08-01

    The Japanese Pharmacological Society

References:  33

Cited by:  2

Codes

  • NII Article ID (NAID)
    10008189311
  • NII NACSIS-CAT ID (NCID)
    AA00691188
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    00215198
  • Data Source
    CJP  CJPref  J-STAGE 
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