Furukawa T, Morishita H
Department of Pharmacology, School of Medicine, Fukuoka University, Japan.
Eur J Pharmacol. 1997 Jun 11;328(2-3):229-34. doi: 10.1016/s0014-2999(97)83049-x.
The effects of selective dopamine receptor agonists and antagonists on sympathetic neuromuscular transmission were investigated in the guinea-pig vas deferens in order to test for the presence of presynaptic dopamine receptors. A single-pulse field stimulus induced a rapid monophasic contraction which was strongly inhibited by alpha,beta-methylene ATP, a P2X purinoceptor desensitizing agent. The contraction was also inhibited by 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK 14,304), a selective alpha2-adrenoceptor agonist. This inhibition was antagonized by idazoxan, an alpha2-adrenoceptor antagonist, but not by R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzaz epine hydrochloride (SCH-23390), a dopamine D1 receptor antagonist. Furthermore, the contractions were inhibited in a dose-dependent manner by R(+)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride (SKF-38393) and (+/-)-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-be nzazepine hydrobromide (SKF-82958), dopamine D1 receptor agonists, and the inhibition was antagonized by both SCH-23390 and idazoxan, but not by spiperone, a dopamine D2 receptor antagonist. The results suggest that dopamine D1 receptors are located on the sympathetic nerve endings of guinea-pig vas deferens.
