Oriowo M A
Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait.
J Pharm Pharmacol. 1995 Aug;47(8):661-4. doi: 10.1111/j.2042-7158.1995.tb05855.x.
In field-stimulated rat vas deferens, clonidine (10(-9)-10(-7) M) and alpha-methylnoradrenaline (10(-7)-3 x 10(-5) M) concentration-dependently inhibited twitch response to electrical field stimulation. The inhibitory effects of clonidine and alpha-methylnoradrenaline were similarly reduced by phenoxybenzamine (10(-6) M). However, idazoxan (3 x 10(-7) M) antagonized clonidine but not alpha-methylnoradrenaline-induced responses. The inhibitory effect of alpha-methylnoradrenaline was also not antagonized by phentolamine (3 x 10(-7) M), SK&F 104856 (2-vinyl-7-chloro-3,4,5,6-tetrahydro-4-methylthienol[4,3,2 ef][3]benzazepine) 3 x 10(-6) M) or yohimbine 3 x 10(-7) M). These antagonists however, attenuated the twitch-inhibiting effect of clonidine. The -logKB values were 8.02 +/- 0.05, 6.91 +/- 0.10, and 7.58 +/- 0.07 for phentolamine, SK&F 104856 and yohimbine respectively. In-vivo treatment of rats with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (6 mg kg-1), to inactivate prejunctional alpha 2-adrenoceptors, attenuated clonidine, but not alpha-methylnoradrenaline-induced responses. It was concluded that adrenoceptors are not involved in the prejunctional inhibitory effects of alpha-methylnoradrenaline in the rat vas deferens.
在电场刺激的大鼠输精管中，可乐定（10⁻⁹ - 10⁻⁷ M）和α-甲基去甲肾上腺素（10⁻⁷ - 3×10⁻⁵ M）对电场刺激引起的抽搐反应呈浓度依赖性抑制。酚苄明（10⁻⁶ M）同样降低了可乐定和α-甲基去甲肾上腺素的抑制作用。然而，咪唑克生（3×10⁻⁷ M）拮抗可乐定诱导的反应，但不拮抗α-甲基去甲肾上腺素诱导的反应。酚妥拉明（3×10⁻⁷ M）、SK&F 104856（2-乙烯基-7-氯-3,4,5,6-四氢-4-甲基噻吩并[4,3,2 ef][3]苯并氮杂卓）3×10⁻⁶ M）或育亨宾3×10⁻⁷ M）也不拮抗α-甲基去甲肾上腺素的抑制作用。然而，这些拮抗剂减弱了可乐定的抽搐抑制作用。酚妥拉明、SK&F 104856和育亨宾的-logKB值分别为8.02±0.05、6.91±0.10和7.58±0.07。用N-乙氧羰基-2-乙氧基-1,2-二氢喹啉（6 mg kg⁻¹）对大鼠进行体内处理以灭活突触前α₂-肾上腺素能受体，减弱了可乐定诱导的反应，但不减弱α-甲基去甲肾上腺素诱导的反应。得出的结论是，肾上腺素能受体不参与α-甲基去甲肾上腺素对大鼠输精管的突触前抑制作用。
