Adebanjo A O, Ambache N
West Afr J Pharmacol Drug Res. 1979;5(1):95-105.
Isolated vas deferens preparations from 16 rabbits of the New Zealand white strain were subjected to electrical and chemical excitability under physiological conditions and under the influence of drugs. Such smooth muscle fibres were strictly confined to the terminal 3 cm. segments of the distal 'urethral' portions of the vasa deferentia. Intermittent field stimulation, at 60 second intervals, was provided by a stimulator of low output impedance under constant parameters of voltage, pulse width and frequency. Results from this investigation revealed the undermentioned anomalous but distinct findings viz: (a) the presence of a minor adrenergic component which disappeared in phentolamine but remained unaffected by prolonged exposures to phenoxybenzamine; (b) the presence of a predominantly non-adrenergic component which was totally refractory to phenoxybenzamine but suffered a weak diminution in phentolamine; and (c) the picture of a phentolamine-insensitive but twitch-inhibiting effect shared by both tyramine and noradrenaline. Rabbit vasa consistently displayed a remarkable insensitivity to the motor effects of submicromolar concentrations of the putative neurotransmitter substance i.e. noradrenaline. The indirect sympathomimetic agent, tyramine failed to elicit any contractions when employed in doses as massive as 290 micrometers. i.e. 5 x 10(-5) g/ml, except in 2 out of 14 trials when a weak phentolamine-susceptible bursts of single contractions were produced. Thus, the adrenoceptors involved in the mediation of the twitch-inhibiting effects, appear not to behave towards conventional adrenoceptor antagonists in the classified manner. It seems appropriate therefore to invoke an unknown neurotransmitter for the non-adrenergic component in this motor transmission.
对16只新西兰白兔品系的离体输精管标本在生理条件下以及药物影响下进行电兴奋性和化学兴奋性实验。此类平滑肌纤维严格局限于输精管远侧“尿道”部分的末端3厘米节段。由一台低输出阻抗刺激器在电压、脉冲宽度和频率恒定参数下，每隔60秒进行间歇性场刺激。本研究结果揭示了下述异常但明显的发现，即：(a) 存在一个较小的肾上腺素能成分，它在酚妥拉明作用下消失，但长时间暴露于酚苄明时不受影响；(b) 存在一个主要的非肾上腺素能成分，它对酚苄明完全无反应，但在酚妥拉明作用下稍有减弱；以及(c) 酪胺和去甲肾上腺素都具有对酚妥拉明不敏感但抑制抽搐的效应。兔输精管对亚微摩尔浓度的假定神经递质即去甲肾上腺素的运动效应始终表现出显著的不敏感性。间接拟交感神经药酪胺在剂量高达290微摩尔即5×10(-5)克/毫升时，除了在14次试验中的2次产生了对酚妥拉明敏感的微弱单次收缩爆发外，未能引发任何收缩。因此，参与介导抑制抽搐效应的肾上腺素能受体，似乎并不以分类方式对传统肾上腺素能受体拮抗剂起反应。所以，在此运动传递中为非肾上腺素能成分援引一种未知神经递质似乎是合适的。
