Ren L M, Hoyle C H, Burnstock G
Department of Anatomy and Developmental Biology and Centre for Neuroscience, University College London, UK.
Eur J Pharmacol. 1996 Dec 30;318(2-3):411-7. doi: 10.1016/s0014-2999(96)00791-1.
Contractile responses of the circular muscle of the isolated vas deferens to electrical stimulation (10-80 Hz) and to noradrenaline significantly decreased with increasing age in 3-week-, 10-week- and 18-month-old guinea pigs, observed by the cannula insertion method. There were no significant differences in the contractile responses induced by alpha,beta-methylene ATP or BaCl2 between 3 and 10 weeks old, but the responses to alpha,beta-methylene ATP or BaCl2 decreased in 18-month-old guinea pigs. The contractile response to electrical stimulation was monophasic in 3-week-old guinea pigs, a small portion of which remained after the treatment with prazosin. Desensitisation of P2X-purinoceptors with alpha,beta-methylene ATP significantly inhibited the contractile responses to stimulation with relatively low frequencies, and the combination of both prazosin and alpha,beta-methylene ATP abolished the stimulation-induced contractions. In 10-week- and 18-month-old guinea pigs electrical stimulation evoked a transient contraction followed by a second contraction at the offset of the stimulation (the after-response). The after-responses were blocked by prazosin. These results show that the dominant component of sympathetic cotransmission is noradrenaline; a purinergic component also exists in the sympathetic contraction in the circular muscle of the vas deferens in young guinea pigs, but is virtually absent in the later stages of development. The sympathetic contractions of the circular muscles significantly decrease with increasing age and this appears to be due to changes in postjunctional, rather than prejunctional, mechanisms.
采用插管法观察发现，在3周龄、10周龄和18月龄的豚鼠中，随着年龄增长，离体输精管环行肌对电刺激（10 - 80Hz）和去甲肾上腺素的收缩反应显著降低。3周龄和10周龄豚鼠对α,β-亚甲基ATP或BaCl₂诱导的收缩反应无显著差异，但18月龄豚鼠对α,β-亚甲基ATP或BaCl₂的反应降低。3周龄豚鼠对电刺激的收缩反应为单相，其中一小部分在用哌唑嗪处理后仍存在。用α,β-亚甲基ATP使P2X嘌呤受体脱敏可显著抑制对相对低频刺激的收缩反应，哌唑嗪和α,β-亚甲基ATP联合使用可消除刺激诱导的收缩。在10周龄和18月龄豚鼠中，电刺激诱发短暂收缩，随后在刺激结束时出现第二次收缩（后反应）。后反应被哌唑嗪阻断。这些结果表明，交感神经共同传递的主要成分是去甲肾上腺素；嘌呤能成分在幼年豚鼠输精管环行肌的交感收缩中也存在，但在发育后期几乎不存在。环行肌的交感收缩随着年龄增长而显著降低，这似乎是由于节后机制而非节前机制的变化所致。
