Morris J L
Centre for Neuroscience and Department of Anatomy and Histology, School of Medicine, Flinders University of South Australia, Adelaide, South Australia 5001, Australia.
Am J Physiol. 1999 Jul;277(1):H58-64. doi: 10.1152/ajpheart.1999.277.1.H58.
This study has characterized constrictions of small cutaneous arteries in the guinea pig ear in response to electrical stimulation of the cervical sympathetic nerve (SNS) in vivo. Video microscopy and on-line image analysis were used to examine diameter changes of ear arteries (80-140 micrometers resting diameter) in anesthetized guinea pigs. Trains of 50-300 impulses, but not single pulses or short trains, produced frequency-dependent (2-20 Hz) constrictions. The purinoceptor antagonist suramin (30 microM) greatly reduced constrictions produced by exogenous ATP but did not affect constrictions produced by SNS at 10 Hz or exogenous norepinephrine. The alpha(2)-adrenoceptor antagonist yohimbine (1 microM) enhanced the peak amplitude of sympathetic constrictions at lower stimulation frequencies (1-5 Hz). The amplitude of constrictions to SNS at 10 Hz was reduced, and the latency of constrictions was increased by the alpha(1)-adrenoceptor antagonist prazosin (1 microM). Constrictions to SNS at 10 Hz remaining after prazosin treatment were reduced in amplitude by dihydroergotamine (2 microM) and were attenuated further by the neuropeptide Y Y(1)-receptor antagonist 1229U91 (0.3 microM). Thus norepinephrine and neuropeptide Y act as cotransmitters to mediate sympathetic constriction of small ear arteries at higher stimulation frequencies (10 Hz), but ATP does not seem to contribute directly to these constrictions.
本研究描述了豚鼠耳部小皮动脉在体内对颈交感神经（SNS）电刺激的收缩反应。采用视频显微镜和在线图像分析技术，检测麻醉豚鼠耳部动脉（静息直径80 - 140微米）的直径变化。50 - 300次脉冲串可引起频率依赖性（2 - 20赫兹）收缩，而单个脉冲或短脉冲串则无此效应。嘌呤受体拮抗剂苏拉明（30微摩尔）可显著减弱外源性ATP引起的收缩，但不影响10赫兹时SNS引起的收缩或外源性去甲肾上腺素引起的收缩。α₂肾上腺素能受体拮抗剂育亨宾（1微摩尔）可增强较低刺激频率（1 - 5赫兹）时交感神经收缩的峰值幅度。α₁肾上腺素能受体拮抗剂哌唑嗪（1微摩尔）可降低10赫兹时对SNS收缩的幅度，并延长收缩的潜伏期。哌唑嗪处理后，10赫兹时对SNS的收缩在幅度上被双氢麦角胺（2微摩尔）降低，并被神经肽Y Y₁受体拮抗剂1229U91（0.3微摩尔）进一步减弱。因此，去甲肾上腺素和神经肽Y作为共递质，在较高刺激频率（10赫兹）时介导耳部小动脉的交感神经收缩，但ATP似乎并不直接参与这些收缩。
