Byrne N G, Hirst G D, Large W A
Br J Pharmacol. 1985 Sep;86(1):217-27. doi: 10.1111/j.1476-5381.1985.tb09452.x.
The nature of adrenoceptors in basilar arteries of neonatal rats was investigated by means of electrophysiological techniques. In immature (2-6 day postnatal) rats, micro-injection of noradrenaline elicited a depolarization which consisted of two components. The initial 'fast' component (time to peak of 0.3-4s) was slightly reduced by phentolamine and was not antagonized by propranolol. The second 'slow' component (time to peak of about 50s) was not blocked by phentolamine but was antagonized by low concentrations (10(-7) M) of propranolol. In immature rats, micro-injection of isoprenaline was more potent than noradrenaline in evoking the 'slow' depolarization but less effective in eliciting the 'fast' response. The pharmacology with respect to adrenoceptor antagonists of both components of the isoprenaline- and noradrenaline-induced depolarizations was similar. There was some evidence of inhibitory beta-adrenoceptors in immature rat basilar vessels. In adult rats (6 week old) noradrenaline produced a large 'fast' depolarization which was followed by a 'slow' tail response. Both components were not antagonized by phentolamine or propranolol. It appears that in the basilar artery of neonatal rats there are excitatory alpha- and inhibitory beta-adrenoceptors but the major responses to noradrenaline and isoprenaline are mediated by gamma- and excitatory beta-receptors. In adult animals the gamma-adrenoceptor predominates. Experiments were carried out in which agonists were applied by ionophoresis. These results confirm the presence of excitatory beta-receptors in neonatal basilar vessels and show the response has slow kinetics and it is likely that the beta-receptors are distributed uniformly over the smooth muscle surface. In adult animals it was not possible to elicit an excitatory beta-receptor-mediated response. The ionophoretic application of noradrenaline never evoked a perceptible depolarization which could be attributed to gamma-adrenoceptor stimulation. This result is discussed in terms of receptor distribution with respect to synaptic function in a syncytium.
采用电生理技术研究新生大鼠基底动脉肾上腺素能受体的性质。在未成熟（出生后2 - 6天）大鼠中，微量注射去甲肾上腺素可引发去极化，该去极化由两个成分组成。最初的“快速”成分（达到峰值的时间为0.3 - 4秒）可被酚妥拉明轻微减弱，且不被普萘洛尔拮抗。第二个“缓慢”成分（达到峰值的时间约为50秒）不被酚妥拉明阻断，但可被低浓度（10⁻⁷M）的普萘洛尔拮抗。在未成熟大鼠中，微量注射异丙肾上腺素在引发“缓慢”去极化方面比去甲肾上腺素更有效，但在引发“快速”反应方面效果较差。异丙肾上腺素和去甲肾上腺素诱导的去极化的两个成分关于肾上腺素能受体拮抗剂的药理学性质相似。有证据表明未成熟大鼠基底血管中存在抑制性β - 肾上腺素能受体。在成年大鼠（6周龄）中，去甲肾上腺素产生一个大的“快速”去极化，随后是一个“缓慢”的尾部反应。这两个成分均不被酚妥拉明或普萘洛尔拮抗。似乎在新生大鼠的基底动脉中存在兴奋性α - 和抑制性β - 肾上腺素能受体，但对去甲肾上腺素和异丙肾上腺素的主要反应是由γ - 和兴奋性β - 受体介导的。在成年动物中，γ - 肾上腺素能受体占主导。进行了通过离子电泳施加激动剂的实验。这些结果证实了新生基底血管中存在兴奋性β - 受体，并表明该反应具有缓慢的动力学，且β - 受体可能均匀分布于平滑肌表面。在成年动物中，无法引发兴奋性β - 受体介导的反应。离子电泳施加去甲肾上腺素从未引发可归因于γ - 肾上腺素能受体刺激的可察觉的去极化。根据在合胞体中关于突触功能的受体分布对该结果进行了讨论。
