Junnarkar A Y, Singh P P
Dept. of Pharmacology, IDPL Research Centre, Hyderabad, India.
Pharmacol Res Commun. 1988 Jun;20(6):451-63. doi: 10.1016/s0031-6989(88)80074-2.
The involvement of receptor subtypes in clonidine-induced hypothermia in electrically stimulated mice was studied using various alpha-adrenoceptor antagonists. Yohimbine, the selective alpha 2-adrenoceptor antagonist significantly blocked the action of low dose (50 micrograms/kg i.p.) of clonidine pretreated with Minimal Threshold Shock (12 mA, 0.2 Sec), while prazosin, selective alpha 1-adrenoceptor antagonist partially blocked the action, suggesting predominant involvement of alpha 2 and partial involvement of alpha 1-adrenoceptors. Under similar conditions when clonidine was used in higher dose (500 micrograms/kg i.p.), its action was blocked by prazosin, phenoxybenzamine and yohimbine suggesting involvement of both alpha 1 and alpha 2-adrenoceptors. In case of animals pretreated with Maximal Threshold Shock (36 mA, 0.2 Sec) the hypothermic action of clonidine in lower dose was blocked by all the three antagonists viz. prazosin, phenoxybenzamine and yohimbine, suggesting involvement of both alpha 1 and alpha 2-adrenoceptors, however, when clonidine was used in the higher dose, the action was significantly antagonised by prazosin and partially by yohimbine, suggesting predominant involvement of alpha 1 and partial involvement of alpha 2-adrenoceptors.
利用多种α-肾上腺素能受体拮抗剂，研究了受体亚型在电刺激小鼠中可乐定诱导体温过低现象中的作用。育亨宾，一种选择性α2-肾上腺素能受体拮抗剂，能显著阻断经最小阈值电击（12毫安，0.2秒）预处理的低剂量（50微克/千克腹腔注射）可乐定的作用，而哌唑嗪，一种选择性α1-肾上腺素能受体拮抗剂只能部分阻断其作用，这表明主要是α2-肾上腺素能受体起作用，α1-肾上腺素能受体也有部分参与。在类似条件下，当使用高剂量（500微克/千克腹腔注射）可乐定时，其作用被哌唑嗪、酚苄明和育亨宾阻断，这表明α1和α2-肾上腺素能受体都参与其中。在用最大阈值电击（36毫安，0.2秒）预处理的动物中，低剂量可乐定的降温作用被三种拮抗剂即哌唑嗪、酚苄明和育亨宾阻断，这表明α1和α2-肾上腺素能受体都参与其中；然而，当使用高剂量可乐定时，其作用被哌唑嗪显著拮抗，被育亨宾部分拮抗，这表明主要是α1-肾上腺素能受体起作用，α2-肾上腺素能受体也有部分参与。
