Wong K K
Institute of Pharmacology, National Yang Ming Medical College, Taipei, Taiwan, Republic of China.
Artery. 1993;20(4):180-8.
Clonidine was a partial agonist of adrenoceptors and the effects of a range of clonidine doses on the mean arterial pressure and heart rate of rats were evaluated. It was found that low doses of clonidine, 30-300 micrograms/kg, induced a significant hypotension whereas high doses of clonidine, 3-18 mg/kg, were unable to decrease the blood pressure significantly. The reversal by high doses of clonidine of the hypotension induced by low dose of clonidine was possibly due to the blood vessel contraction induced by a high dose of clonidine. On the other hand, both low and high doses of clonidine induced bradycardia in the in vivo as well as in vitro studies.
可乐定是肾上腺素能受体的部分激动剂，评估了一系列可乐定剂量对大鼠平均动脉压和心率的影响。结果发现，低剂量的可乐定（30 - 300微克/千克）可引起显著的低血压，而高剂量的可乐定（3 - 18毫克/千克）则不能显著降低血压。高剂量可乐定对低剂量可乐定所致低血压的逆转作用可能是由于高剂量可乐定引起的血管收缩。另一方面，在体内和体外研究中，低剂量和高剂量的可乐定均能引起心动过缓。
