| Abstract: | Intravertebral artery injection of yohimbine at total doses of 10, 50, 100 and 200 micrograms caused dose-related enhancement of the systemic pressor response to bilateral carotid artery occlusion (BCO) in dogs; the response was depressed by 5000 micrograms yohimbine. Basal blood pressure was increased by 100 and 200 micrograms yohimbine, and decreased by 5000 micrograms. Intravertebral artery injection of rauwolscine, 5 micrograms enhanced the BCO response but had no effect on basal blood pressure. Corynanthine, 200 or 500 micrograms was ineffective. The pressor response to intravenously administered noradrenaline was not affected by any of the drugs. It is concluded that enhancement of the BCO response by yohimbine and rauwolscine is caused by blockade of central alpha 2-adrenoceptors. |
