Hypotensive effect of ocoteine

Ocoteine is an alkaloid isolated from Thalictrum isopyroides. In anaesthetized normotensive rats, conscious normotensive arts and renal hypertensive rats, ocoteine 1-10 mg'/kg administered intravenously caused an acute, long lasting and dose-dependent decrease in systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and mean arterial pressure (MAP). ?The hypotensive effect of ccoteine is more pronounced on DAP than on SAP. Ocoteine 0.2mg/kg injected intracerebro ventricularly has also hypotensive effect. The hypotcusive effect was not abolished after bilateral vagotcmy and intravenous pretrcatment with atropine, and after intravenous pretreatment with diphenhydra mine. In. the pithed rats ocoteine 1-3 mg/kginjected iv 15 min previously shifted the log dose-pressor response curves of α1-ad renoceptor agonist methoxamine to the right in parallel manner, but Ms no significant effect on the log dose-pressor response curve of B-HT 920, a highly selective α2-adrenocep tor stimulating agent. The results obtained suggest that ocoteine selectively blocks the vascular postsynaptic α1-adrenoceptors. Ocoteine may also possess central hypotensive effect. The hypotensive effect of ocoteine is not related to the activation of vagus and to the release of histamine.