ANTIHYPERTENSIVE EFFECTS OF DL-TETRAHYDROPALMATINE - AN ACTIVE PRINCIPLE ISOLATED FROM CORYDALIS

1. The effects of DL-tetrahydropalmatine (DL-THP) on cardiovascular fu nction and hypothalamic release of monoamines were assessed in rats un der urethane anaesthesia. 2. Intravenous administration of DL-THP (1-1 0 mg/kg) produced hypotension, bradycardia, a decrease in hypothalamic serotonin and noradrenaline release and an increase in hypothalamic d opamine release in rats. 3. Intrahypothalamic administration of DOI (a serotonergic 5-HT2 receptor antagonist) or apomorphine (a dopamine D- 2-receptor agonist) produced the opposite effects and reversed DL-THP- induced hypotension and bradycardia. 4. The data suggest that DL-THP a cts through the 5-HT2 and/or D-2-receptor antagonism in the hypothalam us to induce hypotension and bradycardia in rats.