Investigations into the pharmacological effects of spongiatriol

Acute intraperitoneal doses of spongiatriol, a compound extracted from marine sponges, caused blood pressure but not heart rate to fall in conscious hypertensive rats in a dose-dependent manner up to 50 mg/kg at which dose mean blood pressure fell 24%. Diarrhoea also resulted. Chronic oral doses (50 mg/kg every 3 h) lowered blood pressure by 73 mmHg after 48 h in conscious hypertensive rats and caused severe diarrhoea. Spongiatriol was an atrial stimulant in vitro and this effect could be greatly reduced by prior reserpinization or by beta-adrenoceptor blockade. In anaesthetized cats spongiatriol (50 mg/kg i.p.) caused reductions in blood pressure (19%), heart rate (11%) and cardiac output (12%). Spongiatriol 10(-5) g/ml had no effect on the response to noradrenaline in isolated rat tail arteries, markedly inhibited the response of in vitro guinea-pig ilea to acetylcholine and had a slight potentiating effect on the response of in vitro rat fundus stomach to serotonin and prostaglandin E2.