Hypotensive and vasodilator actions of SK&F 24260, a new dihydropyridine derivative.

1 The blood pressure of conscious normotensive, Goldblatt-hypertensive and genetic-hypertensive rats and normotensive dogs was lowered by SK&F 24260 (1,4-dihydro-2,6-dimethyl-4-(2-trifluormethylphenyl)-3,5-pyridinedicarboxylic acid diethyl ester).2 Tachycardia always accompanied the hypotension. In rats propranolol abolished the tachycardia but in dogs there was only a small reduction in the heart rate response.3 In conscious dogs there was an increase in left ventricular output and a marked fall in total peripheral resistance.4 SK&F 24260 dilated resistance vessels in rat hindquarters. Dilatation was caused by doses of SK&F 24260 some 50 times smaller than those of hydrallazine.5 In preparations of cat skeletal muscle and intestinal vascular beds SK&F 24260 selectively dilated resistance vessels in preference to capacitance vessels and resembled hydrallazine rather than papaverine which has no such selectivity.6 Pre-capillary sphincter vessels were also dilated by SK&F 24260. Changes in fluid equilibrium caused by SK&F 24260 were consistent with selective dilatation of resistance vessels.