Abstract Intracerebroventricular (i.c.v.) injection of the 1,4-dihydropyridine (DHP) calcium channel agonist, Bay K8644 (30 μg/kg) increased mean blood pressure and the K +-evoked release of [ 3H]acetylcholine ([ 3H]ACh) from hippocampal slices in spontaneously hypertensive rats (SHR). The Bay K8644-induced hypertension was inhibited by a pretreatment with methylatropine (80 μg/kg, i.c.v.). In SHR, nicardipine, a DHP calcium channel antagonist, reduced mean blood pressure when i.c.v. injected (10 μg/kg). The nicardipine-induced hypotension was reduced by a pretreatment with hemicholinium-3 (20 μg, i.c.v.). Nicardipine (1 μM) did not modify, in SHR, the K +-evoked release of [ 3H]ACh, but inhibited the Bay K8644-induced increase in the ACh release. In normotensive rats, neither Bay K8644 nor nicardipine modify blood pressure, when centrally injected, or the stimulated release of [ 3H]ACh from hippocampal slices. The participation of central DHP sites in the cholinergic transmission in genetic hypertension is discussed.