Involvement of central alpha- and beta-adrenoceptors in the pressor response to electrical stimulation of the rostral ventrolateral medulla in rats.

1. Electrical stimulation of the C1 area of the rostral ventrolateral medulla in rats elicits an increase in mean arterial pressure (MAP). 2. This increase in MAP is attenuated by intra-hypothalamic and intracisternal administration of the non-selective beta-adrenoceptor antagonist (+/-)-propranolol and the beta 2-selective antagonist ICI 118551. 3. The selective beta 1-antagonist atenolol and (+)-propranolol, which is inactive on beta-adrenoceptors, did not alter the increase in MAP produced by stimulation of the C1 area. 4. The alpha 2-adrenoceptor antagonist idazoxan enhanced the effects of C1 stimulation on MAP when administered either into the posterior hypothalamus or intracisternally. 5. The results indicate that beta 2- and alpha 2-receptors both have a role in the mediation of the rise in MAP during stimulation of the C1 area and that the receptors involved are located both within the hypothalamus and the spinal cord.