Increase in coronary vascular resistance produced by stimulating neurons in the region of the area postrema of the cat

Abstract

Recently, Somberg, in a preliminary report (1983), noted that electrical stimulation of the area postrema causes an increase in coronary vascular resistance. The increase in resistance was mediated by an increase in sympathetic activity as it was counteracted by α-adrenergic receptor blockade. The purpose of our study was to confirm the findings of Somberg by using the method of chemical-induced activation of cell bodies in the area postrema. This was done by bilateral topical application of kainic acid to the area postrema of cats while monitoring coronary blood flow, heart rate, arterial blood pressure and the ECG. Topical application of kainic acid produced an increase in coronary vascular resistance (43 ± 13%, P < 0.05), S-T segment changes, increases in heart rate (60 ± 10, P < 0.05) and arterial blood pressure (88 ± 20, P < 0.05) and ventricular tachyarrhythmias. All of these effects were prevented by pretreating animals with the α-adrenoceptor blocking agent, phentolamine. These results suggest that chemical excitation of area postrema neurons produces coronary constriction that is mediated by the sympathetic nervous system and α-adrenoceptors on coronary vessels.