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

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 mediate by an increase in sympathetic activity as it was counteracted by alpha-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 less than 0.05), S-T segment changes, increases in heart rate (60 +/- 10, P less than 0.05) and arterial blood pressure (88 +/- 20, P less than 0.05) and ventricular tachyarrhythmias. All of these effects were prevented by pretreating animals with the alpha-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 alpha-adrenoceptors on coronary vessels.