Central integrating mechanism of the Bezold-Jarisch and baroceptor reflexes.

LEE, T. M., J. S. Kuo, AND C. Y. CHAI. Central integrating mechanism of the Besold-Jarisch and baroceptor reflexes. Am. J. Physiol. 222 (3) : 713-720. 1972.-The central integrating mechanism of the Bezold-Jarisch (intracardiac veratrine) and baroceptor (intravenous epinephrine) reflexes was studied in cats under chloralose and urethan. It was found that midcollicular decerebration and lower pontine transection did not affect the reflexes, but electrolysis of the nucleus solitarius abolished both reflexes. Electrolysis of the dorsal midline area only moderately shortened the duration but not the intensity of both reflexes. Electrolysis of the ventral midline area abolished the bradycardia induced by baroceptor reflex. Electrolysis of the dorsal motor nucleus of the vagus and ambiguus nucleus abolished only the bradycardic effect of both reflexes. Ethybenztropine, 0.1 mg, but not bretylium, 0.6 mg, or INPEA (N-isopropyl-p-nitrophenylethanolamine), 0.9 mg, administered into the fourth cerebroventricle, abolished both reflexes. Data suggest that the above nuclei of the medulla oblongata are important for the integration of the bradycardic effect of the Bezold-Jarisch and baroceptor reflexes, and that the ventral midline area is important for the baroceptor reflex. At least one cholinergic synapse is involved in the integrating mechanism.