Central autonomic modulation of cardiac baroreflex by corticotropin-releasing factor

The effects of intracerebroventricular administration of corticotropin-releasing factor (CRF) on baroreflex control of heart rate were studied in conscious, unrestrained rats. Stimulus-response curves relating mean arterial pressure (MAP) to pulse interval were constructed for assessment of baroreflex function. CRF, intracerebroventricularly injected, elicited dose-related reductions of resting pulse interval, response range, and reflex gain and elevations of resting arterial pressure and MAP50 (arterial pressure at midrange). Earlier peripheral blockade of cardiac vagal influences with atropine methyl nitrate greatly attenuated the effects of CRF on resting pulse interval, response range, and reflex gain. In contrast, earlier blockade of cardiac sympathetic influences with intravenous propranolol treatment did not alter the ability of CRF to reduce resting pulse interval, response range, and reflex gain. The central nervous system effects of CRF on cardiac baroreflex function were qualitatively similar to the actions of atropine methyl nitrate. It is concluded that CRF alters transmission in central nervous system pathways mediating baroreceptor-induced activation of cardiac vagal motor neurons.