THE SENSITIVITY OF THE BEZOLD-JARISCH REFLEX IS INCREASED IN RATS WITH SINOAORTIC DEAFFERENTATION

The sensitivity of the Bezold-Jarisch reflex was evaluated by the card iovascular changes in response to intravenous injection of increasing doses of serotonin (5-hydroxytryptamine) in conscious male Wistar (300 -350 g) rats 1 and 15 days after sinoaortic deafferentation. The brady cardia and hypotension induced by serotonin (2, 4, 8, 16 and 32 mu g, iv) were dose dependent in sinoaortic deafferentated as well as in sha m-operated rats, but the magnitude of the bradycardiac and depressor r esponse to all doses of serotonin was significantly greater in both gr oups of sinoaortic deafferentated rats [1 (N = 8) and 15 days (N = 8)] than in sham-operated animals [1 (N = 8) and 15 days (N = 8)], indica ting an increased sensitivity of the Bezold-Jarisch reflex. These data suggest that the increased sensitivity of the Bezold-Jarisch reflex m ay have some functional role in cardiovascular regulation after remova l of aortic and carotid baroreceptors.