LONG-DURATION PRESSOR-RESPONSES FOLLOWING ACTIVATION OF SUBFORNICAL ORGAN NEURONS IN RATS ARE THE RESULT OF INCREASED CIRCULATING VASOPRESSIN

Electrical stimulation in the subfornical organ (SFO) of male Sprague- Dawley rats resulted in biphasic increases in blood pressure (BP) with out a change in heart rate. The initial short duration (0-10 s) increa se in BP lasted throughout the 10 s stimulation period (area under the curve (AUC)= 104.3 +/- 15.26 mmHg/s, (mean +/- SEM) P < 0.001). Upon termination of the electrical stimulus, the BP remained elevated for a pproximately 55 s (long duration response, AUC = 327.5 +/- 48.22 mmHg/ s, P < 0.001). This long duration BP response was determined to be the result of an increase in circulating vasopressin (VP) as administrati on of a V-1 receptor antagonist abolished this response (AUC = -210.7 +/- 42.38 mmHg/s, P < 0.01). The results of the present study demonstr ate that the long duration component of the biphasic increase in BP ob served on response to electrical stimulation of the SFO is the result of increased concentrations of circulating VP. (C) 1997 Elsevier Scien ce Ireland Ltd.