BARORECEPTOR CONTROL OF VASOPRESSIN-PRODUCING CELLS IN STREPTOZOTOCIN-DIABETIC RATS

Electrical activities of the vasopressin (AVP)-producing cell in the supraoptic nucleus of the streptozotocin diabetic (STZ-DM) rat were recorded extracellularly and compared with those in the control rat. Higher hematocrit (45.3 +/- 0.5%, mean +/- SE) and lower mean blood pressure (MBP) (89.5 +/- 2.1 mmHg) suggested that STZ-DM rats were hypovolemic and hypotensive. The mean discharge rates of AVP cells were 15.2 +/- 3.1 Hz (STZ-DM) (p < 0.05 vs. control) and 8.8 +/- 0.8 Hz (control), respectively. Pressor and depressor responses were caused by phenylephrine (1.5 and 2.9 mug/kg, IV) and nitroprusside (1.5 mug/kg, IV), respectively, during the recording the AVP cells. Pressor and depressor responses lineally (STZ-DM; gamma = -0.7071, control; gamma = -0.9262) decreased and increased the discharge activity of the cells in both experimental groups, respectively. The MBP-neuronal activity relationship in STZ-DM did not differ statistically from that in the control. These results suggest that cardiovascular regulation of AVP release is well retained in STZ-DM rats.