Effects of CSF ANG II and AVP on sweating in the heat-stressed patas monkey

Increasing cerebrospinal fluid [Na+] reduces sweat rate (msw) in the heat-stressed patas monkey (Erythrocebus patas). This study determined the potential role of two neuropeptides, angiotensin II (ANG II) and arginine vasopressin (AVP), in mediating this response. Artificial cerebrospinal fluid, containing either ANG II or AVP, was infused into the third cerebral ventricle of lenperone-tranquilized monkeys (n = 4) exposed to 41 +/- 2 degrees C. Solutions were infused at 16.5 microliters/min for 25 min (total vol approximately 413 microliters). ANG II (1.25, 2.5, 5, and 10 ng/microliters) tended to decrease .msw. However, during infusion, only the decline at 10 min associated with the 1.25-ng/microliters dose (26%) was different (P less than 0.004) from control. This dose elevated (P less than 0.004) core rectal temperature by 1.14 degrees C at 20 min postinfusion. In contrast, AVP (0.5 and 1.5 micrograms/microliters artificial cerebrospinal fluid) had no significant effect on .msw compared with control infusions. Both doses of AVP produced a slight but significant increase in rectal temperature of 0.14 and 0.22 degrees C, respectively, at 20 min postinfusion. In conclusion, the magnitude and time course of the change in .msw with central ANG II suggest that it does not act as the sole mediator of the decline in .msw observed with elevated cerebrospinal fluid [Na+]. The minimal effects produced by third ventricular AVP exclude this route as a means by which AVP could modulate .msw during dehydration.