Effect of administration of angiotensin II and isoproterenol, alone and in combination, on drinking and tail skin temperature of the rat.
Both angiotensin II (AII) and the beta-adrenergic agonist isoproterenol are well known to induce drinking and increase tail skin temperature (TSK) in rats. Previous studies have shown that these two compounds have an additive, rather than interactive, dipsogenic effect when administered together. The present studies confirmed the additivity of the dipsogenic effect of the two compounds and attempted to extend these results to TSK. The results reveal that at a series of dosage combinations of AII [100 and 125 micrograms/kg, subcutaneously (SC)] and isoproterenol (ISOP) (10, 12.5, and 25 micrograms/kg, SC) administered together, the increase in TSK usually induced by each compound was canceled. This occurred at the lower doses of ISOP in combination with AII. Thus, the differences between dipsogenic and thermoregulatory effects of combined doses of AII and ISOP suggest a difference in central integration. Important differences between the thermoregulatory responses to administration of the two compounds include increases in metabolic rate and colonic temperature when ISOP is administered and decreases in both when AII is administered. It is suggested that the effect of the two compounds to cancel each other with respect to TSK is related to their opposite effects on metabolic rate.
Fregly
M J
MJ
Department of Physiology, College of Medicine, University of Florida, Gainesville 32610, USA.
Rowland
N E
NE
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D004326:Drinking / Q000187:drug effects*; D004347:Drug Interactions; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012881:Skin Temperature / Q000187:drug effects*; D013623:Tail / Q000502:physiology
D000804:Angiotensin II; D007545:Isoproterenol