Daily Drinking Patterns and Plasma Angiotensin II in the Budgerigar (Melopsittacus undulatus) and the Japanese quail (Coturnix coturnix japonica)

Abstract

Daily drinking patterns of budgerigars (Melopsittacus undulatus) fed millet grain were studied. Further, they were tested to determine whether exogenous angiotensin I, II and III (AI, AII and AIII) induce drinking and whether plasma AII is physiologically involved in natural drinking behavior. Japanese quail, given the same food as the budgerigars, were also studied, by way of comparison. (1) Budgerigars drank a slightly more water shortly after beginning of the artificially illuminated day period at 07:00 than during the following few hours. A peak of drinking was reached at one hour before or after the light was turned off at 19:00. They drank during dark periods, with illumination of less than 0.1 lux. (2) Japanese quail reached a peak of drinking activity one hour (07:00 to 08:00) after the start of the artificial day period. Thereafter, drinking activity decreased, but it increased again from 14:00, toward the beginning of the dark period. They did not drink water during the dark period. (3) The budgerigars responded to i. p. injection of AII by drinking in a similar manner to the Japanese quail. In budgerigars, injection of AIII stimulated either negligible drinking, or did not stimulate any drinking. AI induced drinking and SQ14225 (Captopril, an angiotensin-converting enzyme inhibitor) inhibited AI-induced drinking in budgerigars. (4) There was no significant correlation between the water intake and the plasma AII concentration in budgerigars. High doses of SQ14225 had either no or only slight effects on drinking activity in budgerigars, but clearly inhibited drinking in Japanese quail. (5) It may be concluded that variations in budgerigar plasma AII are probably not involved in or correlated with mechanisms inducing natural drinking, but in the Japanese quail plasma AII is associated with the physiological mechanisms of natural drinking.