The dipsogen angiotensin II does not stimulate ethanol intake in mice

Abstract

Mice that were habituated to drinking ethanol solution and mice that had drunk water only (naive mice) were given an ICV infusion of angiotensin II (Ang II) at 2.9 ng/h for 8 days to determine the effect of chronic ethanol intake on the ingestive response to this potent dipsogen. Ang II infusion in alcohol-naive mice increased daily water intake from 3.7 ± 0.2 ml ( mean ± SE, n = 6) to 11.0 ± 1.5 ml on day 4 ( p < 0.001) and to 18.3 ± 2.6 ml on day 8 ( p < 0.001). In subsequent experiments, mice had access to 4% ethanol solution up to day 4 and then to water for 4 days during the Ang II infusion. Alcohol-naive mice did not increase daily fluid intake until the water was provided on day 5; intake increased to 17.5 ± 2.3 ml on day 8 ( p < 0.001, n = 7). Mice accustomed to drinking 4% ethanol (4.3 ± 0.3 ml/day) also did not increase intake until the water was provided; intake reached 22.9 ± 3.0 ml of water on day 8 ( p < 0.001, n = 7). Mice accustomed to drinking 10% ethanol behaved similarly ( n = 4). Thus, alcohol-naive or -habituated mice did not respond to this dipsogenic stimulus until water was available; the thirst for water was unimpaired. Preference-aversion tests showed that mice drank little or no 4% ethanol (or even 2% ethanol) when water was also available. Taste aversion, plus previous experience from ingestion of ethanol in habituated mice, may explain the rejection of ethanol to quench Ang II-induced thirst. Experimental results obtained using other aversive solutions, 3 mM quinine and 300 m M KCI, suggest that postingestional, metabolic effects of solutes may also contribute to such rejection.