Water and salt intake of wild rabbits (Oryctolagus cuniculus (L)) following dipsogenic stimuli.

Abstract

SUMMARY1. Wild rabbits trapped in their natural habitat and adapted to laboratory conditions were studied. Food, water and electrolyte (0-5 M-NaCl, 0-5 M-KCl, 0-25 M-MgCl2 and 0-25 M-CaCl2) consumption, urinary volume and sodium losses were monitored daily following stimuli which were found dipsogenic in other species.2. Water drinking was observed immediately after the intravenous injection of 1 M-NaCl (3 ml/kg), and following withdrawal of a mean of 13-9 % of calculated blood volume. Daily intake of water decreased during intracerebroventricular (i.c.v.) infusion of 0 3 M-NaCl in artificial cerebrospinal fuid (c.s.f.), during i.c.v. infusion of 0 9 M-mannitol c.s.f., both at a rate of 17 1d/h, following peritoneal dialysis with 5 % (w/v) glucose solution, and during food restriction. Water intake was not affected following intravenous administration of acetazolamide (10 mg/kg).3. Daily intake of 0'5 M-NaCl solution was increased following peritoneal dialysis with 5 % (w/v) glucose solution, which caused hyponatraemia, but not after haemorrhage which caused about the same sodium deficit as peritoneal dialysis, but as an isosmotic loss. 4. Administration of two different angiotensin II analogues, systemically or i.c.v., failed to induce water drinking. However, urinary sodium excretion and intake of 05 M-NaCl were increased during the 5 days of i.c.v. infusion of angiotensin II (10 pmol/h). Infusion for 1 day of angiotensin II (500 pmol/h) led to increased urinary sodium excretion which was followed by increased intake.5. The intake of other electrolyte solutions was not significantly affected by any of the treatments detailed above.6. The mechanisms participating in initiation of thirst in wild rabbits are very sensitive to decrease in blood volume, in contrast to other species studied in laboratories. Angiotensin II at the doses and routes administered was not dipsogenic in wild rabbits.7. The increased intake of 05 M-NaCl solution observed during and after the long-term intraventricular administration of angiotensin II in the wild rabbit appears predominantly a response to sodium deficit caused by natriuresis. The persistence of appetite after the cessation of infusion is indicative of a residual effect on central mechanisms of salt appetite.

Amifostine is a Potent Radioprotector of Salivary Glands in Radioiodine Therapy

“…It is well known that rabbits can manage for long periods without drinking water [16,56], suggesting potential differences in the se-cretion efficiency of their salivary glands and throwing a different light on our results, the upshot being that it is unknown whether this animal trial can be applied to humans in the same way. At any rate, initial results obtained by Bohuslavizki et al [11] reveal that amifostine seems to have similar protective effects on the human salivary glands.…”

Angiotensin, Thirst, and Sodium Appetite

“…and that infusion of ANG II or III into the lateral ventricle causes delayed increases in daily water intake (169, 170, 1. Intracranial administration 681) should be contrasted with other experiments on wild and New Zealand rabbits (125,168,598,599), in which no In mongrel dogs, intracranial injection of 1-5,000 pmol ANG II caused vigorous, short-latency, dose-depen-effect of intracranial ANG II on water intake could be demonstrated. However, after several days of infusion dent drinking, largely completed within 15 min of injection and producing water intakes exceeding 400 ml by 1 h after into the lateral ventricle, NaCl intake was increased (598), and experiments with an ACE inhibitor also suggest that the highest dose injected into the most sensitive sites (183,194,463).…”

Human Salt Taste and the Lingual Surface Potential Correlate

“…We also speculate that the human ability to discriminate salt concentrations may not be essential for survival in modern society because salt is ever present. However, in the wild, salt is not always available and animals unable to detect salt are at survival disadvantage (Jacobs 1978;Denton et al 1985). Presumably, a similar disadvantage would occur to humans who are not adept at tasting salt and who exist in a setting in which salt is not freely available.…”