Intracerebroventricular saccharide infusions inhibit thirst induced by systemic hypertonicity

The effect of intracerebroventricular (i.c.v.) infusion of various iso- and hypertonic saccharide solutions on water intake stimulated by intracarotid (i.c.) infusion of hypertonic NaCl was studied in sheep. Without an i.c.v. infusion, water intake during a 10-min period following an i.c. infusion of 4 M NaCl (1.4 ml/min over 20 min) was 1.5-2.0 litres. I.c.v. infusion of all saccharide solutions (made up in artificial cerebrospinal fluid (CSF) with no Na) tested, 0.27 or 0.7 M D-glucose, L-glucose, 2-deoxyglucose and sucrose, decreased (35-65%) water intake. In general, there was little or no difference in antidipsogenic effectiveness between the isotonic and the hypertonic solutions or between the different saccharides used. I.c.v. infusion of artificial CSF ([Na] = 150 mM) did not alter water intake. CSF [Na] was decreased by all of the saccharide infusions. CSF osmolality was increased by the hypertonic solutions, was decreased by the artificial CSF and was unchanged by the isotonic solutions infused. The observation that the antidipsogenic effectiveness of saccharides which readily cross the blood-brain barrier (BBB; D-glucose, 2-deoxyglucose) was similar to that of saccharides which do not readily cross the BBB (sucrose, L-glucose) contrasts with effects reported on sodium appetite and suggests that the Na sensors involved in the inhibition of hypertonic NaCl-stimulated water intake are located close to or on the surface of the brain ventricular system, i.e. are responsive to changes in CSF [Na].(ABSTRACT TRUNCATED AT 250 WORDS)