Enhancement of osmotic thirst elicited by electric stimulation of the limbic system in dogs.
Seven dogs were chronically implanted with 30 electrodes directed at various structures of the basal forebrain. Osmotic thirst threshold (expressed as an increase in plasma osmolality and a decrease in cellular water content caused by an intravenous infusion of 5% NaCl, necessary to induce drinking) was measured during electric stimulation of the basal forebrain and compared to that found under control conditions. Stimulation through 11 electrodes located in the lateral part of the septum (5 locations) and other parts of the limbic system markedly decreased the osmotic thirst threshold. The increment in plasma osmolality necessary to elicit drinking decreased from 9.7 +/- 1.3 to 4.8 +/- 1.2 mmol/kg (n = 11). The volume of water drunk at the thirst threshold did not differ significantly. A significant augmentation of the volume of water drunk during 1 h following infusion of hypertonic saline was observed when the infusion was combined with stimulation of the gyrus rectus, precommissural septum and nucleus accumbens. These and previous results (SZCZEPANSKA-SADOWSKA et al., 1979) suggest that the limbic system of the basal forebrain exerts both excitatory and inhibitory influences on the thirst system. The prolonged poststimulatory overdrinking indicates that enhancement of osmotic thirst cannot be entirely explained by an immediate action of the stimulating current on the neurons of the thirst system.
D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D008032:Limbic System / Q000502:physiology*; D008297:Male; D009994:Osmolar Concentration; D013894:Thirst / Q000502:physiology*