Delayed drinking in response to electrical and thermal stimulation of the medial forebrain

Water intake in response to electrical and thermal stimulation of the medial forebrain was studied in the goat. When the frontal wall of the third cerebral ventricle was included in a field of bipolar electrical stimulation a dipsogenic response was obtained after discontinuation of the stimulation. Release of antidiuretic hormone (ADH) was apparently also elicited. The water intake was roughtly proportional to the amount of current which had been applied during the stimulation period. Water consumption in response to stimulation attenuated the dipsogenic effect of subsequent stimulation, as did also pre-stimulatory hydration by stomach tube. A 2 degrees C elevation of the temperature of parts of the preoptic/anterior hypothalamic region for 40 min periods incuded cumulative drinking starting after 2.5 to 18 min. There were great interindividual differences in the amount of water consumed in response to the thermal stimulation, possibly due to variations in thermo-couple electrode placement. The dipsogenic effect of forebrain warming was inhibited by pre-hydration, and by lowering of the environmental temperature. The delayed thirst responses are discussed in relation to stimulus-bound drinking previously observed in the same and other species. It appears possible that the delayed drinking was a manifestation of artificially induced excitation of juxtaventricular "thirst" receptors.