Adipsia-polydipsia induced by simultaneous lesion of the medioventral septum and anteroventral third ventricle area in the rat.

The medioventral septal area (MVS) and also the tissue surrounding the periventricular preoptic-hypothalamic region (AV3V) of male rats, were destroyed by mean of electrolytic lesions. Before and after the lesions, daily water and food intakes, diuresis, body weight, urine osmolarity, and sodium and potassium excretion were determined. Rats with simultaneous AV3V-MVS lesions showed a biphasic pattern of drinking behavior characterized by a first period of adipsia followed by another period of polydipsia. During the first period of adipsia and except for the first two days, postlesion rats were able to reduce total urine volume but failed to produce an appropriate concentrated urine. During the polydipsia period, on the contrary, rats increased urine output and decreased urine osmolarity in a parallel fashion. Immediately after the lesion, food intake was decreased but recovered to pre-lesion levels gradually. By contrast, body weight was decreased during the entire period of the experiment. Sodium but not potassium excretion showed a significant increase from the 9th to the 20th day postlesion. The results suggest that the AV3V and MVS are part of a circuitry subserving the control of water intake and electrolyte balance.