Neuroendocrine and behavioural responses to hyperosmolality in rats with lesions of the lateral hypothalamus made by N-methyl-D-aspartate.

Excitotoxic lesions of rat lateral hypothalamus produce impairments in eating and drinking, but not motor deficits. However, it has not been established what causes these eating and drinking impairments. In the present experiments, drinking, plasma osmolality and arginine-vasopressin concentration were measured in lateral hypothalamic-lesioned and control rats following systemic injection of hypertonic saline. In response to hyperosmolality, N-methyl-D-aspartate-lesioned rats drank significantly less than controls but showed normal increases in plasma osmolality and arginine-vasopressin concentration. This dissociation of neuroendocrine and behavioural responses suggests that the impairment of rats with excitotoxic lesions of the lateral hypothalamus is unrelated to physiological (as opposed to behavioural) mechanisms of homeostasis.