Changes in paroxetine binding in the cerebral cortex of polydipsic rats.

Schedule-induced polydipsia was induced when food-deprived rats were subjected to a fixed-time (60 s) feeding schedule for 150 min daily for 3 weeks (training period). Subsequent chronic administration of the serotonin reuptake inhibitor fluoxetine reduces schedule-induced polydipsia over 2-4 weeks. We asked whether changes in the serotonin reuptake carrier occur following the development of schedule-induced polydipsia and its reduction by fluoxetine. Using [3H]paroxetine binding, we found a 40% increase in Kd and a 50% decrease in Bmax in polydipsic rats; both were reversed by fluoxetine. Food deprivation alone did not affect these parameters. These observations suggest that changes in the serotonin reuptake carrier correlate with the development and reversal of schedule-induced polydipsia.