AREA POSTREMA LESIONS IN RATS APPEAR TO DISRUPT RAPID FEEDBACK INHIBITION OF FLUID INTAKE

Area postrema lesions (APX) were produced by vacuum aspiration in adul t male rats. After systemic administration of hypertonic saline soluti ons, significantly more water was consumed by rats with APX than by in tact control rats. Similarly enhanced water intake by rats with APX al so was observed when marked hypovolemia was induced by s.c. administra tion of a hyperoncotic colloidal solution. In both conditions, the inc reased water intake occurred within the first 15 min of the drinking t ests. Intakes of liquid diet or 10% sucrose solution after food depriv ation by rats with APX also were considerably larger than those of con trol rats. These and other results suggest that rats with APX experien ce less inhibition of ingestion while drinking. Thus, the AP may be im portant for the detection of early, inhibitory signals generated by fl uid ingestion, and after its ablation increased drinking may occur bec ause the feedback inhibition provided by such signals is diminished.