Parabrachial lesions disrupt responses of rats to amino acid devoid diets,to protein-free diets, but not to high-protein diets

Normal rats "reduce" intake of diets that lack an essential amino acid (THR -DEV), are protein free (PO %), or contain a high proportion of protein (P7 5%). We tested the importance of the parabrachial nuclei (PBN) in signaling such adjustments of food intake by placing electrophysiologically guided l esions in these nuclei at points that responded to gustatory stimuli. When fed the THR-DEV diet, rats with PEN lesions (PBNx) decreased their food int ake significantly less than the controls (78.5 vs. 44.4%). When put on a P0 % diet, PBNx animals decreased their intake only 8% compared with 23 % for our CONT group. When put on a P75% diet, however, both groups decreased the ir intake in an equivalent amount. These experiments show that the PEN is i nvolved in the learned aversion to an amino acid devoid diet. (C) 2000 Else vier Science Inc. All rights reserved.