Protein Synthesis in the Prepyriform Cortex: Effects on Intake of an Amino Acid-Imbalanced Diet by Sprague-Dawley Rats

Abstract

The effect of inhibiting protein synthesis within the prepyriform cortex (PPC) on intake of an amino acid imbalanced diet was evaluated in rats receiving bilateral injections of the dietary limiting amino acid (DLAA). Injection of the DLAA into the PPC increased intake of the imbalanced diet by 150% and incorporation of [³H]leucine into the trichloroacetic acid insoluble fraction of PPC homogenates by 248%. Coinjection of puromycin (100 µmol/L) or actinomycin D (10 µmol/L) blocked the increase in intake of the imbalanced diet but had no effect on intake of the basal diet. Puromycin blocked the increase in intake of the imbalanced diet whether injected with the DLAA or 6 h later. Selection of the imbalanced diet over a protein-free diet when the DLAA was administered was blocked by co-injecting puromycin or actinomycin D. The results indicated that the increased intake and the reversal of aversion to the imbalanced diet when the DLAA was injected into the PPC required de novo protein synthesis. The proteins necessary for the feeding response seemed to have a short half-life and seemed to require synthesis of new mRNA. We conclude that changes in concentration of the DLAA within the PPC influenced protein synthesis at the genomic level.