The anterior piriform cortex (APC) may house the sensor for essential amino acid homeostasis in the brain. Several lines of evidence suggest that the APC is activated shortly after ingestion of an amino acid deficient diet. We examined the averaged evoked potentials elicited in the APC by stimulation of the lateral olfactory tract, in awake, behaving rats before and after feeding basal (BAS), threonine devoid (DEV), or corrected (COR) diets to determine directly whether the APC is activated after eating a DEV diet. When fed the DEV diet, the absolute values for the amplitude of the first negative wave differed by 36.8 ± 5.8% (P≤ 0.005) from that seen after eating the BAS diet. The latency to the second negative wave was altered by 17.2 ± 3.7% (P ≤ 0.02) compared with BAS. These results were seen by 3 h after introduction of the diet, and show that the APC is indeed activated after ingestion of a DEV diet. Also, the responses to COR returned to BAS levels by 3 h. This supports the hypothesis that the APC is important both for rejection of the DEV diet and for the recognition of the replenishment of the limiting amino acid by the COR diet.
Keywords: Amino acid imbalance; Anorexia; Area tempestas; Averaged evoked potentials; Homeostasis; Learning.