Neuropeptide Y and somatostatin in the anterior piriform cortex alter intake of amino acid deficient diets

Neuropeptides affect food intake via peripheral and brainstem mechanisms, but their roles in mediating feeding via the cerebral cortex have received little attention. The anterior piriform cortex (APC) appears to play a critical role in neuroperception of deficiencies of essential amino acids (AA) and the anorectic response to such deficiencies. The neural circuitry underlying the role of this paleocortex in these events is not understood. We have shown that neurons containing neuropeptide Y (NPY) and somatostatin (SOM) are cytoarchitecturally in positions to relate synaptically to the neurons of the APC which may mediate responses to AA. Thus, we hypothesized that NPY and SOM administered intracortically to the APC would directly affect food intake in a threonine-imbalanced model. We determined that NPY at 1-1.5 nmol decreased intake of the AA-deficient diet for 3 h, with a cumulative effect that extended through 6 h. SOM had a dual effect; at 1 pmol it increased intake of the AA-deficient diet for 3 h; at 2 nmol, SOM decreased intake of the AA-deficient diet for over 9 h, with a cumulative effect that persisted through 12 h. In the first 3 h, intake of animals receiving 1 pmol of SOM differed significantly from those receiving 2 nmol. These results suggest that NPY and SOM affect the cortical circuitry responsible for recognition of deficiencies in nutritionally essential AA, and that the timing of the cortical responses to the peptides may be related to the time course of the anorectic responses. (C) 1998 Elsevier Science Inc.