Neuropeptide Y, somatostatin, and cholecystokinin of the anterior piriform cortex

In addition to its role in olfaction and as a primary epileptogenic site, the anterior piriform cortex has been suggested to play a role in neuroperception of deficiencies or imbalances in physiologically essential amino acids. In recent studies, amino acid deficient diets were shown to induce expression of c-fos in the anterior piriform cortex within the rapid time frame associated with the normal anorectic response to such diets. It became important to examine the neurocytochemical architecture of this region for clues as to how and more precisely where dietary amino acid deficiency or imbalance might be monitored. The relationships of neuropeptide Y-, somatostatin-, and cholecystokinin-containing neurons were of particular interest because ongoing studies indicate that those peptides administered to the anterior piriform cortex alter intake of diets deficient in essential amino acids. The neuropeptides were endogenous to intrinsic neurons only; none resembled pyramidal projection neurons. Peptidergic neurons and fibers were concentrated most heavily in layer III of the paleocortex. The cytoarchitecture suggests that neuropeptide Y-, somatostatin-, and cholecystokin-containing neurons of the anterior piriform cortex may relate synaptically or multisynaptically to local circuit neurons during electrical activity, modulation of olfactory information, and neuroperception of essential amino acids.