Phencyclidine alters regional concentrations of neuropeptide Y and peptide YY in rat brain.

The psychotomimetic effects of Phencyclidine (PCP) often have a delayed onset and extend far from the time plasma drug levels reach their peak. PCP at a low dose is considered selective for actions on the N-methyl-D-aspartate-PCP receptor. We evaluated effects of PCP (2 and 10 mg/kg, IP) on regional content of neuropeptide Y (NPY)-like immunoreactivity (LI) and peptide YY (PYY)-LI, in the rat brain. Thirty minutes after administration of PCP, NPY-LI levels were significantly elevated in some limbic structures following both doses. A significant, widespread increase in NPY-LI levels was induced 2 hours after administration of the higher dose of PCP. On the contrary, NPY-LI was significantly decreased in a number of the regions 24 hours after PCP. The extent of reduction was less following the higher dose of PCP than following the lower dose. PCP did not cause a consistent effect on PYY-LI. The findings suggest that effects of PCP on brain NPY content might depend on the dose and the interval between administration of the drug and sacrifice.