The effect of catecholamine depletion or blockade of dopaminergic or noradrenergic receptors on the neuropeptide Y immunoreactivity was studied in the rat brain cortex using immunohistochemical methods. Neuropeptide Y immunoreactive neurons were counted and the mean density of stained neurons per microscopic field was calculated. It was found that monoamine depletion by reserpine, the blockade of dopaminergic receptors by haloperidol or the specific D1 receptor blockade by SCH23390 caused a significant increase in the neuropeptide Y immunoreactivity in the cortex studied, after 24 h, evaluated as the density of immunoreactive neurons. No significant changes were observed after the blockade of alpha or beta adrenergic receptors (by phenoxybenzamine or propranolol, respectively). Specific D2 receptor blockade by sulpiride induced an insignificant increase only. The results suggest the existence of an inhibitory dopaminergic control of the neuropeptide Y content, mainly via D1 receptors, in neurons of the rat brain cortex.