The presence of a single class of high affinity, saturable binding sites for [3H]neuropeptide Y (NPY) was demonstrated in membranes from human frontal and temporal cortex. The specific binding of [3H]NPY was sensitive to guanosine 5'-triphosphate (GTP) and guanylyl-imidodiphosphate (GMPP(NH)P; 100 microM) which lowered the total binding capacity (Bmax) value (35 +/- 2 fmol/mg in the frontal cortex and 82 +/- 3 fmol/mg in the temporal cortex) by 50%. GTP and GMPP(NH)P did not affect the dissociation constant (Kd) value which was 0.25 +/- 0.03 nM in a frontal cortex sample and 0.76 +/- 0.06 nM in the sample from the temporal cortex. The affinity and GTP sensitivity of the [3H]NPY binding to human brain membranes parallels that found in the rat brain. It was demonstrated that occupancy of NPY receptors by NPY (1 microM) inhibits the basal and forskolin (10 microM)-stimulated adenylate cyclase activity by 18-30% in a crude membrane preparation from human frontal cortex.