Neonatal copper deficiency produced alterations in central neurotransmitter receptors that were selective with respect both to brain region and to neurotransmitter receptor type. Both high- and low-affinity dopamine receptor densities in the corpus striatum were significantly lowered, 55% and 29%, respectively, when expressed on a wet weight basis. There was a significant decrease in the level of muscarinic receptors in the striatum whether expressed on the basis of wet weight (50%) or protein (27%). A smaller reduction in muscarinic receptor density was observed in the cortex, whereas there was no effect of copper deficiency in the cerebellum. The treatment did not change beta-adrenergic receptor binding in either the cortex or cerebellum. The affinities of the receptors for the ligands was not affected by the low-copper diet. It was previously reported that copper deficiency produces regionally specific decreases in the concentrations of dopamine and norepinephrine. The greatest reduction occurred in the concentration of dopamine in the corpus striatum. The results from both studies suggest that copper deficiency in post-weanling rats may induce a selective morphological lesion.