Opioid binding sites in the nigrostriatal system of the guinea pig are not located on nigral dopaminergic neurons.

Unilateral 6-hydroxydopamine injection into the compact zone of the guinea pig substantia nigra was used to destroy nigral dopamine neurons. The glyoxylic acid method for monoamine fluorescence was employed to ascertain the loss of dopaminergic fibers in the striatum and substantia nigra. It could be shown that there was no change in the number of [3H](-)-bremazocine binding sites in the substantia nigra or the striatum on the lesioned side of these guinea pigs.