Muscarinic cholinergic binding in striatal and mesolimbic areas of the rat: reduction by 6-hydroxydopa.

The pilocarpine-induced catalepsy and the specific binding of ³H]quinuclidinyl benzilate (³H]QNB) in synaptic membranes were investigated in the adult rat neonatally treated with 6-hydroxydopa (6-OHDOPA). An i.p. administration of pilocarpine (75–150 mg/kg) elicited less catalepsy in the 6-OHDOPA-treated rats than in the controls. The specific binding of ³H]QNB in the striatal or mesolimbic homogenates proved to be saturable. In addition, treatment with 6-OHDOPA caused a significant reduction in B_max values of ³H]QNB binding in both regions but did not alter the K_D values as compared with those of the controls. These results suggest that neonatal treatment with 6-OHDOPA induces a muscarinic-cholinergic hyposensitivity in the rat brain which is probably due to the decrease in the number of muscarinic-cholinergic receptors in the striatal and/or mesolimbic areas.