CHANGES IN DOPAMINE-D(1) AND DOPAMINE-D(2) RECEPTOR-BINDING IN THE SUBSTANTIA-NIGRA FOLLOWING INTRASTRIATAL INJECTION OF A RETROGRADE NEUROTOXIN (VOLKENSIN)

The neurotoxic properties of the proposed retrograde neurotoxin volkensin were investigated. Unilateral intrastriatal injections of volkensin (n = 8) caused a 60-79% decrease in substantia nigra compacta (SNc) cell number on the ipsilateral side as compared to the contralateral side. This decrease was associated with a 35-56% decrease in \H-3]sulpiride binding to dopamine D2 receptors in the SNc. In the substantia nigra pars reticulata (SNr) there was 17-24% decrease in [3II]SCH 23390 binding to dopamine D1 receptors on the ipsilateral as compared to the contralateral side. The cell loss and decrease in D2 binding is attributed to the retrograde neurotoxic properties of volkensin. The decrease in D1 binding is believed to reflect loss of presynaptic receptors from terminals of striato-nigral neurons, and thus the anterograde neurotoxicity of volkensin.