Changes in dopamine D 1 and D 2 receptor binding in the substantia nigra following intrastriatal injection of a retrograde neurotoxin (volkensin)

Abstract

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 pars compacta (SNc) cell number on the ipsilateral side as compared to the contralateral side. This decrease was associated with a 35–56% decrease in [ 3H]sulpiride binding to dopamine D 2 receptors in the SNc. In the substantia nigra pars reticulata (SNr) there was a 17–24% decrease in [ 3H]SCH 23390 binding to dopamine D 1 receptors on the ipsilateral as compared to the contralateral side. The cell loss and decrease in D 2 binding is attributed to the retrograde neurotoxic properties of volkensin. The decrease in D 1 binding is believed to reflect loss of presynaptic receptors from terminals of striato-nigral neurons, and thus the anterograde neurotoxicity of volkensin.