Dopaminergic Modulation of Motor Maps in Rat Motor Cortex: An In Vivo Study

Abstract While the primary motor cortex (M1) is know to receive dopaminergic projections, the functional role of these projections is poorly characterized. Here, it is hypothesized that dopaminergic signals modulate M1 excitability and somatotopy, two features of the M1 network relevant for movement execution and learning. To test this hypothesis, movement responses evoked by electrical stimulation using an electrode grid implanted epidurally over the caudal motor cortex (M1) were assessed before and after an intracortical injection of D1- (R-(+),8-chloro,7-hydroxy,2,3,4,5,-tetra-hydro,3-methyl,5-phenyl,1-H,3-benzazepine maleate, SCH 23390) or D2-receptor (raclopride) antagonists into the M1 forelimb area of rats. Stimulation mapping of M1 was repeated after 24 h. D2-inhibition reduced the size of the forelimb representation by 68.5% ( P