four contiguous areas contained da-immunostained nerve cell bodies : ( 1 ) the substantia nigra , pars compacta ( snc ) , ( 2 ) the ventral tegmental area ( vta ) , ( 3 ) the retrorubral area ( rra ) , and ( 4 ) the periaqueductal gray ( pag ) .
C0038590
substantia nigra
C0175412
pars compacta