Actions of substance P and opiates in the rat substantia nigra

Abstract

The actions of iontophoretically applied substance P, morphine and met-enkephalin on single neurones in the substantia nigra and overlying reticular formation were investigated. None of these agents affected nigrostriatal compacta neurones, however, reticulata and reticular formation neurones were often excited by morphine and substance P, and the latter inhibited by met-enkephalin. These results suggest that activation of the dopaminergic nigrostriatal pathway by these substances may be mediated indirectly, possibly via reticulata or reticular formation neurones.