An EM and Golgi study on the connection between the nucleus tegmenti pedunculopontinus and the pars compacta of the substantia nigra in the rat.

The present study provides evidence of a synaptic contact between terminals of pedunculopontine neurons and cells of substantia nigra pars compacta (SNPC) in the rat. Three types of projective neurons observed in Golgi stained preparations of the pedunculopontine region might be the source of this afferent pathway to the substantia nigra. These PPN projective neurons were small, medium and large sized cells. After placing a small electrolytic lesion into the pedunculopontine area two types of degenerated terminals were found in the SNPC, a small and a larger one. These degenerated terminals contained round synaptic vesicles, thus suggesting that the pedunculopontine input to the SNPC is monosynaptic and excitatory in nature.