DEMONSTRATION OF AXON COLLATERAL PROJECTIONS FROM THE SUBSTANTIA-NIGRA PARS RETICULATA TO THE SUPERIOR COLLICULUS AND THE PARVICELLULAR RETICULAR-FORMATION IN THE RAT

It was revealed in the rat that single neurons in the substantia nigra pars reticulata (SNr) innervated both the superior colliculus (SC) an d the parvicellular reticular formation (RFp) in the pens and medulla oblongata by way of axon collaterals. After injecting Fluoro-gold into the lateral part of the SC and Fluoro-ruby into the RFp on the same s ide, some SNr neurons were double-labeled with both tracers. They were localized in the dorsolateral part of the caudal half of the SNr ipsi lateral to the injection sites.