Distribution of reticulocerebellar neurons in chicken reticular formation.

The distribution of reticulocerebellar (RC) neurons was examined by the retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin bound to HRP (WGA-HRP) in 7 White Leghorn chickens. A large number of labeled cells were found in the nucleus reticularis pontis caudalis (RP) of the pontomedullary junction and in the nucleus reticularis gigantocellularis (Rgc), parvocellularis (Rpc), subtrigiminalis (Rst), paragigantocellularis (Rpg) and paramedianus (RpaM) in the medulla. Slightly ventral to the vestibulocochlear nerve were many large RC neurons arranged in a longitudinal manner along the lateral edge of the brainstem reticular formation (the Dorsolateral edge cells, DLe cells). RC neurons were most numerous in the Rgc and accounted for 31.9% of the total number of labeled cells, followed by RP (24.2%), Rpc (12.7%), Rpg (10.8%), RpaM (6.7%), DLe cells (6.3%) and Rst (4.9%). The great number of RC neurons was found around the levels of the vestibulocochlear nerve.