Diffusible factor(s) from adult rat sciatic nerve increases cell number and neurite outgrowth of cultured embryonic ventral mesencephalic tyrosine hydroxylase‐positive neurons

Dissociated embryonic rat ventral mesencephalon containing the developing A8‐A10 dopamine (DA) neurons was cultured alone or in the presence of a 10 mm segment of adult rat sciatic nerve that had been explanted and maintained in separate culture for 72 hours prior to introduction to mesencephalic cultures. Nerve segments were contained in a co‐culture basket, so that midbrain cells and nerve shared medium but were not in physical contact. The number and morphology of cultured DA neurons was assessed via immunocytochemistry for tyrosine hydroxylase (TH). Co‐cultures of ventral midbrain tissue and nerve exhibited an increased number of TH‐positive neurons, with larger neuronal perikarya, and increased length and complexity of neurites, than cultures of midbrain tissue alone. Increased number and growth of TH‐positive neurons was obtained with as little as 2 days of exposure to nerve. This evidence suggests that a diffusible, soluble factor(s) from sciatic nerve can enhance the number and development of TH‐positive neurons detected in cultures of embryonic ventral mesencephalon.