Tyrosine hydroxylase-containing fibres extend from the rat corpus striatum into grafts of muscularis externa and myenteric plexus.

Intrastriatal grafts of myenteric plexus produce a vigorous sprouting response in the surrounding rat brain. Since the striatum receives profuse dopaminergic innervation from the substantia nigra, we have investigated whether central catecholaminergic neurons participated in the sprouting response and grew into grafts of adult myenteric plexus (surrounded by smooth muscle) implanted in the adult corpus striatum. Three weeks after implantation, tyrosine hydroxylase-containing fibres were observed to have grown into, and ramified within, the grafts. The extent of innervation was increased 6 weeks after implantation, and was not diminished if the superior cervical ganglia were removed (to destroy any fibres of sympathetic origin).