Postnatal rat NADPH-diaphorase-containing myenteric neurons extend processes when transplanted into adult rat corpus striatum.

Pieces of isolated myenteric plexus, freshly dissected from the colon of young inbred Fischer rats, were implanted unilaterally into the corpus striatum of adult Fischer rats which had received a prior quinolinic acid lesion. Similar implants were made into the unlesioned striatum of a second group of Fischer rats. The survival of a subpopulation of grafted neurons, and the incidence of fiber outgrowth from these neurons into the host striatum, was examined after 3 and 6 weeks using a histochemical technique for the demonstration of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) activity. This enzyme is found both in some enteric neurons and a subpopulation of striatal neurons. Grafted enteric neurons expressing NADPH-diaphorase were easily distinguished in both the lesioned and unlesioned host striata at 3 and 6 weeks postimplantation. Fibers could be found extending from NADPH-diaphorase-containing enteric neurons into both the lesioned and unlesioned corpus striatum, although fewer graft-derived fibers were seen in the unlesioned striatum. This is the first demonstration that enteric neurons transplanted into the adult mammalian brain are capable of extending processes into the surrounding CNS tissue.