Intrastriatal adrenal medulla grafts in rats. Long-term survival and behavioral effects

Rats with rotational behavior consequent to unilateral lesions of the substantia nigra have been proposed for an experimental model of Parkinson's disease. Adrenal medulla or embryonic substantia nigra grafts in the lateral ventricle of these animals reduce this rotational behavior. For application to primate and human subjects, it may be necessary to implant tissue directly into the parenchyma of the corpus striatum rather than into the ventricle in order to achieve a sufficient distribution of the grafted tissues and increase the efficacy of the grafts. In the present study, the properties of intraparenchymal adrenal medulla grafts were investigated. Grafts were obtained from both young (4 to 5 weeks old) and aging (22 to 24 months old) donor rats. Much of the implanted tissue did not survive, although 200 chromaffin cells per recipient rat were found to have survived for at least 6 months. All of the surviving cells developed process-like cytoplasmic extensions, although these processes did not appear to have reinnervated host brain tissue. Grafts from both young and aging donor rats prevented a slight deterioration in the performance of a sensory neglect test that was observed in a control group that received grafts of sciatic nerve. There was also a tendency that did not reach statistical significance for grafts from young (but not from aging) donors to decrease apomorphine-induced rotational behavior. It is concluded that, although the corpus striatum does not appear to provide a particularly favorable environment for the implantation of adrenal medulla grafts, striatal implants of adrenal medulla might become a promising procedure if a means of improving the survival of these tissues could be developed.