Chapter 58 Possible mechanisms of action of adrenal transplants in Parkinson's disease

Abstract

Publisher Summary This chapter examines the possible mechanisms of action of adrenal transplants in Parkinson's disease. The contralateral grafts of fetal adrenal medulla or substantia nigra can ameliorate apomorphine-induced rotational behavior for extended periods of time in rats with unilateral 6-hydroxydopamine (6-OHDA) denervation of the nigrostriatal pathway. As adrenal medulla grafts do not increase dopamine levels in cerebrospinal fluid (CSF), but blood levels of dopamine are increased after such transplants, dopamine may gain access to the striatum via the systemic circulation. Adrenal medulla transplants in the aged rats not only induce a recovery of motor deficits but seem to reactivate dopaminergic transmission in the naturally degenerated nigro-striatal pathway, as shown by tyrosine hydroxylase (TH)-immunocytochemical staining. Similar observations of an enhanced morphological and functional recovery of nigro-striatal dopaminergic fibers by adrenal medulla grafts are described in the chapter. The role of trophic factors may be critical for this reactivation, because nerve growth factor plus noncatecholaminergic grafts reduces motor disfunctions in aged rats. The additional fact that adrenal transplants increase pain thresholds in the presence of dibutyryl cyclic adenosine monophosphate (cAMP), suggesting that chromaffin cells may have multiple biochemical actions, which in turn produce multiple effects when transplanted into the brain.