Chapter 57 Mechanisms of action of adrenal medulla grafts: the possible role of peripheral and central dopamine systems

Abstract

This chapter examines the mechanisms of action of adrenal medulla grafts. Adrenal medulla grafts reduce rotational behavior induced by both amphetamine (AMPH) and apomorpbine (APO) in animals with unilateral dopamine (DA)-denervation. The peripheral administration of DA increases extracellular striatal DA concentrations adjacent to adrenal medulla grafts, suggesting an impairment of the blood–brain barrier by the grafts. This change in extracellular DA is slight in animals with no behavioral change, modest in animals with decreased APO-induced rotation, and marked (about 10-fold) in animals with decreased AMPH-induced rotation. Changes in serum catecholamines are correlated with the decrease in APO-induced rotations following adrenal medulla grafts. The specific correlations depend upon whether the animal is adrenodoxin (ADX) or not. Adrenal chromaffin cell survival is not correlated with serum catecholamines or behavioral changes. The number of surviving chromaffin cells is small and inconsistent. Behavioral recovery (decreased APO-induced rotation) is associated with an increased symmetry of striatal extracellular DA and dihydroxyphenylacetic acid (DOPAC) concentrations as determined by microdialysis. This increased symmetry appears to be related in part to increases in DA and DOPAC concentrations on the lesioned side but also in part to decreases in DA and DOPAC concentrations on the normal, unlesioned, and ungrafted side.