Changes in striatal dopamine D3 receptor regulation during expression of and recovery from MPTP-induced parkinsonism

Striatal dopamine (DA) D3 receptor density (measured by quantitative recept or autoradiography) and mRNA expression (measured by reverse transcriptase- polymerase chain reaction) were analyzed in cats symptomatic for and recove red from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkin sonism. In symptomatic cats. D3 receptor density was significantly decrease d in all regions of the caudate nucleus (CD) (66-77%), the nucleus accumben s (NACC) (52-83%) and the islands of calleja (IC) (67%), all of which retur ned to normal values in recovered cats. In contrast, D3 receptor mRNA expre ssion was slightly elevated in symptomatic cats, and significantly increase d above normal in recovered cats (45% increase in the CD and 91% in the NAC C). Thus, reduction of parkinsonian signs was related to normalization of s triatal D3 receptor number. These alterations in D3 receptor expression may play an important role in the recovery process observed in this model of p arkinsonism. (C) 2001 Published by Elsevier Science B.V.