The Journal of Neuroscience, August 1, 1999, 19(15):6643-6649
Striatal Preproenkephalin Gene Expression Is Upregulated in Acute
but Not Chronic Parkinsonian Monkeys: Implications for the Contribution
of the Indirect Striatopallidal Circuit to Parkinsonian
Symptomatology
Jay S.
Schneider,
Emmanuel
Decamp, and
Timothy
Wade
Department of Pathology, Anatomy, and Cell Biology, Thomas
Jefferson University, Philadelphia, Pennsylvania 19107
This study examined the extent of striatal dopamine (DA)
denervation and coincident expression of preproenkephalin (PPE) mRNA in
monkeys made parkinsonian by
1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration.
Some animals (n = 4) became moderately parkinsonian
after receiving large doses of MPTP over short periods of time and were
symptomatic for only a short period of time (1-3 months; acute
parkinsonian group). Other animals became moderately parkinsonian after
receiving either escalating doses of MPTP over long periods (4-6
months; n = 5) or a high dose of MPTP over a short
period (<1 month; n = 1) and remained symptomatic
for an extended period (>8 months; chronic parkinsonian group).
Despite similar symptomatology and similar degrees of striatal DA
denervation at the time of their deaths, only acute parkinsonian
animals had significantly increased PPE expression in sensorimotor
striatal regions. PPE expression in chronic parkinsonian animals was
either not changed or significantly decreased in most striatal regions. These findings suggest that the duration and not the extent of striatal
DA denervation is a critical factor in modulating changes in striatal
PPE expression. Furthermore, these results question the role of
increased activity in the enkephalin-containing indirect striatopallidal pathway in the expression of parkinsonian symptoms.
Key words:
enkephalin; striatum; parkinsonism; dopamine; monkeys; MPTP
Copyright © 1999 Society for Neuroscience 0270-6474/99/19156643-07$05.00/0