Protection and regeneration of nigral dopaminergic neurons by neurturin orGDNF in a partial lesion model of Parkinson's disease after administrationinto the striatum or the lateral ventricle
C. Rosenblad et al., Protection and regeneration of nigral dopaminergic neurons by neurturin orGDNF in a partial lesion model of Parkinson's disease after administrationinto the striatum or the lateral ventricle, EUR J NEURO, 11(5), 1999, pp. 1554-1566
Both glial cell line-derived neurotrophic factor (GDNF) and its recently di
scovered congener, neurturin (NTN), have been shown to excert neuroprotecti
ve effects on lesioned nigral dopamine (DA) neurons when administered at th
e level of the substantia nigra. In the present study, we have explored the
relative in vivo potency of these two neurotrophic factors using two alter
native routes of administration, into the striatum or the lateral ventricle
, which may be more relevant in a clinical setting. In rats subjected to an
intrastriatal (IS) 6-hydroxydopamine (6-OHDA) lesion, GDNF and NTN were in
jected every third day for 3 weeks starting on the day after the 6-OHDA inj
ection. GDNF provided almost complete (90-92%) protection of the lesioned n
igral DA neurons after both IS and intracerebroventricular (ICV) administra
tion. NTN, by contrast, was only partially effective after IS injection (72
% sparing) and totally ineffective after ICV injection. Although the trophi
c factor injections protected the nigral neurons from lesion-induced cell d
eath, the level of expression of the phenotypic marker, tyrosine hydroxylas
e (TH), was markedly reduced in the rescued cell bodies. The extent of 6-OH
DA-induced DA denervation in the striatum was unaffected by both types of t
reatment; consistent with this observation, the high rate of amphetamine-in
duced turning seen in the lesioned control animals was unaltered by either
GDNF or NTN treatment. In the GDNF-treated animals, and to a lesser extent
also after IS NTN treatment, prominent axonal sprouting was observed within
the globus pallidus, at the level where the lesioned nigrostriatal axons a
re known to end at the time of onset of the neurotrophic factor treatment.
The results show that GDNF is highly effective as a neuroprotective and axo
n growth-stimulating agent in the IS 6-OHDA lesion model after both IS and
ICV administration. The lower efficacy of NTN after IS, and particularly IC
V, administration may be explained by the poor solubility and diffusion pro
perties at neutral pH.