Volume 16, Number 24,
Issue of December 15, 1996
pp. 8132-8139
Copyright ©1996 Society for Neuroscience
GDNF Selectively Protects Dopamine Neurons over Serotonin Neurons
Against the Neurotoxic Effects of Methamphetamine
Received May 30, 1996; revised Sept. 24, 1996; accepted Sept. 27, 1996.
Wayne A. Cass
Department of Anatomy and Neurobiology, University of Kentucky
College of Medicine, Lexington, Kentucky 40536
Repeated methamphetamine (METH) administration to animals can
result in long-lasting decreases in striatal dopamine (DA) and serotonin (5-HT) levels. Glial cell line-derived neurotrophic factor (GDNF) has pronounced effects on dopaminergic systems in vivo, including partial neuroprotective effects against
6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
-induced lesions. The present study examined the ability of GDNF to
prevent METH-induced reductions in potassium-evoked overflow of DA, and
DA and 5-HT content, in striatum. GDNF (10 µg) or vehicle was
injected into the right striatum of anesthetized rats. Twenty-four
hours later, the rats were injected four times at 2 hr intervals with
METH (5 mg/kg, s.c.) or saline. One week later, in vivo
electrochemistry was used to monitor the overflow of DA evoked by local
potassium application. Evoked overflow of DA was dramatically decreased in the striatum of METH-treated animals. GDNF prevented the reduction in evoked overflow of DA in the right striatum of the METH-treated animals. After each experiment, the animals were killed, and striatal DA and 5-HT levels determined by HPLC. The METH treatment produced significant decreases in both neurotransmitters. GDNF administration prevented the reduction in striatal DA levels on the treated side of
the brain, whereas levels on the contralateral side were still decreased. In dose-response studies, 1 µg of GDNF was as protective as 10 µg, whereas 0.1 µg was only partially protective. In
contrast, 5-HT levels were only minimally protected by previous
administration of GDNF. These results suggest that GDNF can selectively
protect DA neurons, compared with 5-HT neurons, against the neurotoxic effects of METH.
Key words:
GDNF;
methamphetamine;
striatum;
dopamine;
serotonin;
neurotrophic factor;
in vivo electrochemistry;
neurotoxicity