The Journal of Neuroscience, February 15, 1999, 19(4):1416-1423
GDNF Protection against 6-OHDA-Induced Reductions in
Potassium-Evoked Overflow of Striatal Dopamine
Wayne A.
Cass and
Michael W.
Manning
Department of Anatomy and Neurobiology, University of Kentucky
College of Medicine, Lexington, Kentucky 40536-0298
Glial cell line-derived neurotrophic factor (GDNF), when
administered before 6-hydroxydopamine (6-OHDA), has been shown to prevent the reduction in nigral dopamine (DA) levels and tyrosine hydroxylase-positive neurons normally observed after 6-OHDA lesions. The present study examined the ability of GDNF to prevent
6-OHDA-induced reductions in striatal DA release and reductions in
striatal and nigral DA levels. GDNF (10 µg), or vehicle, was injected
into the right nigra of anesthetized male Fischer-344 rats and was followed 6 hr later by intranigral 6-OHDA or saline. Three to four
weeks later the animals were anesthetized with urethane and prepared
for in vivo electrochemistry. Potassium-evoked overflow of DA was dramatically decreased in the right striatum of the vehicle + 6-OHDA-treated animals. GDNF appeared to prevent the reduction in
evoked overflow of DA in the right striatum of the 6-OHDA-treated
animals. However, in comparison with that in animals that received GDNF + saline, the overflow of DA was significantly reduced in the GDNF + 6-OHDA animals. Similarly, although nigral levels of DA were above
normal in the GDNF + 6-OHDA-treated animals, they were below DA levels
found in GDNF + saline-treated rats. Striatal DA levels were partially
protected by GDNF. In animals examined 10-12 weeks after the GDNF and
6-OHDA treatments, the apparent protective ability of GDNF on the
evoked overflow of DA in the striatum was diminished. Thus, although
intranigral GDNF can prevent 6-OHDA-induced reductions in nigral DA
levels, long-term protection of the evoked overflow of DA in the
striatum is minimal.
Key words:
GDNF; 6-hydroxydopamine; striatum; dopamine; neurotrophic
factor; in vivo electrochemistry; neurotoxicity
Copyright © 1999 Society for Neuroscience 0270-6474/99/1941416-08$05.00/0