Characterization of behavioral and neurodegenerative changes following partial lesions of the nigrostriatal dopamine system induced by intrastriatal 6-hydroxydopamine in the rat.
Partial lesions of the nigrostriatal dopamine system have been investigated with respect to their ability to induce consistent long-lasting deficits in movement initiation and skilled forelimb use. In eight different lesion groups 6-hydroxydopamine (6-OHDA) was injected at one, two, three, or four sites into the lateral sector of the right striatum, in a total dose of 20-30 microgram. Impairments in movement initiation in a forelimb stepping test, and in skilled paw use in a paw-reaching test, was seen only in animals where the severity of the lesion exceeded a critical threshold, which was different for the different tests used: single (1 x 20 microgram) or two-site (2 x 10 microgram) injections into the striatum had only small affects on forelimb stepping, no effect on skilled paw use. More pronounced deficits were obtained in animals where the same total dose of 6-OHDA was distributed over three or four sites along the rostro-caudal extent of the lateral striatum or where the injections were made close to the junction of the globus pallidus. The results show that a 60-70% reduction in tyrosine hydroxylase (TH)-positive fiber density in the lateral striatum, accompanied by a 50-60% reduction in TH-positive cells in substantia nigra (SN), is sufficient for the induction of significant impairment in initiation of stepping. Impaired skilled paw-use, on the other hand, was obtained only with a four-site (4 x 7 microgram) lesion, which induced 80-95% reduction in TH fiber density throughout the rostrocaudal extent of the lateral striatum and a 75% loss of TH-positive neurons in SN. Drug-induced rotation, by contrast, was observed also in animals with more restricted presymptomatic lesions. The results indicate that the four-site intrastriatal 6-OHDA lesion may be a relevant model of the neuropathology seen in parkinsonian patients in a manifest symptomatic stage of the disease and may be particularly useful experimentally since it leaves a significant portion of the nigrostriatal projection intact which can serve as a substrate for regeneration and functional recovery in response to growth promoting and neuroprotective agents.
Department of Physiology and Neuroscience, Lund University, Sölvegatan 17, Lund, 223 62, Sweden.
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Kirik
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Rosenblad
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Björklund
D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D003342:Corpus Striatum / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D005260:Female; D005552:Forelimb / Q000294:innervation; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D009410:Nerve Degeneration / Q000503:physiopathology*; D009474:Neurons / Q000201:enzymology; D016627:Oxidopamine; D011597:Psychomotor Performance / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012399:Rotation; D013378:Substantia Nigra / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis
D016627:Oxidopamine; D000661:Amphetamine; D014446:Tyrosine 3-Monooxygenase; D001058:Apomorphine; D004298:Dopamine