Selective effects of partial and severe lesions of the serotonergic systems on Met-enkephalin and substance P neurons in rat basal ganglia.
The effects of partial (80%) vs. severe (> 95%) depletion of serotonin (5-HT) on peptide expression in basal ganglia were examined using immunocytochemical and in situ hybridization histochemical approaches. Topographical analysis of the changes in Met-enkephalin (Met-enk) and substance P (SP) levels were performed on the rat striatum, globus pallidus and substantia nigra 3 weeks after injecting 3 microl (partial lesion) or 6 microl (severe lesion) 5,7-dihydroxytryptamine (6.6 microg/microl) into the anterior raphe nuclei. Both kinds of lesion led to significant increases (39-42%) in Met-enk immunoreactivity in the striatum; a corresponding increase (21%) was detected in the globus pallidus only after severe 5-HT depletion. Only the severe lesion increased the SP immunoreactivity in the striatum (32%) and substantia nigra (26%). Neither striatal preproenkephalin nor preprotachykinin levels showed significant differences with the control values. These results suggest that the neuronal accumulation of Met-enk or SP may be attributable to post-transcriptional events, such as a blockade of the peptide release, and that 5-HT may, thus, exert a facilitatory influence on the striatal output neurons. The results obtained after partial lesion indicate a preferential sensitivity of striatal Met-enk vs. SP containing terminals to the 5-HT denervation. These differences are illustrated in selective regional changes in peptide labeling. These data point to some balance exerted by the serotonergic and dopaminergic inputs on these neuronal populations.
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Laboratoire de Neurobiologie Cellulaire et Fonctionnelle, CNRS, UPR-9013, Marseille, France.
Salin
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Daszuta
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D000818:Animals; D001479:Basal Ganglia / Q000737:chemistry* / Q000166:cytology; D004744:Enkephalin, Methionine / Q000032:analysis*; D005260:Female; D006651:Histocytochemistry / Q000379:methods; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009434:Neural Pathways / Q000187:drug effects; D009474:Neurons / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000502:physiology*; D013373:Substance P / Q000032:analysis*
D012701:Serotonin; D013373:Substance P; D004744:Enkephalin, Methionine