Regulation of the concentration of dynorphin A1-8 in the striatonigral pathway by the dopaminergic system.
The purpose of this study was to explore the dopaminergic control of the striatonigral dynorphin system by measuring the levels of dynorphin A1-8-like immunoreactivity (DN-LI) after repeated injections of a dopaminergic receptor agonist or antagonist. Seven daily injections of different doses of apomorphine (0.5, 1.0, 2.5 and 5.0 mg/kg, s.c.) caused a significant dose-related increase of DN-LI in the striatum (26, 34, 63, 85% over control at each corresponding dose). Similar increases were observed in the substantia nigra (22, 52, 50 and 62% over control). In another experiment, rats received 5 mg/kg of apomorphine for 1, 3, and 7 days. There was a significant time-related increase in DN-LI both in the striatum (37, 50 and 85% over control at each corresponding period) and in the substantial nigra (32, 78 and 62%). Repeated administration of haloperidol (1 mg/kg, i.p.) failed to change the striatal level of DN-LI, but, when given at the same time as apomorphine, significantly attenuated the effect of apomorphine. These results suggest that dopamine exerts a modulatory influence on the metabolism of dynorphin in the striatonigral pathway.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D003342:Corpus Striatum / Q000032:analysis* / Q000502:physiology; D004298:Dopamine / Q000502:physiology*; D004399:Dynorphins / Q000032:analysis*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D010446:Peptide Fragments / Q000032:analysis*; D051381:Rats; D011916:Rats, Inbred F344; D013378:Substantia Nigra / Q000032:analysis* / Q000502:physiology; D009435:Synaptic Transmission
D010446:Peptide Fragments; D004399:Dynorphins; C026770:dynorphin (1-8); D006220:Haloperidol; D001058:Apomorphine; D004298:Dopamine