TH protein and mRNA in nigrostriatal dopaminergic neurons are down-regulated by continuous but not intermittent apomorphine.
Levels of tyrosine hydroxylase (TH) and TH mRNA were measured after administration of dopamine agonists for a long period of time to elucidate the long-term feedback inhibition of dopamine synthesis in nigrostriatal dopaminergic neurons. Continuous infusion, which desensitized presynaptic dopamine receptors, but not repeated administration, down-regulated TH and TH mRNA levels. This suggests levels of TH protein and mRNA are only feedback inhibited by the continuous stimulation of postsynaptic dopamine receptors.
Iwata
S
S
Department of Pharmacology, Faculty of Medicine, Kagoshima University, 890-8520, Kagoshima, Japan. shinichi@m.kufln.kagoshima-u.ac.jp
Nomoto
M
M
Kaseda
S
S
Tanoue
S
S
Shimosaka
M
M
Fukuda
T
T
D000818:Animals; D001058:Apomorphine / Q000008:administration & dosage / Q000494:pharmacology*; D001971:Bromocriptine / Q000494:pharmacology; D003342:Corpus Striatum / Q000201:enzymology*; D004298:Dopamine / Q000502:physiology*; D004334:Drug Administration Schedule; D007839:Functional Laterality; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D008297:Male; D008636:Mesencephalon / Q000201:enzymology; D009474:Neurons / Q000201:enzymology*; D014176:Protein Biosynthesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000201:enzymology*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics*
D012333:RNA, Messenger; D001971:Bromocriptine; D014446:Tyrosine 3-Monooxygenase; D001058:Apomorphine; D004298:Dopamine