Neuropeptide-dopamine interactions. IV. Effect of thyrotropin-releasing hormone on striatal dopaminergic neurons.
Many biologic effects of TRH seem to be mediated via a dopaminergic mechanism. The present study examined the effects of chronic TRH administration on the properties of nigrostriatal dopaminergic neurons. Ten days, continuous subcutaneous TRH administration via an osmotic minipump led to a significant rise in striatal level of 3,4-dihydroxyphenylacetic acid, but not of homovanillic acid or dopamine. These treatments also did not elicit any significant changes in the maximal binding capacity (Bmax) or affinity (KD) of either D1- or D2-dopamine receptor. By contrast, TRH administration led to a significant increase in both Bmax and KD of striatal mazindol binding. This effect of TRH, however, was not observed in in vitro studies. In conclusion, these data suggest that in vivo administration of TRH may modulate dopaminergic activities by altering, directly or indirectly, dopamine release and reuptake.
Ikegami
H
H
Department of Medicine, Louisiana State University Medical Center, New Orleans 70112.
Spahn
S A
SA
Prasad
C
C
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism*; D004294:Domperidone / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D018492:Dopamine Antagonists; D006719:Homovanillic Acid / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008454:Mazindol / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism*; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D001552:Benzazepines; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D015102:3,4-Dihydroxyphenylacetic Acid; D004294:Domperidone; D013973:Thyrotropin-Releasing Hormone; D008454:Mazindol; D004298:Dopamine; D006719:Homovanillic Acid