Strong effects of NT/NN peptides on DA D2 receptors in rat neostriatal sections.
Quantitative receptor autoradiography was performed to test the effects of neurotensin (NT)/neuromedin N (NN) peptides on dopamine (DA) D2 receptors in rat neostriatal sections. Competition experiments showed that 10 nM of NT, 10 nM of NN, and 1 nM of the C-terminal NT-(8-13) fragment produced a 2-fold increase in the IC50 value and a 20% decrease in the B0 value of DA for the D2 antagonist [125I]iodosulpride binding sites. The results demonstrate a stronger reduction in the affinity of DA for neostriatal D2 receptors by the NT/NN peptides in brain sections compared with membrane preparations indicating the possible involvement of cytoplasmic factors and/or a demand for a more intact membrane structure in these receptor-receptor interactions. Further evidence for the hypotheses that the C-terminal NT fragments may be among the major ligands for the neostriatal NT receptors and that the neostriatal NT receptors may be a new subtype of NT receptor has been obtained.
Li
X M
XM
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Hedlund
P B
PB
Fuxe
K
K
D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000494:pharmacology*; D009496:Neurotensin / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000187:drug effects*; D018028:Receptors, Neurotensin / Q000187:drug effects / Q000378:metabolism
D009479:Neuropeptides; D010446:Peptide Fragments; D017448:Receptors, Dopamine D2; D018028:Receptors, Neurotensin; C042090:neuromedin N; D009496:Neurotensin; C054381:neurotensin (8-13)