Strong effects of NT/NN peptides on DA D2 receptors in rat... : NeuroReport (original) (raw)
Neurochemistry: PDF Only
Strong effects of NT/NN peptides on DA D2 receptors in rat neostriatal sections
Division of Cellular and Molecular Neurochemistry, Department of Neuroscience, Doktorsringen 12, Karolinska Institutet, 171 77 Stockholm, Sweden
Abstract
QUANTITATIVE receptor autoradiography was performed to test the effects of neurotensin (NT)/neuromedin N (NN) pcptides on dopamine (DA) D2 receptors in rat neo-striatal 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 IC30 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.
© Lippincott-Raven Publishers.