NEUROMEDIN N IS A POTENT MODULATOR OF DOPAMINE D(2) RECEPTOR AGONIST BINDING IN RAT NEOSTRIATAL MEMBRANES

In the concentration range of 1-10 nM, neuromedin N produced a signifi cant concentration-related increase in the K(d) values of [H-3]L-(-)-N -propylnorapomorphine binding sites in rat neostriatal membranes with a peak action at 10 nM (36% increase versus the control group mean val ue). The B(max) values were not affected by neuromedin N. Neurotensin at 10 nM induced an increase in the K(d) values, which was not affecte d by a threshold concentration of neuromedin N (0.1 nM). In view of th e higher potency of neuromedin N versus neurotensin to modulate neostr iatal D2 receptors in contrast to the higher potency of neurotensin ve rsus neuromedin N to bind to the cloned neurotensin receptors, it seem s possible that the neuromedin N activated neostriatal neurotensin rec eptors controlling the D2 receptors represent a distinct subtype of ne urotensin receptors.