Neuromedin N is a potent modulator of dopamine D 2 receptor agonist binding in rat neostriatal membranes

Abstract

In the concentration range of 1–10 nM, neuromedin N produced a significant concentration-related increase in the K d values of [ 3 H] l -(−)-N- propylnorapomorphine binding sites in rat neostriatal membranes with a peak action at 10 nM (36% increase versus the control group mean value). 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 affected by a threshold concentration of neuromedin N (0.1 nM). In view of the higher potency of neuromedin N versus neurotensin to modulate neostriatal D 2 receptors in contrast to the higher potency of neurotensin versus neuromedin N to bind to the cloned neurotensin receptors, it seems possible that the neuromedin N activated neostriatal neurotensin receptors controlling the D 2 receptors represent a distinct subtype of neurotensin receptors.