EFFECTS OF THE ALPHA-RECEPTOR LIGAND SR 31742A ON NEUROTENSIN BIOSYNTHESIS IN RAT BASAL GANGLIA

The effects of SR 31742A, a specific a ligand, were investigated on ne urotensin (NT) biosynthesis in the basal ganglia of the rat. Both sing le and repeated treatments with either SR 31742A (20 mg/kg i.p.) or ha loperidol (1 mg/kg i.p.) increased the concentration of NT-like immuno reactivity (NT-li) in the nucleus accumbens. In contrast to haloperido l, the administration of SR 31742A failed to increase the concentratio n of NT-K in the caudate-putamen We have further investigated drug-ind uced variations in NT biosynthesis by studying NT/neuromedin N (NT/NN) mRNA levels in the nucleus accumbens and the ventral tegmental area o f the rat following SR 31742A administration The NT/NN mRNA levels in the ventral tegmental area were increased by a maximum of fifteen fold (7 h at 20 mg/kg i.p.). A lower increase in NT/NN mRNA levels was eli cited in the nucleus accumbens. These results suggest that the increas e in NT-li observed after SR 31742A treatment, like that produced by h aloperidol, may result from an increase of NT biosynthesis. Furthermor e, the effects of SR 31742A on NT metabolism are similar to those of a typical antipsychotics, since they appear to be selective for the limb ic system. (C) 1995 Wiley-Liss, Inc.