REPEATED ACTIVATION OF NEUROTENSIN RECEPTORS SENSITIZES TO THE STIMULANT EFFECT OF AMPHETAMINE

Effects of repeated intracerebroventricular microinjections of 18 nmol /10 mu l of neurotensin, [D-Tyr(11)]neurotensin, or saline were tested on motor activity in different groups of rats. One week after the fou rth central injection, sensitivity to the behavioral stimulant effect of amphetamine (1 mg/kg, i.p.) was tested. As previously reported, neu rotensin attenuated motor activity while [D-Tyr(11)]neurotensin when c ompared to saline produced an initial suppression followed by an excit ation. Despite such different behavioral effects, both peptides produc ed sensitization to the stimulant effect of amphetamine. These results show that repeated activation of neurotensin receptors produces long- lasting changes in responsiveness to a psychostimulant drug. (C) 1997 Elsevier Science B.V.