Locomotor sensitization to [d-Trp11]neurotensin after repeated injections of the dopamine uptake inhibitor GBR12783 in rats

Abstract Rats received one daily i.p. injection of the dopamine uptake inhibitor GBR12783 (1-[2-(diphenylmethoxy)ethyl]4-(3-phenyl-2-(propenyl)-piperazine) (10 mg/kg) or vehicle for 9 days. Fourteen days after discontinuing treatment, their locomotor activity was assessed after injection of GBR12783 (5 mg/kg) or vehicle, then 6 days later, after i.c.v. injection of [ d -Trp 11 ]neurotensin (750 ng) or saline. A sensitization to the stimulant locomotor effects of both GBR12783 and [ d -Trp 11 ]neurotensin occurred in rats exposed to the actimeter following the 1st., 5th and 9th injections of GBR12783. Rats without prior experience of the activity cages before the challenge tests showed no sensitization to either GBR12783 or [ d -Trp 11 ] neurotensin. Our data suggest that a similar mechanism may underlie the locomotor sensitization to GBR12783 and the heterosensitization to [ d -Trp 11 ]neurotensin.