Hypocretin receptor 1 blockade early in abstinence prevents incubation of cocaine seeking and normalizes dopamine transmission

Abstract

Abstinence from cocaine use has been shown to elicit a progressive intensification or incubation of cocaine craving/seeking that is posited to increase the likelihood of relapse. While the mechanisms underlying incubation of cocaine seeking remain elusive, considerable evidence suggests that abstinence from cocaine promotes mesolimbic dopamine adaptations that contribute to exaggerated cocaine seeking. Consequently, preventing these dopamine adaptations may reduce incubation of cocaine seeking and thereby decrease the likelihood of relapse. In the present studies, we first examined the relationship between incubation of cocaine seeking and dopamine transmission in the nucleus accumbens following abstinence from intermittent access to cocaine. Given the extensive evidence that hypocretins/orexins regulate motivation for cocaine, we then examined to what extent an intraperitoneal injection of a hypocretin receptor 1 antagonist on the first day of abstinence would prevent incubation of cocaine seeking and dopamine adaptations later in abstinence. Results indicated that abstinence from intermittent access to cocaine engendered robust incubation of cocaine seeking in both female and male rats. We also observed aberrant dopamine transmission, but only in rats that displayed incubation of cocaine seeking. Further, we showed that a single injection of the hypocretin receptor 1 antagonist, RTIOX-276, on the first day of abstinence prevented incubation of cocaine seeking and aberrant dopamine transmission. These findings suggest that hypocretin receptor 1 antagonism may serve as a viable therapeutic for reducing cocaine craving/seeking early in abstinence, thus reducing the likelihood of relapse.