Modification of Serial Pattern Learning by Designer Tryptamine Exposure during Adolescence: Comparison with Damage to the Dorsal Hippocampus or Prefrontal Cortex

Recreational use of the club drug 5-MeO-DIPT (Foxy) has increased, but its neurobiological effects are poorly understood. In this animal study, adolescent rats received repeated injections of 10 mg/kg of 5-MeO-DIPT, MDMA, or saline. As adults, they were trained for 30 days on a nonmonotonic serial learning task involving food pellets. Control rats distinguished among the series elements, but tracking performance in both drug-treated groups improved with training yet after 30 days was not markedly different from that of rats with hippocampal or prefrontal cortex lesions. The findings suggest that compromised serotoninergic systems from adolescent drug exposure impair cognitive processes in appetitive serial learning.

Study at a glance

Abstract

Fo xy or Methoxy Fo xy (5-MeO-DIPT) is one of a series of new "club drugs" that within the past decade has gained in popularity among recreational users as an alternative to MDMA (Ecstasy). Unlike M DMA, not much is known about the neurobiological consequences of 5-MeO-DIPT use. Little is known about the effects of either co mpound on learning in a nonspatial appetitive task. In the present study, adolescent rats were given repeated injections of 10 mg/kg of 5-MeO-DIPT, MDMA, or a corresponding volume of isotonic saline. In serial learning tasks, depending on task demands, there is a gro wing body of evidence suggesting that multip le memo ry systems play a critical role, with each system playing a more o r less dominant role depending on the available stimu li and task demands. Therefore, for co mparison purposes, the drug-treated rats were co mpared with that of h ippocampus- or prefrontal cortex-lesioned rats. After adolescent drug exposure or lesions during adolescence, adult animals were trained All animals were trained for 30 days on a three-element, nonmonotonic pattern consisting of 21, 0, and 7 food pellets, respectively. Control rats were capable of d istinguishing among the elements of the series, as indexed by running times. As expected, the tracking performance of the lesioned rats was impaired. Performance in both the 5-MeO-DIPT- and the MDMA-treated rats improved with training but after 30 days was not markedly d ifferent than the lesioned animals. The results are discussed in terms of measured alterat ions in serotonin activity in the fo rebrain and the consequences of compro mised serotoninergic systems on the cognitive processes involved in appetitive serial learning tasks.