Absence of Ketamine Effects on Learning & Memory Following Exposure during Early Adolescence: A Preliminary Report

Ketamine, traditionally used as a dissociative anesthetic and more recently studied as a fast-acting antidepressant and non-opiate pain treatment, is also used recreationally by adolescents. Using a rodent model, researchers exposed rats to ketamine or saline from early to mid-adolescence (postnatal days 22–40) and then, after a 50-day drug-free period, tested them in adulthood (starting at 90 days old) for general activity, spatial navigation, and nonspatial response learning. Contrary to predictions, the ketamine-exposed rats showed no spatial or nonspatial learning impairments compared to saline controls, though differences in general activity levels were observed. The findings suggest that the effects of adolescent ketamine exposure may depend on the specific developmental stage.

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Abstract

Traditionally, ketamine was considered useful as a dissociative anesthetic. More recently, ketamine has been examined for its effects as a fast-acting antidepressant, for treatment-resistant depression, and as a non-opiate treatment of chronic pain. Unfortunately, ketamine has enjoyed popularity as a recreational drug among both adolescents and young adults. While some research suggests the use of this drug during neurodevelopment is not without consequence, relatively little work has been conducted to examine the chronic effects of ketamine on the adolescent brain at different stages of neural development. Using a rodent model of development, we probed the effects of early adolescent exposure to ketamine. Between postnatal days 22 to 40, a period comprising early to mid-adolescence, rats were exposed to one of two doses of ketamine or saline. Beginning at 90 days of age and drug free for 50 days, a series of neuropsychological assessments were employed to examine general activity, spatial navigation, as well as nonspatial response learning. Contrary to prediction, except for differences in general activity levels, no spatial or nonspatial impairments were found among the drug- and saline-treated animals. The present results are considered in light of ketamine-associated effects found in a related study with older adolescent rats and the role of drug exposure during different points in adolescent brain development.