The partial α2,3,5 GABAA receptor agonist, L-838,417 has been reported to have anxiolytic effects in adult rodents. Although maturational differences exist for the GABAA receptor subunits, the anxiolytic effects of L-838,417 have not been tested in younger animals. The goal of the present experiments was to determine whether L-838,417 reverses anxiety-like behavior induced by either an unfamiliar environment (Experiment 1) or repeated restraint stress (Experiment 2) differentially in adolescent and adult, male and female Sprague–Dawley rats using a modified social interaction test. In Experiment 1, rats were injected with 0, 0.5, 1.0, 2.0, or 4.0mg/kg L-838,417, i.p. and tested 30min later in an unfamiliar test context for 10min. In Experiment 2, rats were exposed to restraint stress (90min daily for 5days). Immediately after the last restraint session, animals were injected with L-838,417 and placed alone for 30min in the test apparatus to familiarize them to this context prior to the 10min social interaction test. In Experiment 1, L-838,417 produced anxiolytic effects in adults at 1.0mg/kg, as indexed by a transformation of social avoidance into preference and an increase in social investigation. In adolescents, a dose of 2.0mg/kg eliminated social avoidance, but had no anxiolytic effects on social investigation. Testing under familiar circumstances (Experiment 2) after repeated restraint stress eliminated age differences in sensitivity to L-838,417, with 0.5mg/kg reversing the anxiogenic effects of prior stress regardless of age, but with doses≥1 mg/kg decreasing social investigation, an effect possibly due in part to locomotor-impairing effects of this compound. Although locomotor activity was suppressed in both experiments, higher doses of L-838,417 were necessary to suppress locomotor activity in Experiment 1. Thus, anxiolytic effects of L-838,417 were found to be context-, age-, and stress-dependent.
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