Pakartotinio poveikio amfetaminu ir morfinu tiesioginiai ir sąlygoti efektai žiurkių 50-kHz ultragarso artikuliacijoms

The aim and objectives. The purpose of this study was to evaluate the effects of a repeated treatment with either amphetamine or morphine on the emission of 50-kHz ultrasonic vocalizations (USVs) by male rats. 50-kHz USVs were evaluated both after drug administration (direct effect) and after rats’ re-exposure to the environment where they previously received the drug (conditioned effects). This study also evaluated the extinction of conditioned USVs. In the present study, the administrations of amphetamine and morphine were performed on either consecutive or alternate days, in order to evaluate the role of the protocol of administration on the effects of these drugs. Furthermore, the present study evaluated the modifications in both the direct and conditioned “trill” USVs, that have been proposed to be specifically emitted in response to rewarding stimuli, to understand the importance of this USVs subtype in the study of the effects of substances of abuse. Materials and methods. Male rats were used in this study. Distinct groups of rats were treated with either amphetamine or morphine, and each rat received only one substance. Rats treated with vehicle (purified water) were used as controls. Vocalizations were registered with microphones for ultrasounds. All the recorded vocalizations were collected with a computer and analyzed using a suited software for sonographic analysis. Statistical analysis was performed with the software Statistica for Windows. Results. Direct effects: rats treated with amphetamine in consecutive and in intermittent manner have shown a significant emission of 50-kHz USVs while rats treated with morphine have not. Conditioned effects: re-exposure of rats to the test cage, which was associated with the administration of the substances of abuse, provoked a significant emission of 50-kHz USVs in rats treated with either amphetamine or morphine. The emission of conditioned 50-kHz USVs following the re-exposure to the test cage 7 days after repeated treatment discontinuation was stronger in rats treated on alternate days. Practical recommendations. This study suggests that evaluating modifications in the emission of 50-kHz USVs can be a useful rat model to evaluate the expectation towards substances of abuse. The emission of 50-kHz USVs could be used to implement new experimental models to study the psychological component of drug dependence