ANHEDONIA IN A RAT MODEL OF TREATMENT-RESISTANT DEPRESSION: INSIGHTS FROM ULTRASONIC VOCALIZATIONS AND RELATED BEHAVIORAL MEASURES

The Wistar-Kyoto rat strain is a model for treatment-resistant depression, exhibiting behaviors indicative of anhedonia. Although anhedonia is measured using the sucrose preference test, 50-kHz ultrasonic vocalizations (USVs) hold promise as a complementary assessment tool. This study aimed to detect whether 50-kHz USVs differ in the Wistar-Kyoto rats compared to control Wistar rats. First, Wistar-Kyoto and Wistar rats were compared for their basal 50-kHz calls. Then, rats were repeatedly treated with four administrations of either amphetamine or morphine, and 50-kHz calls were recorded. In addition, the drug-evoked locomotor activity, sucrose consumption in the sucrose preference test, and the time spent in the drug- vs. saline-paired compartment in the conditioned place preference test were collected. Wistar-Kyoto rats emitted fewer basal calls and fewer calls following the first and the fourth amphetamine administration. Contrary to controls, amphetamine did not affect the number of calls in Wistar-Kyoto rats following the first administration. Wistar-Kyoto rats also displayed reduced amphetamine-induced locomotor activity and sucrose consumption in the sucrose preference test. Morphine did not affect USVs or locomotion in either strain. The results highlight the benefits of 50-kHz calls as a complementary behavioral marker for assessing anhedonia in preclinical models of depression.