AGGRESSIVE-BEHAVIOR AND JAMMING AVOIDANCE-RESPONSE IN THE WEAKLY ELECTRIC FISH GYMNOTUS-CARAPO - EFFECTS OF 3,4-METHYLENEDIOXYMETHAMPHETAMINE (MDMA)

Jamming avoidance response (JAR) and aggressive behavior were evaluate d in pairs of weakly electric fish Gymnotus carapo. JAR consists of br ief frequency increases of the electric organ discharge (EOD) of the f aster fish of the pair when a coincidence between the EODs is close to occur. Aggressive behavior is known to be very strong and robust in t his species. 3,4-Methylenedioxymethamphetamine (MDMA) treatment signif icantly decreased the intensity of aggressive behavior while it increa ses the intensity and probability of occurrence of JAR. After MDMA tre atment, the aggressive behavior was replaced by a distinct nonaggressi ve (''friendly'') type of interaction. In addition to JAR, other behav iors, such as novelty response to visual stimuli, were enhanced with M DMA treatment, suggesting that the effects of this drug on aggressive behavior were not due to a general depression of all behavioral displa ys. Comparative aspects of the described behavioral changes with the e ffects of MDMA in humans are discussed. (C) 1997 Elsevier Science Inc.