Effects of 3,4-methylenedioxymethamphetamine on neural activity in the nucleus accumbens of male mice engaged in social behavior.

3,4-methylenedioxymethamphetamine (MDMA), a commonly abused recreational drug, induces prosocial effects such as increased sociability and empathy. The nucleus accumbens (NAc) has been suggested to play a crucial role in these MDMA-mediated prosocial effects. However, the relationship between social behavior and NAc neural activity, and the effects of MDMA on this relationship, remain unknown. In this study, we measured NAc neural activity using fiber photometry and classified the behaviors of mice at times of transient increases in NAc neural activity during the social approach test (SAT). We found that NAc neural activity transiently increased at the onset of turning toward and sniffing novel mice during the SAT, although the frequency of turning was relatively low. We then examined the effects of MDMA on behavior and NAc neural activity and found that MDMA decreased the duration of sniffing per bout but did not alter NAc neural activity at the onset of turning toward or sniffing novel mice. These results suggest that MDMA does not affect the transient increase in NAc neural activity at the onset of social behaviors.