Anti-aggressive effect elicited by coca-paste in isolation-induced aggression of male rats: influence of accumbal dopamine and cortical serotonin.

Coca-paste (CP), an illicit drug of abuse, has been frequently associated with aggressive and impulsive behaviors in humans. However, preclinical studies have not been carried out in order to characterize CP effects on aggression. The acute effect of CP, cocaine and caffeine (the main adulterant present in seized samples) on aggression was assessed using the isolation-induced aggression paradigm in male rats. The dopaminergic (DA) neurotransmission in the nucleus accumbens (NAcc) and serotonergic (5-HT) activity in the frontal cortex were explored. CP and cocaine induced a similar anti-aggressive effect on isolated rats although CP-treated animals showed a shorter latency to the first attack. Aggressive behavior was not increased per se by caffeine. Social investigation time was slightly reduced only by cocaine while exploratory activity and time spent walking were increased by the three drugs. Accumbal DA levels were significantly augmented by CP, cocaine and caffeine, although differences in DOPAC and HVA levels were evidenced. A decrease in DA turnover was only observed after CP and cocaine administration. Increased cortical 5-HT levels with a concomitant decrease in 5-HT turnover were observed after CP and cocaine whereas caffeine did not alter it. As cocaine but not caffeine reduced aggression, it seems like cocaine content was mainly responsible for CP anti-aggressive action; however, the presence of caffeine in CP may have a role in the shorter latency to attack compared to cocaine. Despite the increase in NAcc DA, the enhancement of cortical 5-HT levels can likely underlie the anti-aggression observed in CP-treated animals.