Inactivation of the dorsal raphé nucleus reduces the anxiogenic response of rats running an alley for intravenous cocaine

► Cocaine has both positive (rewarding) and negative (anxiogenic) properties. ► Brain serotonergic (5-HT) systems have been implicated in the modulation of anxiety. ► Inactivation of the dorsal raphé nucleus reduced the anxiogenic response to cocaine. ► 5-HT is involved in the anxiogenic state produced by cocaine.