The role of serotonin (5-HT) in expression of conflict behavior in rodents has already been postulated. Conflict behavior is reported to increase 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) levels in the raphe nuclei and limbic forebrain. Administration of p-chlorophenylalanine (p-CPA, a 5-HT synthesis inhibitor) is known to cause anticonflict effect in some animals models of anxiety. This phenomenon has been confirmed in the present experiment by evaluating rat behavior in the Vogel conflict test (VT) of punished drinking. The effect observed in the VT correlated significantly with 5-HT and 5-HIAA concentration decrease in the brain stem, hippocampus and frontal cortex. VT appeared also very sensitive to the anticonflict action of GABA A -benzodiazepine receptor complex agonists. Benzodiazepines (BDZ) are known to exert inhibitory influence on 5-HT neurotransmission. These facts indicated that disinhibition of conflict behavior in the VT after BDZ may depend on changes in the activity of central 5-HT system. Accordingly, in autoradiographic studies serotonin depletion after neurotransmitter synthesis inhibition was followed by a significant decrease in [ 3 H]muscimol binding in the limbic forebrain structures. This could reflect some adaptive processes in the activity of the GABA A -benzodiazepine receptor complex, secondary to disinhibition of GABAergic nerotransmission. It was also shown that intra-hippocampal injections of midazolam, a full nonselective BDZ receptor agonist, significantly increased punished consumption of water in the VT in the p-CPA pretreated animals, at the dose which did not produce any effect by itself (10 μg/site). Moreover, the anticonflict influence of p-CPA was no longer present after intrahippocampal injections of picrotoxin (a GABA A -BDZ receptor complex antagonist) at the dose 0.1 μg/site. It is concluded that anticonflict effect of 5-HT depletion is under control of GABAergic innervation of the hippocampus. The data indicate antagonistic interaction between GABA and 5-HT systems regulating rat emotional behavior.