Impact of cannabinoid CB2 receptor activity on aggressive behavior in mice and sensitization to methamphetamine antiaggresive effects. Cannabinoid receptor CB2 is localized mainly outside of the CNS. Thus a poor impact of its activity on behavior can be expected. Previously we found development of both sensitization to methamphetamine (MET) antiaggressive effects by pre-treatment with repeated MET doses and a cross-sensitization to this MET effect with cannabinoid CB1 receptor agonist methanandamide in the model of agonistic behaviour in singly-housed male mice on paired interactions with non-aggressive group-housed partners. This supported the evidence of interaction between the endocannabinoid system and MET brain mechanism. The aim of the present study was to investigate whether the CB2 receptor activity might also be involved in regulation of mouse agonistic behaviour, and in development of sensitivity to methamphetamine. Therefore the CB2 receptor agonist JWH 015 (JWH) has been tested using identical experimental design as previously with CB1 receptor agonist. JWH given to aggressive singly-housed mice at the doses of 0.1, 1.0 and 10.0 mg/kg, intraperitoneally, 15 min prior to observation, inhibited the occurrence of aggressive activities; significantly of tail rattling and threat after the highest dose. Significant behavioral sensitization to MET anti-aggressive effects was apparent after the pre-treatment with 5 MET doses of 1 mg/kg/day and administration of the "challenge dose" of 1 mg/kg after 5 days of withdrawal. The pretreatment with JWH (5 daily doses of 1.0 mg/kg) however did not produce the cross-sensitization to MET "challenge dose". Just the stimulation of locomotion (walking) was registered on a higher level of significance in JWH 015 sensitized mice comparing to saline sensitized group. Thus, the all results obtained in the present study suggest that CB2 receptor system is not very important for interaction of endocannabinoid system and brain processes involved in sensitization to metamphetamine.