Involvement of cannabinoid CB1 and CB2 receptor activity in the development of behavioural sensitization to methamphetamine effects in mice.

OBJECTIVES

An increased behavioural response ("behavioural sensitization") to drugs of abuse occurs after repeated treatment. In the present study the possibility of cross-sensitization existence between various cannabinoid receptor ligands--CB1 agonist methanandamide, CB2 agonist JWH 015, and CB1 antagonist AM 251 with methamphetamine was explored.

METHODS

Locomotion in the open field was measured in naive mice and in those pre-treated acutely and repeatedly (for 8 days), respectively, with either vehicle or tested drugs.

RESULTS

Methamphetamine produced significant sensitization to its stimulatory effect on locomotion. Methanandamide pre-treatment elicited cross-sensitization to methamphetamine effect, whereas pre-treatment with JWH 015 did not. Combined pre-treatment with methamphetamine+AM 251 suppressed sensitization to methamphetamine.

CONCLUSIONS

These results suggest that the activity of the endocannabinoid system is involved in the neuronal circuitry underlying the development of sensitization to methamphetamine.