Neurobehavioral effects of anandamide and cannabinoid receptor gene expression in mice.

The objective of the present study was to determine the neurobehavioral effects of the putative endogenous cannabinoid ligand, anandamide, and its influence on cannabinoid (CB1) receptor gene expression. The effect of acute administration of anandamide to C57BL/6, DBA/2, and ICR mice were evaluated in motor function and emotionality tests. The C57BL/6 and ICR mouse strains were more sensitive than the DBA/2 strain to the depression of locomotor activity and stereotyped behavior caused by anandamide. Although anandamide produced catalepsy in all three strains, anandamide induced ataxia in the minus-maze test only in the C57BL/6 animals and only at the lowest dose used. In the plus-maze test system, anandamide produced a mild aversive response, and by the third day of treatment the mouse strains developed an intense aversion to the open arms of the plus-maze. Northern analysis data using the recently cloned mouse cannabinoid receptor cDNA as a probe indicated that there was abundant expression of CB1 gene in the whole brain of the ICR mouse than in the brains of the C57BL/6 and DBA/2 strains with or without pretreatment with anandamide. The anandamide induced neurobehavioral profile does not seem to correspond to the CB1 gene expression in the mouse strains. It is, therefore, unlikely that the CB1 receptor mediates all the cannabinomimetic effects of anandamide in the brain.