Interaction between the endocannabinoid and serotonergic system in the exhibition of head twitch response in four mouse strains.
More than 10 % of children during school years suffer from a transient tic disorder, and 1 % has a particular type of tic disorder known as Tourette syndrome. At present, there is no available treatment that can improve tics without considerable side effects. Recent evidence indicates that tetrahydrocannabinol (THC), the principal psychoactive component of cannabis, reduced in mice the head twitch responses, a tic pharmacologically induced by the selective serotonin 5-HT2 receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI). THC has some considerable side effects that render its use problematic. In this view, cyclohexyl-carbamic acid 3-carbamoyl-biphenyl-3-yl ester (URB597), an indirect cannabinoid agonist that enhances endogenous anandamide levels, can constitute a valid alternative to the use of direct CB1 receptor agonists. We investigated whether URB597 may reduce the exhibition of DOI-induced head twitch responses in mice. Moreover, to address whether the effects of URB597 on DOI-induced behavioral response constitute a general phenomenon, we evaluated four (ABH, C57BL6N, SJLJ, CD-1) mouse strains. These strains have been selected in order to represent an ample spectrum of genetic background and phenotypic variation. Predictably, DOI induced consistent tic-like behaviors in all mice. While URB597 exerted slight sedation in C57BN6L mice, this cannabinoid agonist remarkably mitigated the exhibition of DOI-induced head twitch in all strains. Present data may disclose novel avenues for the pharmacological treatment of tic disorders.