Neuroleptics remain the primary mode of treatment for Tourette's syndrome (TS). However, these drugs have profound side effects including dysphoria, cognitive deficits, and tardive dyskinesia. Recent randomized double- blind placebo-controlled clinical trials have shown that delta-9-tetrahdrocannabinol (THC) reduces symptoms of TS. These findings substantiate numerous anecdotal reports in the last several decades indicating that cannabis ameliorates some symptoms of TS and suggest that activation of cannabinoid neurotransmission is a plausible treatment strategy for treatment of TS. Treatment of TS with THC, however, is not a feasible option because of abuse-related concerns. Other pharmacological approaches that directly activate cannabinoid receptors in the brain are also problematic because the CB1 receptor, the primary cannabinoid receptor in the brain, becomes desensitized by direct exogenous agonist activation. Another foreseeable problem with targeting cannabinoid neurotransmission for treatment of TS is that this disorder is manifested during adolescence. Exposure to cannabis during this period has been linked to long-term adverse cognitive effects and increased propensity to develop other psychiatric disorders.
The aim of this proposal is to explore the feasibility of an alternative approach to enhance cannabinoid neurotransmission for treatment of TS which may not be associated with the aforementioned shortcomings. The approach involves manipulating levels of endogenous cannabinoids (eCB) anandemide and 2-AG by either reducing their hydrolysis or rate of uptake. Several brain permeable compounds have been recently described as effective pharmacological tools for blocking eCB transporter and anandamide hydrolysis. We propose to (1) explore the effectiveness of these agents in reversing tic-like behaviors in several animal models of TS in both adult and adolescent rats and, (2) determine the effect of repeated exposure to these compounds in early adolescent rats on cognitive and affective functioning in late adolescent and adult rats. It is anticipated that the results of these studies will, in addition to exploring the feasibly of a novel treatment approach for TS, provide the basis for future mechanistic studies on the role of eCB in regulating motor and cognitive functions during normal development and in disease states. Relevance to public health: Drugs used presently to treat Tourette's syndrome are minimally effective or have profound side effects. This preclinical proposal aims to complete exploratory studies to determine the feasibility and safety of a novel treatment option for this childhood neuropsychiatric disorder.
