Therapeutic effects of Δ9-THC and modafinil in a marmoset Parkinson model

Current therapies for Parkinson's disease (PD) like l-dopa and dopamine (DA) agonists have declined efficacy after long term use. Therefore, research towards supplementary or alternative medication is needed. The implementation in PD can be expedited by application of compounds already used in the clinic. In this study the therapeutic effects of the psychoactive compounds Δ9-tetrahydrocannabinol (Δ9-THC) and modafinil were tested in the 1-methyl-1,2,3,6-tetrahydropyridine (MPTP)–marmoset model for PD.The anti-parkinson effects of Δ9-THC (4 mg/kg) and modafinil (100 mg/kg) in parkinsonian marmosets were assessed with two behavioral rating scales covering parkinsonian symptoms and involuntary movements and two test systems assessing the locomotor activity and hand–eye coordination.Δ9-THC improved activity and hand–eye coordination, but induced compound-related side-effects. Modafinil improved activity and observed parkinsonian symptoms but not hand–eye coordination. It can be concluded that both compounds have therapeutic values and could supplement existing therapies for PD.