LAMOTRIGINE HAS NO ANTIPARKINSONIAN ACTIVITY IN RAT MODELS OF PARKINSONS-DISEASE

In rodent models of Parkinson's disease such as reserpinized or 6-hydr oxydopamine substantia nigra lesioned rats, blockade of glutamate rece ptors of the NMDA (N-methyl-D-aspartate) or the AMPA ha-amino-3-hydrox y-5-methyl-4-isoxazolepropionate) receptor subtypes and concomitant tr eatment with L-DOPA (L-3,4-dihydroxyphenylalanine) or direct dopamine agonists restores locomotor activity and induces rotations. An alterna tive approach to interfere with glutamatergic transmission would invol ve the inhibition of glutamate release resulting in functional glutama te antagonism. The novel antiepileptic drug lamotrigine blocks the ver atridine-evoked release of the excitatory transmitters L-glutamate and L-aspartate. Due to its presumed antiglutamatergic action it has been suggested that lamotrigine may be useful in the treatment of Parkinso n's disease. In a preliminary open-label study in patients with Parkin son's disease some favourable effects were reported. The present study was undertaken to systematically investigate the effects of lamotrigi ne in rat models of Parkinson's disease. However, lamotrigine failed t o exert antiparkinsonian activity in reserpinized rats when administer ed alone or in combination with the dopamine receptor agonist apomorph ine. In rats bearing 6-hydroxydopamine lesions of the substantia nigra lamotrigine did not induce rotations when given alone and did not mod ify rotations induced by apomorphine or the preferential dopamine D-2 receptor agonist lisuride. On the basis of these negative results it i s predicted that lamotrigine will not have significant favourable effe cts on akinesia and rigidity in Parkinson's disease patients.