The neuronal KCNQ channel opener retigabine inhibits locomotor activity and reduces forebrain excitatory responses to the psychostimulants cocaine, methylphenidate and phencyclidine

Abstract

Many central stimulating drugs have a pronounced stimulatory effect on striatal and cortical activity which is associated to enhanced function of mesencephalic dopaminergic neurons. Mesencephalic KCNQ (also termed K v7) potassium channels suppress the basal activity of dopaminergic neurons in the substantia nigra and ventral tegmental area. These regions have extensive dopaminergic projections to the striatum and cortex, and positive modulation of KCNQ channel function may therefore potentially reduce the reinforcing impact of central stimulating drugs. We studied the effects of the principal neuronal KCNQ channel opener, retigabine, in rats exposed acutely to cocaine, methylphenidate (dopamine reuptake inhibitors) or phencyclidine (PCP, a psychotomimetic NMDA receptor antagonist). Retigabine (≥ 1.0 mg/kg) inhibited cocaine, methylphenidate and PCP-stimulated locomotor activity. Also, retigabine reduced spontaneous locomotor activity. The inhibitory effect of retigabine on psychostimulant-induced locomotor activity was accompanied by a marked reduction in c-Fos expression, in particular the nucleus accumbens and primary motor cortex were responsive to retigabine pre-treatment. Notably, retigabine also reduced basal extracellular levels of striatal dopamine metabolites and partially prevented dopamine overflow in the striatum induced by dopamine reuptake blockade. In combination, these data suggest that retigabine reduces striatal and cortical excitability, thereby attenuating excitatory effects of central stimulating drugs in dopamine-rich areas of the rat forebrain. KCNQ channel openers may therefore be of potential relevance in the treatment of addiction states caused by abuse of psychostimulants.