Adenosine A2A receptor antagonism increases nNOS-immunoreactive neurons in the striatum of Huntington transgenic mice.

Medium spiny GABAergic projection neurons are progressively lost in Huntington's disease (HD), whereas there is preferential sparing of the few interneurons co-expressing NPY, somatostatin and neuronal nitric oxide synthase. We investigated the effect of the selective adenosine A(2A) receptor antagonist SCH58261 (0.01 mg/kg, acutely and chronically administered i.p.) on nNOS striatal expression and motor impairment in R6/2 transgenic mice in clearly symptomatic phase (10-11-week old). SCH58261 chronically administered increased the number of nNOS-immunoreactive neurons (nNOS-IR) in the striatum of R6/2 mice. No glial activation was detected in the striatum or cortex. SCH58261 also improved walking in the inclined plane test but not motor capability evaluated by the rotarod test. These findings demonstrate for the first time a role of adenosine A(2A) receptors in regulating nNOS expression in the striatum. We suggest that the protective effect of A(2A) antagonism in HD is related to the increase in striatal nNOS-IR neurons.