Phosphodiesterase inhibition by sildenafil citrate attenuates a maze learning impairment in rats induced by nitric oxide synthase inhibition.
Devan BD, Bowker JL, Duffy KB, Bharati IS, Jimenez M, Sierra-Mercado D, Nelson CM, Spangler EL, Ingram DK. Phosphodiesterase inhibition by sildenafil citrate attenuates a maze learning impairment in rats induced by nitric oxide synthase inhibition. Psychopharmacology (Berl). 2006 Jan; 183(4):439-45.