Sildenafil enhances locomotor activity in young mice and exerts anxiogenic effects in both young and aged mice

BACKGROUND: Sildenafil is a selective PDE5 inhibitor that increases cGMP levels in the target tissues and is an effective treatment agent for erectile dysfunction. The nitric oxide-cGMP pathway might be implicated in regulation of certain CNS functions, including locomotor activity and anxiety. MATERIAL/METHODS: The aim of the current study was to investigate effects of sildenafil (3 and 10 mg/kg) on anxiety and locomotor activity in open field and elevated plus maze (EPM) tests in young and aged mice. RESULTS: Sildenafil (3 and 10 mg/kg) significantly decreased the percent of time spent in the open arms compared to the control group in young animals in the EPM test, but only the 10 mg/kg dose significantly decreased the percentage of total number of entries to the open arms in young animals. Sildenafil (3 and 10 mg/kg) significantly decreased the percentage of total number of entries to the open arms in aged animals in the EPM test, but it significantly increased total distance moved and speed of the animals in the locomotor activity test in young animals. The total distance moved and the speed of the animals significantly decreased in aged animals compared to the young control group, although sildenafil (3 and 10 mg/kg) did not alter these parameters in aged mice. CONCLUSIONS: Our results show that sildenafil had anxiogenic effects in young as well as aged mice, but it enhanced locomotor activity only in the young mice in the EPM test. Thus, sildenafil seems to exert different effects on anxiety and locomotion in young and aged animals.