Chronic Treatment by L-NAME differently Affects Morris Water Maze Tasks in Ovariectomized and Naïve Female Rats

Introduction: The role of ovarian hormones and nitric oxide (NO) in learning and memory and their interaction has been widely investigated. The present study carried out to evaluate different effect of L-NAME on spatial learning and memory of ovariectomized (OVX) and sham operated rats. Methods: 32 rats were divided into 4 groups: 1) Sham; 2) OVX; 3) Sham-LN; and 4) OVX-LN. The animals of groups 3 and 4 were treated by L-NAME (10 mg/kg/ day) for 8 weeks while the animals of groups 1 and 2 received saline (1ml/kg/day) instead of L-NAME. The animals of all groups were then tested in Morris water maze during five days. The escape latency and traveled distance were compared between groups. Results: Distance and time in OVX group was significantly higher than Sham group (p 0.01 and p 0.05). Time and distance in Sham-LN group was higher in comparison with Sham group (p 0.05 and p 0.01). There were no significant differences between OVX-LN and OVX groups in escape latency and traveled distance. Discussion: The results of present study showed that removal of ovarian hormones could impair Morris water maze tskas includiong time and distance. Administarion of non specific nitricoxide inhibitor, L-NAME, affects Morrsi water maze tasks however, its effect is different in the absence and presence of ovarian hormones but it needs to be more investigated.