Possible involvement of nitric oxide (NO) in anxiety-like behavior induced by female steroid hormones

I ntrodu ct io n , Nitric oxide (NO) is a neurornodulator and an intercellular messenger th at mediate several functio ns in the eNS. Possible involvement of NO in anxiety like behavior induced by ovarian hormones was studied in ovarec tornizcd female rats. Materials and Methods. 12 gro ups of rats were ovarectomized bilateraly and 14 days after surgery they received estradiol ben zoat (10 [.Lg/kg, sc) and or progesterone (25 mg/kg, sc) or corn oil (0.2 ml/rat , sc) and L-Name (60 mg/kg,i.p) or L-Aarginine (100 mg/kg,i.p) or normal saline (0.5 rnl/rat, i.p ). The behavior al te sts began 6 hours after pro gesterone and 3 hours after estradiol administera tion. Behavioural test consi sted measurment of exploratory activities on elev ated plus maze test. Results. There was incre ased exploration of open arms under pro gesterone administe rat icn alone or with L-Name, and decreased und er estradio l administeration alone or with L-Arg inine. The anxiolytic-like effect of progesterone abolished when L-Arginine administerated, and anxiogenic-like effect of estradiol was inhibited when L-Name injected. Conclusio n . These data indicate involvement of NO in the mediation of the effect s of ovarian steroid hormones on anxiety process