title: Chronic treatment with the nitric oxide synthase inhibitor, L-NAME, attenuates estradiol-mediated improvement of learning and memory in ovariectomized rats.
abstract: BACKGROUND
  The role of ovarian hormones and nitric oxide in learning and memory has been widely investigated.
  
  
  OBJECTIVE
  The present study was carried out to evaluate the effect of the nitric oxide synthase (NOS) inhibitor, N (G)-nitro-L-arginine methyl ester (L-NAME), on the ability of estradiol to improve learning in OVX rats using the Morris water maze.
  
  
  METHODS
  Forty rats were divided into five groups: (1) ovariectomized (OVX), (2) ovariectomized-estradiol (OVX-Est), (3) ovariectomized-L-NAME 10 (OVX-LN 10), (4) ovariectomized-L-NAME 50 (OVX-LN 50) and (5) ovariectomized-estradiol-L-NAME 50 (OVX-Est-LN 50). The animals in the OVX-Est group were treated with a weekly injection of estradiol valerate (2 mg/kg; i.m.). The OVX-LN 10 and OVX-LN 50 groups were treated with daily injections of 10 and 50 mg/kg L-NAME (i.p.), respectively. The animals in the OVX-Est-LN 50 group received a weekly injection of estradiol valerate and a daily injection of 50 mg/kg L-NAME. After 8 weeks, all animals were tested in the Morris water maze.
  
  
  RESULTS
  The animals in the OVX-Est group had a significantly lower latency in the maze than the OVX group (p<0.001). There was no significant difference in latency between the OVX-LN 10 and OVX-LN 50 groups in comparison with the OVX group. The latency in the OVX-Est-LN 50 group was significantly higher than that in the OVX-Est group (p<0.001).
  
  
  CONCLUSIONS
  These results show that L-NAME treatment attenuated estradiol-mediated enhancement of spatial learning and memory in OVX rats, but it had no significant effect in OVX rats without estrogen, suggesting an interaction of nitric oxide and estradiol in these specific brain functions.
authors.affiliation: Dept. of Biology, Faculty of Basic Science, Islamic Azad University, Khuraskan Branch, Isfahan, Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Azizi-Malekabadi
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Hosseini
authors.forename: Fatima
authors.initials: F
authors.lastname: Saffarzadeh
authors.forename: Reza
authors.initials: R
authors.lastname: Karami
authors.forename: Fatimeh
authors.initials: F
authors.lastname: Khodabandehloo
mesh_terms: D000818:Animals; D004338:Drug Combinations; D004359:Drug Therapy, Combination / Q000009:adverse effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D018782:Maze Learning / Q000187:drug effects*; D008568:Memory / Q000187:drug effects*; D023421:Models, Animal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009277:Nandrolone / Q000031:analogs & derivatives* / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010052:Ovariectomy; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D013037:Spatial Behavior / Q000187:drug effects
chemical_list: D004338:Drug Combinations; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D004967:Estrogens; C454300:estradiol valerate-dienogest; D004958:Estradiol; D009277:Nandrolone; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester