Protective Effect of L-Arginine against Oxidative Damage as a Possible Mechanism of its Bene.cial Properties on Spatial Learning in Ovariectomized Rats

Introduction: The role of ovarian hormones and nitric oxide (NO) on oxidative damage in brain tissues as well as learning and memory has been widely investigated.The present study was carried out to evaluate the effect of the precursor of NO, L-Arginine on learning and brain damage due to oxidative stress in ovariectomized (OVX) rats.Methods: Thirty -two rats were divided into four groups: 1) Sham, 2) OVX, 3) Sham-L-Arginine (Sham-LA) and 4) OVX-L-Arginine(OVX-LA).  The animals of sham- LA and OVX-LA were treated with 500 mg/kg of L-Arginine. The animals in Sham and OVX groups received 1 ml/kg saline. The animals were tested in Morris water maze and .nally, the brains were removed and MDA and total thiol concentrations were measured.Results: The escape latency and swimming path in OVX group were signi.cantly higher than in Sham group (p<0.01). The animals in OVX-LA group had signi.cantly lower swimming path length and escape latency compared to OVX group (p<0.01) while, there was no signi.cant difference between Sham- LA and Sham groups. In OVX-LA group, the brain tissues total thiol concentration was signi.cantly higher, and MDA concentration was lower than of OVX group (p<0.001).There was no signi.cant difference between Sham-LA and Sham groups. Discussion: It seems that the bene.cial properties of L-Arginine on spatial learning of ovariectomized rats are in part due to its protective capacity against oxidative damage

The effects of tamoxifen on learning, memory and brain tissues oxidative damage in ovariectomized and naïve female rats

Background: Regarding the modulatory effects of tamoxifen (TAM) on the actions of estrogen in the present study, the effects of TAM on learning, memory and brain tissues oxidative damage in ovariectomized (OVX) and naοve female rats was investigated. Materials and Methods: The animals were divided into: (1) Sham, (2) OVX, (3) Sham-tamoxifen (Sham-TAM) and (4) ovariectomized-tamoxifen (OVX-TAM). The animals of the Sham-TAM and OVX-TAM groups were treated by TAM (1 mg/kg; 4 weeks). Results : In Morris water maze, the escape latency in the OVX group was higher than in the Sham group (P < 0.01). The time latency in the animals of OVX-TAM group was lower than that of OVX group (P < 0.01); however, there were no significant differences between the Sham-TAM and Sham groups. In the probe trial, the time spent in target quadrant (Q 1 ) by the animals of OVX group was lower than that of Sham group (P < 0.01). Interestingly, the animals of OVX-TAM group spent more times in target quadrant (Q 1 ) compared with OVX group (P < 0.01). In passive avoidance test, the animals of OVX group had lower latencies to enter the dark compartment compared with the Sham group (P < 0.05). The time latency to enter the dark compartment by animals of OVX-TAM group was higher than in OVX group (P < 0.01). In OVX-TAM group, the total thiol concentration was significantly higher (P < 0.05) and malondialdehyde concentration was lower (P < 0.01) than OVX group. Conclusions: These results allow us to propose that TAM enhances learning and memory of OVX rats. The possible mechanism may be due to the protective effects against brain tissues oxidative damage

Tamoxifen antagonizes the effects of ovarian hormones to induce anxiety and depression-like behavior in rats

The effects of tamoxifen (TAM) on anxiety and depression-like behavior in ovariectomized (OVX) and naïve female rats were investigated. The animals were divided into Sham-TAM, OVX-TAM, Sham and OVX groups. Tamoxifen (1 mg/kg) was administered for 4 weeks. In the forced swimming test, the immobility times in the OVX and Sham-TAM groups were higher than in the Sham group. In the open field, the numbers of central crossings in the OVX and Sham-TAM groups were lower than the number in the Sham group, and the number of peripheral crossings in the OVX group was lower than the number in the Sham group. In the elevated plus maze, the numbers of entries to the open arm among the animals in the Sham-TAM and OVX groups were lower than the number in the Sham group, while the number of entries to the open arm in the OVX-TAM group was higher than the number in the OVX group. It was shown that deletion of ovarian hormones induced anxiety and depression-like behavior. Administration of tamoxifen in naïve rats led to anxiety and depression-like behavior that was comparable with the effects of ovarian hormone deletion. It can be suggested that tamoxifen antagonizes the effects of ovarian hormones. It also seems that tamoxifen has anxiolytic effects on ovariectomized rats

Protective Role of Endogenous Ovarian Hormones Against Learning and Memory Impairments and Brain Tissues Oxidative Damage Induced by Lipopolysaccharide

vi, 1184 hlm.; 21 cm