Decreased nitric oxide levels in the hippocampus may play a role in learning and memory deficits in ovariectomized rats treated by a high dose of estradiol

Abstract

The effects of a high estradiol dose on memory and on nitric oxide metabolites in hippocampal tissues were investigated. Sham-Est and OVX-Est Groups were treated with 4 mg/kg of estradiol valerate for 12 weeks. Time latency and path length were significantly higher in the Sham-Est and OVX-Est Groups than in the Sham and OVX Groups, respectively (p<0.001). The animals in the Sham-Est and OVX-Est Groups spent lower time in the target quadrant (Q1) than those of the Sham and OVX Groups during the probe trial test (p<0.05 and <0.001, respectively). Significantly lower nitric oxide metabolite levels in the hippocampi of the Sham-Est and OVX-Est Groups were observed than in the Sham and OVX ones (p<0.001). These results suggest that decreased nitric oxide levels in the hippocampus may play a role in the learning and memory deficits observed after treatment with a high dose of estradiol, although the precise underlying mechanisms remain to be elucidated.

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“…NO metabolites (NO 2 /NO 3 ) were measured according to the Griess reagent methods. In brief, after adding 100 μl supernatant to the Griess reagent, contents were transferred to a 96-well flat-bottomed micro-plate and absorbance was read at 520 nm using a micro-plate reader, and the final values were calculated from standard calibration plots [27][28][29].…”

Lipopolysaccharide-induced memory impairment in rats is preventable using 7-nitroindazole

“…The contents were then vortex-mixed and centrifuged, and the supernatants were transferred to a 96-well flat-bottomed microplate. Absorbance was read at 520 nm using a microplate reader, and the final values were calculated from standard calibration plots 19,20 .…”

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

“…[41] In contrast to these findings, it was shown that chronic treatment of female rats with high doses of esradiol has deleterious effects on learning and memory. [36] The results of the present study showed that the female rats with preposterous phase had a better performance in MWM compared with OVX rats. The results of passive avoidance test also showed that learning and memory procedures in animals with proestrus phase were better than OVX ones.…”

“…[1931323334] Learning and memory impairments, which have been reported in OVX rats confirm the beneficial effects of endogenous estradiol on learning and memory. [353637] The results of previous studies also indicated that estrogen therapy in OVX rats improves spatial learning and memory. [2238] Other researchers also showed that estrogen administration can reverse the effects of ovariectomy on avoidance and spatial memory.…”