Siomara da Cruz Monteiro

Vitamins E and C pretreatment prevents ovariectomy-induced memory deficits in water maze.

We investigated whether the pretreatment with vitamins E (alpha-tocopherol) and C (ascorbic acid) would act on ovariectomy-induced memory deficits in Morris water maze tasks. Adult female Wistar rats were divided into three groups: (1) naive (control), (2) sham (submitted to surgery without removal of ovaries) and (3) ovariectomized. Thirty days after surgery, they were trained in the Morris water maze in order to verify ovariectomy effects both on reference and working memory tasks. Results show that ovariectomized rats presented impairment in spatial navigation in the acquisition phase, as well as in the time spent in target quadrant and in the latency to cross over the location of the platform in test session, when compared to naive and sham groups (controls), in the reference memory task. Ovariectomy did not affect performance in the working memory task. Confirming our hypothesis, ovariectomized rats pretreated for 30 days with vitamins E and C had those impairments prevented. We conclude that ovariectomy significantly impairs spatial reference learning/memory and that pretreatment with vitamins E and C prevents such effect. Assuming this experimental memory impairment might mimic, at least in part, the cognitive deficit sometimes present in the human condition of lack of reproductive hormones, our findings lend support to a novel therapeutic strategy, based on vitamins E and C, to cognitive impairments in post-menopausal women.

In vivo and in vitro effects of homocysteine on Na+,K+-ATPase activity in parietal, prefrontal and cingulate cortex of young rats

In the present study we determined the effect of chronic administration of homocysteine on Na+,K+‐ATPase activity in synaptic membranes from parietal, prefrontal and cingulate cortex of young rats. We also studied the in vitro effect of homocysteine on this enzyme activity and on some oxidative stress parameters, namely thiobarbituric acid‐reactive substances (TBA‐RS) and total radical‐trapping antioxidant potential (TRAP) in the same cerebral structures. For the in vivo studies, we induced elevated levels of homocysteine in blood (500 μM), comparable to those of human homocystinuria, and in brain (60 nmol/g wet tissue) of young rats by injecting subcutaneously homocysteine (0.3–0.6 μmol/g of body weight) twice a day at 8 h intervals from the 6th to the 28th postpartum day. Controls received saline in the same volumes. Rats were killed 12 h after the last injection. Chronic administration of homocysteine significantly decreased (50%) Na+,K+‐ATPase activity in parietal, increased (36%) in prefrontal and did not alter in cingulate cortex of young rats. In vitro homocysteine decreased Na+,K+‐ATPase activity and TRAP and increased TBA‐RS in all cerebral structures studied. It is proposed that the alteration of Na+,K+‐ATPase and induction of oxidative stress by homocysteine in cerebral cortex may be one of the mechanisms related to the neuronal dysfunction observed in human homocystinuria.

α-Tocopherol and ascorbic acid prevent memory deficits provoked by chronic hyperprolinemia in rats

In the present study we investigated the action of alpha-tocopherol and ascorbic acid on the effects elicited by chronic hyperprolinemia on rat performance in the Morris water maze. Rats received subcutaneous injections of proline (experimental group) twice a day, with 10 h-interval, from the 6 to 28th days of age or an equivalent volume of 0.9% saline solution (controls). Half of the proline-treated group also received intraperitoneal administration of alpha-tocopherol (40 mg/kg) and of ascorbic acid (100 mg/kg) from the 6 to 28th days of life. On the 60th day of life, rats were subjected to testing in the water maze. Results show that chronic proline administration provokes impairment on spatial learning in reference memory task, as revealed by the increase of latency in acquisition, in the probe trial and in crossing over the platform location, as well as by the number of crossings, when compared to saline-treated animals. Proline-treated rats also demonstrated a reduced efficiency to find the platform position in the working memory task. Rats chronically treated with proline plus alpha-tocopherol and ascorbic acid had above effects prevented, suggesting the participation of oxidative stress in such effects. Our findings lend support to a novel therapeutic strategy, based on these vitamins, to the cognitive dysfunction associated with hyperprolinemia type II.

Ovariectomy increases Na+, K+-ATPase, acetylcholinesterase and catalase in rat hippocampus

In the present work we investigated the effect of ovariectomy on Na+, K+-ATPase and acetylcholinesterase (AChE) activities in rat hippocampus. We also studied some parameters of oxidative stress, namely total radical-trapping antioxidant potential (TRAP), thiobarbituric acid-reactive substances (TBA-RS), as well as the antioxidant enzyme activities superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities. Our hypothesis is that ovariectomy might cause alterations in essential enzyme activities necessary to brain normal functioning and that these chances could be caused by oxidative stress. Female adult Wistar rats were divided into three groups: (1) naive (control); (2) sham-operated; and (3) ovariectomized. Thirty days after ovariectomy rats were sacrificed. Results showed that rats subjected to ovariectomy presented a significant increase in Na+, K+-ATPase, AChE and CAT activities, but did not change the oxidative stress parameters studied when compared to sham or naive rats. Since ovariectomy mimics postmenopausal changes, our findings showing alteration in the activities of brain Na+, K+-ATPase, AChE and CAT may be related to problems in postmenopausal women.

Ovariectomy Enhances Acetylcholinesterase Activity But Does Not Alter Ganglioside Content in Cerebral Cortex of Female Adult Rats

In the present work we investigated the effect of ovariectomy on acetylcholinesterase (AChE) activity and ganglioside content in cerebral cortex of female rats. We also studied the activity of butyrylcholinesterase (BuChE) in serum of these animals. Adult Wistar rats were divided into three groups: (1) naive females (control), (2) sham-operated females and (3) castrated females (ovariectomy). Thirty days after ovariectomy, rats were sacrificed by decapitation without anaesthesia. Blood was collected and the serum used for BuChE determination. Cerebral cortex was homogenized to determine AChE activity and extracted with chlorophorm:methanol for ganglioside evaluation. Results showed that rats subjected to ovariectomy presented a significant increase of AChE activity, but did not change the content and the profile of gangliosides in cerebral cortex when compared to sham or naive rats. BuChE activity was decreased in serum of rats ovariectomized. Our findings suggest that the alteration in the activity of brain AChE, as well as serum BuChE activity caused by ovariectomy may contribute to the impaired cognition and/or other neurological dysfunction found in post-menopausal women.

Erratum to: Ovariectomy impairs spatial memory: prevention and reversal by a soy isoflavone diet

The 2nd paragraph in the “Animals and reagents” and the 1st paragraph in the “Experimental treatment” of the Material and Methods section (page 245) should be read as though combined in one paragraph. The following note should also be added: “Casein and soy isolated protein diets were prepared according to Franzon et al. (2005) and Reeves et al. (1993). Food intake and body weight were examined weekly. Both diets were isocaloric.” The full reference to the above is as follows: Franzon F, Chiarani F, Mendes RH, Bello-Klein A, Wyse ATS (2005) Dietary soy prevents brain Na,K-ATPase reduction in streptozotocin diabetic rats. Diabetes Res Clin Pract 69:107–112. Data included in Table 1 has raised debate and should not be considered with the paper. These corrections do not change the results and conclusions of the work.