Nicotinamide treatment reduces the levels of oxidative stress, apoptosis, and PARP-1 activity in Aβ(1-42)-induced rat model of Alzheimer's disease

The underlying mechanisms of Alzheimer's Disease (AD) are still unclear. It is suggested that poly(ADP-ribose) polymerase-1 (PARP-1) overactivation can cause neuroinflammation and cell death. In this study we searched the effects of nicotinamide (NA), endogenous PARP-1 inhibitor, on oxidative stress, apoptosis, and the regulation of PARP-1 and nuclear factor kappa B (NF-κB) in amyloid beta peptide (1-42) (Aβ(1-42))-induced neurodegeneration. Sprague-Dawley rats were divided into four groups as control, Aβ(1-42), Aβ(1-42) + NA(100 and 500 mg/kg). All groups were stereotaxically injected bilaterally into the hippocampus with Aβ(1-42) or saline. After surgery NA administrations were made intraperitoneally (ip) for 7 days. In order to investigate the effects of Aβ(1-42) and NA, protein carbonyls, lipid peroxidation, reactive oxygen species (ROS) production, glutathione (GSH) levels, activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), mitochondrial function, mRNA and protein levels of PARP-1, NF-κB, p53, Bax, and Bcl-2 were measured in specific brain regions such as cortex and hippocampus. Aβ(1-42) treatment only increased the oxidative stress parameters and caused decline in antioxidant enzyme activities, mitochondrial function, and GSH levels. Also, overexpression of PARP-1, NF-κB, p53, Bax, and the decreased levels of Bcl-2 were observed in Aβ(1-42)-treated group. NA treatments against Aβ(1-42)-upregulated Bcl-2 and downregulated PARP-1, NF-κB, p53, and Bax levels. NA treatments also decreased the oxidative stress parameters and elevated antioxidant enzyme activities, GSH levels, and mitochondrial function against Aβ(1-42) treatment. These data suggest that NA may have a therapeutic potential in neurodegenerative processes due to the decreased levels of oxidative stress, apoptosis, and PARP-1 activity.

Sexually dimorphic cognitive style in rats emerges after puberty

In a water maze (WM), rats employ different and sexually dimorphic behavioral strategies to solve a place-learning task, a test of cognitive/propositional ability. Puberty is the last step in brain development and marks an important phase with regard to sexually dimorphic cognitive performance and behavior. The present study assessed possible sex differences in cognitive style before and after puberty in a WM place-learning task. Since nitric oxide (NO) is implicated in spatial learning and hippocampal function, and since brain NO(-)(2) + NO(-)(3) levels (stable metabolites of NO) display region-specific sex differences in rat brain, NO(-)(2) + NO(-)(3) levels were determined after behavioral testing. The sex-related style difference emerged very clearly but only in the adult rats, which suggests that the female behavioral strategy in the WM place-learning task requires the presence of female sex hormones at puberty. Although NO(-)(2) + NO(-)(3) levels were higher in the adult rats and males compared to prepubertal and female rats, respectively, no significant correlations emerged between brain NO and behavior. The fact that the behavioral sexually dimorphic cognitive-style effect observed here and in previous studies appears to emerge only after puberty suggests that awareness of such postpubertal sex differences may also be important in human educational and therapeutic contexts.

Nicotine interacts with sex in affecting rat choice between "look-out" and "navigational" cognitive styles in the Morris water maze place learning task

The effect of sex and nicotine on cognitive style was examined in rats using a water maze task that allows differentiation between cognitive ability and style. During the 12-day acquisition period with the platform in the same location (either visible or hidden) there were no effects or interactions attributable to nicotine and sex, either in terms of learning rate or asymptotic latency. On the final test day the platform was visible and shifted in its location, and on the first trial the new location was proximal to the rats starting position, in contrast to the more distal location of the platform during the previous acquisition days. This platform relocation presented the rats with a choice between two competing cognitive styles: using local visual (look-out) cues vs. navigational cues. Performance on the test day yielded a nicotine x sex interaction, such that only saline-treated female rats showed a clear preference for the perceptual-proximal look-out cognitive style by swimming straight to the newly-relocated visible platform with mean escape latency that approximated the limits of swimming speed. The other three groups did not differ from each other, and preferred navigational cues. The results show that male and female rats use different strategies in problem solving, and that nicotine shifts the female pattern to that of the male.

Nicotine modulates nitric oxide in rat brain

Nicotine exerts its central actions by regulating cationic fluxes through nicotinic acetylcholine receptors (nAChRs). By this effect, the drug likely also modifies events occurring beyond the nAChR, including the regulation of nitric oxide (NO) synthesis. The present study was undertaken to assess the effects of acute and chronic nicotine administration (0.4 mg/kg, s.c.) on levels of NO(-)(2)+NO(-)(3), stable metabolites of NO, in brain regions of male and female rats. Nicotine increased levels of the metabolites, and therefore presumably of NO, with sex differences in the degree of stimulation, the brain regions affected, and the variance between the effects of acute and chronic administration. Prior inhibition of NO synthase eliminated the effect of nicotine in all regions studied. While nicotine appeared to increase NO indirectly via glutamate receptors in the cortex and hippocampus, this was not true of the corpus striatum, where blocking NMDA-type glutamate receptors with MK-801 had no effect. The findings support the view that NO is likely involved in some of the central effects of nicotine.

The effects of melatonin on the antioxidant systems in experimental spinal injury

Melatonin has been recently shown by various in-vivo and in-vitro studies to exert potent neutralising effects on hydroxyl radicals, stimulate glutathione peroxidase (GSH-Px) activity, and protect catalase (CAT) from the destructive activity of hydroxyl radicals in neural tissue. We aimed to investigate the possible effects of pharmacological dose of melatonin on some of the antioxidant defence systems in an in-vivo study of experimental spinal injury. Seven groups of adult male Sprague Dawley rats were used in the following scheme: Group I: Naive (n = 6), Group II: Lesion (n = 8), Group III: Melatonin (n = 5), Group IV: Melatonin + Lesion (n = 8), Group V: Placebo + Lesion (n = 5), Group VI: Sham operation (n = 5), and Group VII: Placebo (n = 5). Experimental spinal injury was induced at level T7-T8 by 5 sec compression of the total cord with an aneurysm clip on anaesthetised and laminectomized animals. The total 10 mg/kg dose of melatonin (Sigma) dissolved in alcohol-water was administered i.p. four times in 2.5 mg/kg doses, at 20 min pre-, at the time of and at 1 h and 2h post-compression. At 24 +/- 2h post-injury, the rats were euthanized and the lesioned segments of cord were dissected and homogenised with special care taken to distribute equal amount of injured tissue in each sample for analysis of reduced glutathione (GSH), oxidised glutathione (GSSG), superoxide dismutase (SOD), and CAT activity. Compression injury decreased GSH/GSSG ratio significantly (p < .0001). Melatonin, by itself, significantly decreased GSSG content (p < .05) and increased CAT activity (p < .05) in the naïve rats. Melatonin treatment decreased GSSG activity, thus elevating GSH/GSSG ratio, and also increased SOD and CAT activity without reaching statistical significance in the lesioned animals. In conclusion, pharmacological dose of systemically applied melatonin seemed to support some features of the antioxidant defence systems in our hands.

Nitric oxide synthetase inhibition hinders facilitation of active avoidance learning by nicotine in rats

Nicotine produces dose-dependent enhancement of performance in an active avoidance test, and also increases the levels of NO2- and NO3-, which are stable metabolites of nitric oxide (NO), in various brain regions of rats. On the basis of these two observations, we hypothesized that the beneficial effect of nicotine on learning could result from increased NO in relevant brain regions. We therefore tested active avoidance performance in rats given L-Nomega-nitroarginine (L-NA) to inhibit NO synthetase (NOS) prior to nicotine administration. Male Sprague-Dawley rats received L-NA (30 or 50 mg/kg), nicotine (0.4 mg/kg), saline or combinations of these treatments before learning trials. Rats were also tested on the inclined plane, to assess the possible effects due to impairment of motor function by drug treatments on active avoidance learning. L-NA treatment impaired the acquisition of active avoidance learning, and this defect was partially overcome by the co-administration of nicotine. Nicotine facilitated learning and significantly increased the number of correct responses. The threshold for the effect of NOS inhibition on performance exceeded 30 mg/kg L-NA, whereas 50 mg/kg impaired learning and also eliminated the nicotine-induced enhancement of learning. On the fifth day of learning trials, no facilitation of learning by nicotine was observed in rats receiving either dose of L-NA. Our results suggest that NO is involved in the facilitation of active avoidance learning by nicotine.

Effects of laterality and sex on cognitive strategy in a water maze place learning task and modification by nicotine and nitric oxide synthase inhibition in rats

The aim of the present study was to investigate sex differences in learning strategies and to elucidate the mechanisms, which may underlie these differences. In two separate experiments, rats were presented with different strategies that could be employed to learn the position of a platform in a water maze (WM); furthermore, rats received treatments that could influence these strategies. In the first experiment, we demonstrated that the response-learning paradigm can be applied to the WM and can be compared with visually cued learning and reversal learning. Naïve rats of either sex could acquire this protocol relatively easily. On the probe trial, where the rats are presented with a choice between using response versus visually cued learning, initially response learning was preferred, however, during these experiments, laterality emerged as a significant factor and rats trained to turn right had difficulty in reversing the learned pattern to find the platform. The second part of our study evaluated the effects of nicotine and nitric oxide synthase (NOS) inhibition on the aforementioned parameters. Drug treatments impaired acquisition compared to saline treatments and the effect was more pronounced with NOS inhibition. During the probe trial, while NOS inhibition enhanced the right-side bias in both sexes, nicotine treatment had the same effect only in males. In conclusion, naïve rats can acquire place learning using visible cues or response learning; however, there is a right side bias in both sexes and the laterality effect is more pronounced in male rats. In drug-treated animals, while NOS inhibition enhances laterality (right bias) in both sexes similarly, nicotine modifies the cognitive strategy in a sexually dimorphic manner by augmenting the right bias only in male rats.

The effect of nitric oxide synthase inhibition on cognitive ability and strategies employed for place learning in the water maze: sex differences

Male and female rats use different cognitive strategies in the solution of place-learning problems in the water maze despite similar abilities. The female-type strategy has been negatively correlated with cortical nitric oxide (NO) metabolites. The present study aimed to examine the effect of NO synthase (NOS) inhibition (N(omega)-nitro-L-arginine, L-NA) on cognitive ability and strategy in the water maze, and to evaluate possible sex differences. In a 2 (male versus female) x2 (L-NA versus saline) factorial design, rats were trained to find the platform (visible or hidden), always in the same position, for 12 days. L-NA impaired acquisition, during the earlier phases and more prominently in females. This impairment was quite dramatic and unique to females during the first day that the platform was hidden following 3 days of visible-platform conditions. After acquisition, the visible platform's position was shifted, thereby presenting the rats with a choice (searching for the hidden platform in the previous location, i.e. adopting a conceptual cognitive style, or escaping to the visible platform in a new position, i.e. adopting a perceptual style). On the first of the four shift trials (where the newly positioned platform was proximal to the rat's starting position), female rats showed the previously found tendency to adopt a perceptual style escape directly in clear contrast to saline-treated males. The L-NA-treated males tended to manifest female-like perceptual style, suggesting that inhibition of NO synthesis in males weakened the tendency to choose a conceptual style in this shifted-platform task. The role of NO in both cognitive and non-cognitive psychological functions is discussed.

Immunohistochemical evaluation of cell proliferation and apoptosis markers in ovaries and uterus of tamoxifen-treated rats

The aim of the study was to evaluate the immunohistochemical expression of cell proliferation and apoptosis markers in the ovaries and uterus of tamoxifen-treated rats. Twelve rats (150-200 g) were divided into two equal groups. The study group received daily intraperitoneal injections of tamoxifen dissolved in 5% dimethyl sulfoxide (n= 6). The control group received only the vehicle (n= 6). The rats were sacrificed at the 20th day of injection and were perfused. The ovaries and uterus of the rats were extracted. The sections were immunohistochemically stained with cell proliferation marker Ki-67 and the apoptosis markers PTEN and CD95. The expressions of the markers were quantified by a semiquantitative H-score method in myometrium, endometrial glands, ovarian surface epithelium, ovarian follicles, corpus luteum, and ovarian stroma separately. The mean H-scores of CD95 and PTEN obtained from myometrium, glandular endometrium, ovarian surface epithelium, ovarian follicles, corpus luteum, and ovarian stroma did not show significant difference between the study and the control groups. Proliferative index (Ki-67) of endometrial glands was significantly higher in the study group than in the control group (P < 0.05). In addition, proliferative index (Ki-67) of corpus luteum was significantly higher in the study group than in the control group (P < 0.05). Tamoxifen treatment has a potential to stimulate the cell proliferation of endometrial glands and corpus luteum in tamoxifen-treated rats. Apoptosis markers of PTEN and CD95 did not demonstrate significant difference after the tamoxifen treatment.

Learning-induced changes in D2 receptors of rat brain are sexually dimorphic

Pharmacological agents known to stimulate monoamine systems improve memory, and destruction of the dopaminergic systems or dopamine depletion lead to impairments in various learning-related tasks. These reported effects of the central dopaminergic system imply the involvement of D2 receptors. The aim of the present study was to investigate changes in [3H]spiroperidol binding in seven areas of rat brain following informal and active avoidance learning. Littermate male and female rats were reared until 3 months of age in standard colony conditions and treated as active controls or in enriched environmental conditions and exposed to pole-jump active avoidance trials. Female rats acquired avoidance behavior more rapidly than males. Among the brain regions, only the hippocampus showed significant variations in D2 receptor binding between the groups; sex differences and learning-sex interaction were observed in the corpus striatum. There was an inverse correlation between learning performance and hippocampal D2 receptor binding. Our results show that learning affects hippocampal D2 receptors in a sexually dimorphic pattern.

Intersession interval affects performance in the Morris Water Maze

We have recently reported an effect that shows a sexually dimorphic difference in cognitive style rather than ability. The preparation for potentially producing this proximal perceptual style effect is one where rats are first given 4-trial daily acquisition sessions for 12 days with the platform always in the same position, but sometimes visible (perceptual, "look-out" condition) and sometimes hidden (conceptual, "navigational" condition). On the first, probe trial of the 13th day, the platform's position is shifted to a point very close (proximal) to the rat's starting position, and made visible. The proximal perceptual style (PPS) effect has emerged sexually dimorphically in that only females swam straight to the newly positioned proximal platform. Other studies have shown that the PPS effect is eliminated (with females behaving like males) by nicotine and prepubertal ovariectomy, and does not occur in prepubertal females. Also, as no sex-related effects emerged during acquisition during these studies, the PPS effect appears to be a function of cognitive style rather than ability. The present study varied age, and, in an effort to economize on time, shortened acquisition to 6 days by having morning and afternoon sessions each day. To our surprise, this relatively subtle psychological manipulation eliminated the PPS effect, and also yielded some sex- and age-related effects during acquisition: A male advantage was observed and prepubertal rats had longer escape latencies; there was no significant interaction between sex and age.

Possible supportive effects of co-dergocrine mesylate on antioxidant enzyme systems in aged rat brain

Free radical damage is implicated in the course of many diseases, including age-related dementias. Oxidative deamination of primary monoamino oxidase (MAO) produces NH3 and H2O2 with established or potential toxicity. MAO activity is increased in aged rat brain and significantly lowered by chronic hydergine (codergocrine mesylate, Sandoz) treatment. The aim of this study was to investigate the effects of hydergine on enzymatic antioxidant defense systems. Hydergine or vehicle was administered systemically to young (3 months) and aged (18 months) Sprague-Dawley rats for 20 days and 24 h after the termination of the treatment, superoxide dismutase (SOD) and catalase (CAT) activities were determined in some brain regions. SOD and CAT activities were higher in the aged animals and were further increased with hydergine treatment. The increase in SOD levels caused by hydergine treatment in the aged animals were the most prominent in the hippocampus and in the corpus striatum. There was no region-specific effect of hydergine treatment on CAT levels in aged animals. The possible causal relationship between increased MAO activity, a generator of free radicals, and increased antioxidant defense in aging brain require further investigation. Decreasing MAO levels and supporting the antioxidant enzymes may underlie the efficacy of hydergine in the treatment of age related cognitive decline.

Cocaine- and amphetamine-regulated transcript promoter regulated by nicotine in nerve growth factor-treated PC12 cells

Nicotine and cocaine- and amphetamine-regulated transcripts (CART) have several overlapping functions, such as the regulation of reward, feeding behavior, stress response, and anxiety. Previous studies showed that nicotine regulates CART expression in various brain regions. However, the molecular mechanisms underlying this regulation are not known. This study investigated the regulatory effect of nicotine on promoter activity of the CART gene in PC12 cells, which were differentiated into a neuronal phenotype by nerve growth factor (NGF) treatment. Two vectors containing reporter genes (Gaussia luciferase or mCherry) and the 1,140-bp upstream of the transcriptional start site of the mouse CART gene are used to analyze the CART promoter activity. Transient transfection of PC12 cells with either vector displayed strong promoter activity in both undifferentiated and differentiated PC12 cells. CART promoter activity in the PC12 cell line is increased by forskolin or NGF treatment. In differentiated PC12 cells, exposure to 50 nM nicotine for 6 h increased CART promoter activity. However, treatment with higher nicotine doses for 6 h and treatment with all nicotine doses for 24 h showed no effect. A nicotine concentration of 50 nM is comparable to brain nicotine levels experienced by chronic smokers over long periods of time. Taken together, these data indicate that nicotine may exert some of its actions through the regulation of CART transcription in the brain.

In vitro effects of ritodrine, magnesium sulfate and their combination on spontaneous contractions of myometrial strips of pregnant rat uteri

OBJECTIVE

To investigate in vitro effects of ritodrine, magnesium sulfate and their combination on spontaneous contractions of myometrial strips obtained from pregnant rat uteri.

METHOD

A total of 13 pregnant Sprague Dawley rats with weights between 180-200 g were used in this study. Three strips from each rat were kept in an organ bath containing 20 ml Krebs-Henseleit solution (pH: 7.4 and 37 degrees C). 10(-8) 10(-6) and 10(-4) M concentrations of ritodrine, magnesium sulfate and the combination was applied over myometrial strips in Groups I (n: 10), II (n: 10) and III (n: 8), respectively. Amplitude and frequency of spontaneous myometrial contractions, which were recorded at the beginning of each experiment, were considered as reference values. Amplitude and frequency changes in spontaneous myometrial contractions were calculated at approximately ten-minute intervals right after the application of drugs as the percentage of difference at the first reference response.

RESULTS

Magnesium sulfate application did not lead to any significant difference on the amplitude and frequency of contractions at any of its concentrations. 10 and 10(-4) M concentrations of ritodrine caused a significant decrease in the amplitude of contractions. It was also found that ritodrine significantly decreased the frequency values at all concentrations. A significant decrease in amplitude was observed at 10(-8) and 10(-6) M concentrations in the combination group. No significant decrease in frequency values was found at any concentration in the combination group.

CONCLUSION

The tocolytic effect of ritodrine is superior to that of magnesium sulfate.

The effects of hydergine on the MAO activity of the aged and adult rat brain

Despite the fact that hydergine has been used in the treatment of dementia for many years, its mechanism of action is still not clear. Current studies imply that the major effect of hydergine may be the modulation of synaptic neurotransmission rather than solely increasing blood flow as was once thought. A prominent feature that accompanies aging is an increase in monoamine oxidase (MAO) levels which results in decreased availability of catecholamines in the synaptic cleft. The aim of this study was to determine the effects of hydergine on the MAO activity in different brain regions (cortex, olfactory bulb, hypothalamus, hippocampus, striatum, cerebellum) of old (30 months) and adult (12 months) male Sprague-Dawley rats. In cortex and olfactory bulb MAO levels were higher in the aged group. In hippocampus and hypothalamus hydergine treatment caused significant decreases in MAO levels. An interaction between age and hydergine treatment was observed in the hypothalamus, hippocampus and cerebellum. The hydergine effect was more pronounced in the aged group in the hypothalamus and cerebellum, and more pronounced in the adult in the hippocampus. Our findings imply that increased brain MAO activity in aging can be modified by hydergine treatment in some brain regions.

Proliferative effects of different hormone regimens on mammary glands in ovariectomized rats

OBJECTIVE

To compare the proliferative effect of different hormone regimens and estrogen receptor modulation on mammary glands in a rat model of surgical menopause.

DESIGN

Experimental animal study.

SETTING

University Hospital.

INTERVENTION

In a rat model of surgical menopause, 78 adult Sprague Dawley female rats were ovariectomized and treated with estrogen, estrogen combined with continuous or intermittent progesterone or the estrogen receptor modulator raloxifene and their respective vehicle controls. Following intraperitoneal drug administration for 20 days, rats were perfused, mammary glands were removed, tissues were processed for immunohistochemical (Ki-67) and hematoxylin-eosin staining, and investigated under light microscope.

MAIN OUTCOME MEASURE

Histopathological examination of mammary glands and Ki-67 positive cells (proliferation index).

RESULTS

Histological examination showed dilatation in the duct cysts and vacuolization in the epithelial cells in groups receiving progestin, either intermittent or continuous. Histological findings in the raloxifene group were no different from the control group, and the atrophic terminal ductal lobular unit in adipose tissue rich stroma was similar to postmenopausal breast. In animals with a proliferative response, increased proliferation started and dominated in the terminal ductal lobular unit epithelium. Comparison of Ki-67 proliferation indices between groups revealed that estrogen alone or combined with intermittent progesterone yielded significantly higher Ki-67 indices compared to controls; estrogen combined with continuous progesterone also resulted in increasing the probability of proliferation, but the effect was not as pronounced as the other two groups. Raloxifene treatment, on the other hand, did not cause proliferation.

CONCLUSION

Estrogen alone or combined with progesterone may increase the risk of breast cancer by enhancing proliferation in the TDLU; raloxifen does not induce proliferation and may be a safe estrogen receptor modulator regarding its effects on mammary glands during menopause.

Effects of nicotine on active avoidance learning in rats: sex differences

Nicotine, a cognition enhancer and a drug of abuse, exerts its central actions through neuronal nicotinic acetylcholine receptors which show sexual dimorphism. This study tested the effects of nicotine on active avoidance learning in male and female rats. Three month-old Sprague-Dawley rats received varying doses of nicotine (0.2, 0.4 and 0.6 mg/kg) or saline s.c. before active avoidance learning trials (15 trials/day) for a period of 5 days. Behavioural testing was continued after the termination of nicotine treatment once a week for four weeks. Nicotine improved acquisition of active avoidance learning in a dose-dependent manner. In male rats nicotine was active at all doses tested whereas, in females, learning performance deteriorated at a dose of 0.6 mg/kg. In conclusion, nicotine pre-treatment affects active avoidance in a sexually dimorphic and dose-dependent manner.