Lutfiye Kanit

We have generated high- and low-nicotine preferring (high-NP, low-NP) rat lines using voluntary oral nicotine intake as the selection criterion. After nine generations, the estimated realized heritability for high intake was 0.26. The aim of the current study is to compare how nicotine withdrawal varies between these two lines. This new analysis would help elucidate if nicotine withdrawal and intake share common genetic mechanisms. After exposing male and female Sprague Dawley rats (F8 generation) to six weeks of nicotine exposure, nicotine was withdrawn. Somatic signs of withdrawal, locomotor activity, and weight were measured at 16 and 40h. One week after withdrawal, resumption of nicotine intake was determined. The High-NP line had higher nicotine intake before and after withdrawal than the Low-NP line. High-NP rats were more active than Low-NP rats, and locomotor activity decreased during withdrawal; this decrease was more pronounced in the High-NP line. High-NP rats gained more weight during withdrawal than Low-NP rats. Escape attempts decreased during withdrawal in all groups, but overall females demonstrated more escape attempts than males. The other somatic signs of withdrawal were higher during withdrawal compared to baseline and more pronounced in females. Selection for nicotine preference affected nicotine intake, locomotion and weight, suggesting the heritability of these traits. However, despite differences in nicotine preference and intake, high-NP and low-NP rats showed similar withdrawal responses: escape attempts decreased and somatic signs increased. Withdrawal responses of females were more pronounced than males suggesting sex differences in the negative affect induced by nicotine withdrawal. The major finding of this novel analysis is showing that nicotine preference does not predict withdrawal symptoms. This finding, together with sex differences observed during withdrawal, may contribute to a better understanding of nicotine dependence and have translational value in developing more effective strategies for smoking cessation.

Background/Aims. The aim of the present study is to investigate the effects of an estrogen receptor modulating agent tamoxifen, and different protocols of hormone replacement therapy that mimic clinical applications, on spatial learning and active avoidance learning in rats. Methods. We used 2 groups of normal rats for tamoxifen experiments (control group and drug group) and 4 groups for hormone replacement experiments: (1) ovariectomized rats with sesame oil injection, (2) ovariectomized rats with continuous estrogen injection, (3) ovariectomized rats with continuous combined estrogen and progesterone injection and (4) ovariectomized with continuous estrogen and intermittent (sequential) progesterone injection. Properly assigned control groups were used and cognitive processes were studied on animal models of surgical menopause using the Morris water maze and active avoidance learning paradigms. Results. In the Morris water maze no significant differences in spatial learning were o...

Nicotine addiction is a complex process that begins with self-administration. Consequently, this process has been studied extensively using animal models. A person is usually not called "smoker" if s/he has smoked for a week or a month in a lifetime; in general, a smoker has been smoking for many years. Furthermore, a smoker has free access to cigarettes and can smoke whenever she/he wants, provided there are no social/legal restraints. Subsequently, in an animal model of tobacco addiction, it will be desirable to expose the animal to free access nicotine for 24 hours/day for many weeks, starting at different stages of development.

The selective estrogen receptor modulators (SERMs) are compounds that activate the estrogen receptors with different estrogenic and antiestrogenic tissue-specific effects. The similar effects of SERMs on estrogen encourage the efforts in the research of neuroprotective effects of SERMs. In our study, the potential neuroprotective effects of raloxifene were investigated on the brain cortex of ovariectomized rats after kainic acid-induced oxidative stress. To show the neuroprotective effect of raloxifene against a neurodegenerative agent, kainic acid, expression of Bcl-2, total glutathione (GSH), and nitrite-nitrate levels were investigated in the rat brain cortex. Our results demostrate that raloxifene treatment against oxidative stress significantly increases the expression of Bcl-2 and the level of GSH in the brain cortex.

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.

Alzheimer's disease (AD) is the most common form of dementia and is characterized by the presence of senile plaques and neurofibrillary tangles, along with synaptic loss. The underlying mechanisms of AD are not clarified yet, but oxidative stress and mitochondrial dysfunction are important factors. Overactivation of poly(adenosine diphosphate ribose) polymerase-1 (PARP-1) enzyme has been known to cause neuroinflammation and cell death in neurodegenerative processes. The aim of the present study was to investigate the protective effects of the PARP-1 inhibitors, 3-aminobenzamide (3-AB) and nicotinamide (NA), against amyloid β peptide (1-42) (Aβ(1-42))-induced oxidative damage and mitochondrial reduction capacity on isolated synaptosomes. Rats were injected intraperitoneally with 3-AB (30-100 mg kg(-1)), NA (100-500 mg kg(-1)) or with saline for 7 days. Synaptosomes were incubated with 10-30 μM Aβ(1-42) or saline for 6 h at 37 °C. Ex vivo Aβ(1-42) treatment significantly induced o...

To elucidate sex differences in nicotine addiction and the underlying mechanisms of the conditioning aspects of nicotine, nicotine-induced conditioned place preference (CPP) was evaluated in male and female Sprague Dawley rats using a three-chambered CPP apparatus and a biased design. In a series of experiments, the dose-response curve was obtained, pairings between the drug and initially non-preferred versus preferred compartments were compared, and the involvement of mGluR5 receptors in nicotine-induced CPP was evaluated. Modulation of nicotine-induced CPP with mGluR5 inhibition was obtained by MPEP (2-methyl-6-(phenylethynyl)-pyridine hydrochloride). Our results show that nicotine induces CPP dose-dependently in male rats but not in female rats. The comparison of the biased protocol, pairing nicotine with the initially preferred and non-preferred chambers, indicated that nicotine-induced CPP in male rats under both conditions, but the effect was stronger when nicotine was paired with the initially non-preferred side. The selective mGluR5 antagonist MPEP inhibited nicotine-induced CPP in male rats. In conclusion, the results of the current study in rats demonstrate that the conditioning effect of nicotine is more important in males than in females. Furthermore, in line with reported findings, our results suggest that mGluR5 antagonism may be therapeutically useful in smoking cessation during the maintenance of smoking behavior when conditioning plays an important role, notwithstanding the fact that this effect is observed only in male rats, not in females.

The opioid/nociceptin receptors are involved in many neurological disorders such as Alzheimer's disease, Parkinson's disease and epilepsy. Kainic acid (KA) is an analog of the excitatory amino acid transmitter glutamate and the systemic administration of KA induces status epilepticus (SE) in rodents. In this study, we examined the alterations in the G-protein activity and the gene expression levels of mu, kappa, delta opioid and nociceptin receptors (MOPr, KOPr, DOPr and NOPr) as well as PNOC, the precursor polypeptide of nociceptin-OFQ (N/OFQ) in KA-induced seizures in the rat brain cortex. KA was used to create seizures with the dose of 10 mg/kg body weight i.p. Following the KA administration, the rats were observed for 3 h to assess seizure activity. Seizures occurred approximately 45 min after the KA injection. Only rats exhibiting full limbic seizures, forelimb clonus with rearing, were used in this study. All animals were decapitated 4 h after the administration of KA. Our [(35)S]GTPγS binding results showed that there was a significant difference in both the affinity and efficacy particularly one of NOPr stimulation following KA treatment. Slight, but significant increase was observed for MOPr. Moreover PNOC, NOPr and MOPr mRNA levels were increased by KA treatment but there were no significant changes in the levels of DOPr and KOPr mRNAs. These results show that the activities of opioid/nociceptin receptors can be modified by KA-treatment, and MOPr, PNOC and NOPr are the most responsive to KA-induced seizures in the rat brain cortex.

D-serine plays a significant role in neuronal activity, including learning, memory, neuronal migration at developmental stages, and cell-death signaling. It has been also suggested that D-serine can potantiate the neurotoxicity induced by N-methyl-D-aspartate (NMDA) receptor activation due to its coagonist function. However, little is known about the role of D-serine in oxidative stress mechanisms. The aim of this study was to determine the possible neurotoxic or oxidative effects of the dose- (50-200 mg/kg) and time-dependent (2 or 6 hours) D-serine administration on lipid, protein, DNA, mitochondrial integrity (i.e., function), levels of antioxidant enzyme activities (e.g., catalase, glutathione peroxidase, and superoxide dismutase), and glutathione (GSH) in the rat brain. Our results showed that D-serine significantly increases the levels of lipid peroxidation, protein carbonyls, and DNA damage. In addition, D-serine treatment changes cellular antioxidant status due to the decreased levels of antioxidant enzymes, GSH, and mitochondrial function. Therefore, it is concluded that the regulation of D-serine levels in the brain may be an important target for the development of neuroprotective strategies against neurodegenerative processes where excitotoxicity is involved.

1. Accumulated clinical evidence suggests that selective oestrogen receptor modulators (SERM), such as raloxifene, may be neuroprotective. Oxidative stress is a likely molecular mechanism in the neurotoxicity of kainic acid (KA), an excitotoxic substance. The expression levels of the apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) gene seem to correlate with cellular sensitivity to reactive oxygen species (ROS) and a reduction in the expression of APE/Ref-1 may cause oxidative DNA damage. 2. The aim of the present study was to assess the effects of KA and raloxifene on the level of APE/Ref-1 mRNA in the hippocampus of ovariectomized rats. The expression of the APE/Ref-1 gene was quantified using reverse transcription followed by real-time polymerase chain reaction. 3. The results show that the level of APE/Ref-1 mRNA increased significantly in raloxifene-treated rats. However, raloxifene treatment did not affect the seizure severity induced by KA. We also observed that raloxifene treatment against simultaneous KA injection maintained the increased level of APE/Ref-1 mRNA in the hippocampus. 4. Therefore, the results of the present study seem to support previous data suggesting the potential significance of raloxifene in neuroprotection.

This study aimed to assess the contribution of endothelial nitric oxide synthesis to the net responses of human peripheral blood vessels in vivo to the selective alpha(2)-adrenoceptor agonist dexmedetomidine. Two groups of healthy young men were studied. In the first experiment, after brachial plexus block, the responses of digital arteries to systemically administered dexmedetomidine (target plasma concentration 1.2 ng ml(-1)) were studied using a photoplethysmograph (n=10) during i.a. infusions of saline and the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (8 micromol min(-1)). In a separate experiment, after pre-treatment with acetylsalicylic acid, responses to increasing doses of dexmedetomidine (0.01-164 ng min(-1)) in the presence and absence of L-NMMA were compared in dorsal hand veins (DHV) (n=10) using linear variable differential transformers. L-NMMA significantly augmented dexmedetomidine-induced vasoconstriction of digital arteries as assessed by an increase in light transmission through a finger and by a decrease in finger temperature. The mean (95% confidence interval) extent of the additional effect of L-NMMA over the constrictor effect of dexmedetomidine alone was 19% (14-24) (P<0.0001). In DHV, L-NMMA had variable effects on the dexmedetomidine-constriction dose-response curve. In three subjects, the curve was shifted significantly to the left (with a >10-fold difference in ED(50)), but ED(50) was only marginally affected by L-NMMA in the other subjects (difference in ED(50) <five-fold). The endothelial NOS enzyme has a significant role in opposing the vasoconstrictor action of dexmedetomidine at drug concentrations within the therapeutic range.

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 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.

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.

Smoking continues to be a major health problem and unfortunately smoking cessation interventions have limited success; the conditioning effects of nicotine and individual differences in tobacco addiction are important factors that underlie this setback. The aim of the current study was to investigate nicotine-induced conditioned place preference (CPP) in male and female rats which were previously exposed to a free choice of oral nicotine or water and showed different preferences for nicotine; subsequently nicotine intake also varied between subjects. Exposure patterns were varied in three experiments to allow for assessing the effect of adult v.s. adolescent exposure. The design of CPP testing enabled testing for the possible confounding effects of withdrawal or tolerance. A total of 150 male and female rats were used in three experiments. The oral nicotine choice was provided for at least six weeks in all experiments. Our results replicate our previous findings that nicotine induces CPP in male, but not female rats not pre-exposed to nicotine. Previous nicotine exposure, irrespective of the amount of nicotine consumed, eliminated the conditioning effects of nicotine in a new context. The diminished CPP response was more pronounced in rats exposed to nicotine as adolescents than those exposed as adults. This reduced responsiveness cannot be explained by tolerance. The neuroplastic changes caused by chronic nicotine administration or the strong conditioning to receiving nicotine in the home cage before CPP testing may underlie the weakened responsiveness. These findings support the well known clinical notion that smoking cessation attempts are more successful in a novel environment, not previously connected with smoking.