An isolated epileptic seizure elicits learning impairment which could be prevented by melatonin.

We tested the relation between a single short tonic-clonic seizure elicited by flurothyl vapors and changes of learning in Morris water maze (MWM) in Wistar rats. Oxidative stress usually accompanies seizures. Large melatonin doses were applied immediately before and after seizures to test consequences on learning impairment. One hour of hypobaric hypoxia (8000 m) three days prior to the seizure served as an activator of intrinsic antioxidant systems. Learning in MWM (7 days) started 24 h after seizures. Following seizures, latencies in MWM were longer than in controls and were shortened by hypoxia and preventive melatonin application. Melatonin was also applied before hypoxia to influence free radical (FR) production and intrinsic antioxidant activation. Some behavioral characteristics were changed and preconditioning effect of hypoxia was reduced. Melatonin after seizure (150 s and 6 h) had negligible effect. Results allow us to hypothesize about the role of FR and the beneficial effect of melatonin on the behavioral consequences of seizures.

Sex differences in social interaction of methamphetamine-treated rats.

Our previous study showed that single injection of methamphetamine decreases social interaction (SI) in a dose-dependent manner that was further affected by stressful environment conditions. The aim of this study was to examine the effect of methamphetamine and its interaction with gonadal hormones on SI. Adult male and female rats were gonadectomized and assigned to testosterone-treated and oil-treated groups in male rats and estradiol-treated and oil-treated groups in female rats, respectively. Hormones were administered 30 min before each habituation in the open field. All four hormonal groups were further divided to control (without injection), saline (1 ml/kg saline injection), and methamphetamine (1 mg/kg) groups. Injections were applied 30 min before the SI test. The total duration and the total number of SI and nonsocial behavioral patterns were assessed. This study showed that an acute methamphetamine administration in a dose of 1 mg/kg decreased different types of SI in both sexes. In contrast, the same dose of methamphetamine increased locomotion and rearing behavior in male and female rats. The frequency and/or duration of SI (especially mutual sniffing and allogrooming) was lower in adult female rats relative to gonadectomized male rats, but locomotion was increased in female relative to male rats regardless of the presence or absence of gonadal hormones. In conclusion, this study is novel especially because it examines SI in both sexes in relation to the presence or absence of gonadal hormones.

Modulations of behavioral consequences of minor cortical ischemic lesion by application of free radicals scavengers.

Functional and morphological consequences of ischemic lesions are partially related to the production of reactive oxygen species (ROS). The aim of the study was to create a unilateral photothrombic lesion with minimal morphological changes and minor sensorimotor and cognitive deficits and also to test whether the application of ROS scavengers after the end of induction of ischemia had improved the functional outcome. Adult Wistar male rats were randomly divided into five groups: naive control, sham operated animals, animals with induced ischemia, and two groups of animals with induced ischemia and subsequent ROS scavenger application -melatonin or tempol. The group subjected to ischemia showed a significant decline in performance in sensorimotor tests and the Morris water maze (MWM) test, compared to control animals. Tempol (50 mg/kg, i.p.) did not improve sensorimotor function and did not change spatial learning. Melatonin (100 mg/kg, i.p.), on the contrary, resulted in a significant improvement in animals' performances. All the ischemia subjected animals had increased speed of swimming in the MWM test, compared to the control group. Our findings showed that subsequent application of ROS scavengers improve ischemia outcomes, with melatonin being more potent. Conversely, neither melatonin, nor tempol decreased swimming speed cased by ischemia.

The effect of methamphetamine on social interaction of adult male rats.

The effect of psychostimulants on social behavior still remains unclear. Therefore the aim of the present study was to assess the effect of low doses of methamphetamine (MA) on social interaction (SI) in adult male rats. Rats were tested in three environmental conditions: (1) dimly lit, familiar environment, (2) dimly lit, unfamiliar environment and (3) intensely lit, unfamiliar environment considered to be low, middle and high stress, respectively. In each condition different set of animals was used. Rats were always divided into five groups. Control (without injection), saline (with 1 ml/kg saline injection) and three MA groups (doses: 0.5, 1 and 1.5mg/kg). Injections were applied 30 min prior to testing. Always a pair of unfamiliar rats of the same treatment group was tested. Their behavior was video recorded for 5 min in an open field. Times spent by SI (following, climbing, genital investigation, etc.) and non-social behavior (locomotion, rearing) were analyzed using a two-way ANOVA (drug treatment x stress condition). Our data demonstrate that all doses of MA, reduced SI. In addition, the unfamiliarity of the arena increased exploratory behavior (locomotion and rearing) in all treatment groups, while the SI was affected by the environmental condition only in controls or saline-treated rats, but not in MA-treated groups. In conclusion, our data demonstrate that MA administration impairs SI in dose- and stress condition-specific manner, however, some of our results may be due to increase locomotion and rearing induced by MA.