Activity In Adult Male Rats Research Articles

The impact of social defeat on basomedial amygdala neuronal activity in adult male rats

Social stressors negatively impact social function, and this is mediated by the amygdala across species. Social defeat stress is an ethologically relevant social stressor in adult male rats that increases social avoidance, anhedonia, and anxiety-like behaviors. While amygdala manipulations can mitigate the negative effects of social stressors, the impact of social defeat on the basomedial subregion of the amygdala is relatively unclear. Understanding the role of the basomedial amygdala may be especially important, as prior work has demonstrated that it drives physiological responses to stress, including heart-rate related responses to social novelty. In the present study, we quantified the impact of social defeat on social behavior and basomedial amygdala neuronal responses using anesthetized in vivo extracellular electrophysiology in adult male Sprague Dawley rats. Socially defeated rats displayed increased social avoidance behavior towards novel Sprague Dawley conspecifics and reduced time initiating social interactions relative to controls. This effect was most pronounced in rats that displayed defensive, boxing behavior during social defeat sessions. We next found that socially defeated rats showed lower overall basomedial amygdala firing and altered the distribution of neuronal responses relative to the control condition. We separated neurons into low and high Hz firing groups, and neuronal firing was reduced in both low and high Hz groups but in a slightly different manner. This work demonstrates that basomedial amygdala activity is sensitive to social stress, displaying a distinct pattern of social stress-driven activity relative to other amygdala subregions.

Стимулювання системи протеїназа-інгібітор протеїназ у результаті імерсійної гіпотермії

The effect of immersion hypothermia (IН) on proteolysis activity in adult male rats, which was performed at 0 °C for 5 min in the “forced swimming” test, studied; the body temperature decreased to 27.5 ± 0.5°C. In blood serum and non-nuclear fractions of homogenates of cerebral cortex, hypothalamus, cerebellum, brainstem, lungs, heart, liver and kidneys tissues were determined the total proteinase activity (TPA), non-trypsin-like proteinases (NTPs), such as chymase, prostate-specific antigen, partially tonin, kallikrein rK9, as well as trypsin-inhibitory activity of α-1-proteinase inhibitor (α-1-PI), α-2-macroglobulin (α-2-MG) by highly sensitive (10-9–10-10 g) enzymatic methods. It is noted that IH led to the TPA increase in all studied tissues (4-84 times), which corresponds to the psycho-emotional effects and the phenomenon of hormesis. After 24 h, TPA decreased, remaining above the control level, and in the kidneys increased further (90 times). NTLP activity as a result of IH increased in blood serum and cerebellum, decreased in the hypothalamus, and after 24 h increased further in serum (7 times), cerebellum, and heart. The activity of α-1-PI also increased in the brainstem, lungs, heart and kidneys, and decreased after 24 h in serum below the control level, and in the brainstem remained high, protecting against proteolytic attack. The activity of α-2-MG increased in the hypothalamus, heart, and cerebral cortex, maximum in the brainstem (2-5 times), and after 24 h - more significantly (24 times), but there were no changes in the cerebellum, where its initial level is the biggest. Thus, the development of IG as a result of swimming in cold water for 5 min at 0oC has a stimulating effect on the body and leads to a significant activation of the reactions of limited proteolysis.

Assessment of antiandrogenic and antispermatogenic activity of Hedera nepalensis in adult male rats.

The use of medicinal plants for fertility regulation has been prevalent worldwide for many centuries. They possess natural substances having antiandrogenic properties and can be used as source of contraception. In the current study, methanolic leaf extract of Hedera nepalensis was evaluated for antiandrogenic and antispermatogenic activity in adult male rats through various reproductive parameters. Experimental findings showed significantly increased oxidative stress with reduced antioxidant activity at highest dose regimens in both in vitro and in vivo studies. Increased ROS generation and lipid peroxidation lead to DNA damage in rat sperm. In vivo determination of sperm parameters exhibited notable reduction in sperm motility, viability and DSP in dose-treated animals. Histopathological observations revealed reduced epithelial height and wider lumen having less number of spermatozoa in high-dose-treated groups. Additionally, a marked decline noted in Testosterone concentration in all extract treated groups, while plasma LH and FSH levels only in high-dose-treated groups were noted. The findings of the current study conclude that methanolic leaf extract of H.nepalensis has the potential to disturb male fertility by generating oxidative stress and hormonal imbalance leading to histological alterations and sperm DNA damage.

Sucrose exposure during gestation lactation and postweaning periods increases the pubococcygeus muscle reflex activity in adult male rats.

Erectile dysfunction is related to metabolic alterations produced by a high carbohydrate diet, which may affect muscle activity during penile reflex in adulthood. We determined whether sucrose water consumption during gestation lactation and postweaning affects pubococcygeus muscle (Pcm) activity during urethrogenital reflex in adult male rat offspring. Twelve female rats were mated and grouped in control mothers consumed tap water and sucrose mothers consumed sucrose water during gestation lactation. Male pups were weaned and assigned into four groups (n = 6 each): those from control mothers who continued drinking tap water (CM-CO group) or sucrose water (CM-SO group) until adult life, and those from sucrose mothers who drank tap water (SM-CO group) or continued drinking sucrose water (SM-SO group) until adult life. Body weight, Pcm activity during penile stimulation by bipolar electrodes and urethrogenital reflex were analyzed. A catheter was placed into the urethra to record variations in urethral pressure after mechanical stimulation. Two-way ANOVA followed by post hoc tests were used considering P ≤ 0.05 as a significant difference. Males from the SM-SO group showed weight gain compared to the control group (P < 0.001). Also, sucrose intake promoted high Pcm activity (P < 0.0001) but reduced urethrogenital reflex duration CM-CO vs CM-SO (P = 0.02); CM-CO vs SM-CO (P = 0.01); CM-SO vs SM-SO (P < 0.003); and SM-CO vs SM-SO (P < 0.002). Our results suggest that a combination of a sucrose-rich diet during gestation lactation and postweaning modifies Pcm activation during penile reflex. The urethrogenital reflex is a spinal ejaculatory-like reflex, these rats could have penile dysfunction equivalent to premature ejaculation in men.

Voluntary wheel running promotes improvements in biomarkers associated with neurogenic activity in adult male rats

In rodents, hippocampal neurogenesis and synaptogenesis phenomena are affected by exercise. However, the role of exercise parameters such as intensity, duration, and mode on molecular mechanisms involved in these processes has not been elucidated. In this study, we evaluated the effects of different intensities and modes of running on the expression of genes contributing to neuronal differentiation and synapse formation in the hippocampus of adult male rats. Adult male Wistar rats (n = 24) were randomly divided into control, low-intensity running (LIR), high-intensity running (HIR), and the voluntary wheel running (WR) conditions. Changes in the expression of microRNA-124 (miR-124), microRNA-132 (miR-132), and their respective targets, were analyzed using quantitative RT-PCR and Western blotting techniques. Our results showed that WR compared to treadmill running increased miR-124 and miR-132 expression, while reducing the expression of their respective targets, glucocorticoid receptor (GR), SRY-Box 9 (SOX9), and GTP-activated protein P250 (P250GAP). Differences in expression levels were statistically significant (ps < 0.05), except for the expression of GR in HIR (P = 0.09). Moreover, the expression level of gene coding for the transcription factor cAMP-response element binding protein (CREB) was significantly higher in the WR group compared to the treadmill running groups (P = 0.001). Western blotting techniques indicated that the level of the CREB protein was higher in WR compared to the other groups qualitatively. These findings demonstrated a more dramatic effect for voluntary running on biomarkers that are associated with stimulating neurogenesis and synapse formation in the hippocampus of male rats compared with forced treadmill running. In addition, greater positive effects were observed for lower-intensity treadmill running as compared with high-intensity running.

Serotonin 5-HT1A and 5-HT1B receptors co-mediate the RU 24969-induced locomotor activity of male and female preweanling rats

The serotonin (5-HT) 1A/1B agonist RU 24969 robustly increases the locomotor activity of adult male rats and mice; however, studies using selective antagonists alternately report that 5-HT1A, 5-HT1B, or both receptor types mediate RU 24969's locomotor activating effects. The purpose of the present study was to extend these past findings by administering a selective 5-HT1 agonist and/or antagonists to male and female preweanling rats. This age group was tested because younger rats often exhibit psychopharmacological responses that are quantitatively or qualitatively different from adult rats. In a series of experiments, male and female preweanling rats were pretreated with vehicle, the 5-HT1A antagonist WAY 100635 (0.5, 1, 5, or 10 mg/kg), or the 5-HT1B antagonists NAS-181 (5 or 10 mg/kg) or SB 216641 (5 or 10 mg/kg) 30 min before assessment of locomotor activity. Rats were injected with saline or RU 24969 immediately prior to testing. Results showed that RU 24969 (0.625, 1.25, 2.5, or 5 mg/kg) significantly increased the locomotor activity of both male and female preweanling rats (no sex differences were apparent). Antagonism of either the 5-HT1A or the 5-HT1B receptor was sufficient to significantly reduce the locomotor activity of RU 24969-treated preweanling rats. Unexpectedly, NAS-181 did not act as a silent receptor antagonist, as both doses of NAS-181 significantly increased the locomotor activity of saline-treated preweanling rats. In sum, the present results show that both the 5-HT1A and 5-HT1B receptor systems mediate locomotion during the late preweanling period, and this mediation does not vary according to sex.

Neonatal shaking brain injury changes psychological stress-induced neuronal activity in adult male rats

Neonatal shaking brain injury (SBI) leads to increases in anxiety-like behavior and altered hormonal responses to psychological stressors as adults. These abnormalities are hypothesized to be due to a change in sensitization in neuronal circuits as a consequence of neonatal SBI. We examined the effects of neonatal SBI on neuronal activity in the anxiety- and/or stress-related areas of adult rats using Fos immunohistochemistry. Exposure to a novel elevated plus maze (EPM) resulted in a marked increase in Fos expression in the parvocellular (PVNp) and magnocellular parts of the paraventricular nucleus and the ventral part of the bed nucleus of the stria terminalis (vBNST) of shaken rats (S group) compared to non-shaken control rats (C group). On the contrary, Fos expression was significantly lower in the medial nucleus of the amygdala and the ventral subiculum (vS) of S group rats than C group rats exposed to EPM. Although we found no significant correlation in the number of Fos-expressing cells in the vBNST and PVNp in the C group rats, these numbers were significantly correlated in the S group rats. Furthermore, in the S group rats, but not in the C group rats, the number of Fos-expressing cells in the vBNST was inversely correlated with that in the vS. Interestingly, previous neuronal tracing studies have demonstrated direct projections from the vS to the vBNST and from the vBNST to the PVNp. The present data suggest that neonatal SBI can alter neuronal activity in anxiety- and/or stress-related neuronal circuits.

Effect of methamphetamine exposure on sexual behavior and locomotor activity of adult male rats.

Drug addiction and its consequences on social life and behavior is currently a worldwide problem. Methamphetamine (MA) is one of the most abused psychostimulants in the Czech Republic. MA elevates mood, increases concentration, reduces appetite, and promotes weight loss. However, high doses and long-term abuse can induce psychosis, hallucinations, paranoia, violent behavior, and can lead to cardiovascular problems. Regarding its high prevalence and negative impact on health and social life, MA needs to be fully investigated. Previous studies have demonstrated the impairing effect of MA drug abuse on female behavior. However, MA's influence on male sexual behavior is not entirely clear. The aim of this study was to examine the effect of MA exposure on sexual behavior and spontaneous locomotor activity of adult male rats. MA was administrated subcutaneously at a dose of 5 mg/kg daily for a period of 30 days. The control group was exposed to saline (SA) at the same time and same volume. At the end of the application period, exposed male rats were paired with non-treated female rats, and their behavior was recorded for 2 h. Sexual mating behavior was described in terms of mounting frequency, intromission frequency, ejaculation frequency, sniffing time, intromission latency and the post-ejaculatory interval. Spontaneous locomotor activity in postnatally exposed male rats was studied using the Laboras apparatus. Acute doses of MA (1 mg/kg) or SA were administrated to probe the sensitizing effect of previous chronic MA exposure. Afterward, the animal was placed in an unknown environment and monitored for 1 h. Behavior was automatically evaluated using Laboras software by analyzing the following parameters: duration of locomotion (s), duration of immobility (s), rearing (vertical exploratory behavior), time spent grooming (s), average speed (mm/s), and distance traveled (m). Our results indicate that MA administration has a negligible effect on the sexual behavior of adult male rats. However, more experiments have to be performed to examine the influence of MA exposure on spermatogenesis and the behavior of offspring. Data from the Laboras test showed that MA exposure has a significant effect on locomotor activity in both acute as well as subchronic MA application. In conclusion, our results show that administration of MA in adult male rats does not affect sexual performance and motivation but does increase locomotor and exploratory activity in an unknown environment.

Thalamic Control of Cognition and Social Behavior Via Regulation of Gamma-Aminobutyric Acidergic Signaling and Excitation/Inhibition Balance in the Medial Prefrontal Cortex

BackgroundThe mediodorsal thalamus plays a critical role in cognition through its extensive innervation of the medial prefrontal cortex (mPFC), but how the two structures cooperate at the single-cell level to generate associated cognitive functions and other mPFC-dependent behaviors remains elusive. Maintaining the proper balance between excitation and inhibition (E/I balance) is of principal importance for organizing cortical activity. Furthermore, the PFC E/I balance has been implicated in successful execution of multiple PFC-dependent behaviors in both animal research and the context of human psychiatric disorders. MethodsHere, we used a pharmacogenetic strategy to decrease mediodorsal thalamic activity in adult male rats and evaluated the consequences for E/I balance in PFC pyramidal neurons as well as cognition, social interaction, and anxiety. ResultsWe found that dampening mediodorsal thalamic activity caused significant reductions in gamma-aminobutyric acidergic signaling and increased E/I balance in the mPFC and was concomitant with abnormalities in these behaviors. Furthermore, by selectively activating parvalbumin interneurons in the mPFC with a novel pharmacogenetic approach, we restored gamma-aminobutyric acidergic signaling and E/I balance as well as ameliorated all behavioral impairments. ConclusionsThese findings underscore the importance of thalamocortical activation of mPFC gamma-aminobutyric acidergic interneurons in a broad range of mPFC-dependent behaviors. Furthermore, they highlight this circuitry as a platform for therapeutic investigation in psychiatric diseases that involve impairments in PFC-dependent behaviors.

Transient Prepubertal Mifepristone Treatment Normalizes Deficits in Contextual Memory and Neuronal Activity of Adult Male Rats Exposed to Maternal Deprivation

Early life adversity is a well-known risk factor for behavioral dysfunction later in life, including the formation of contextual memory; it is also (transiently) accompanied by hyperactivity of the stress system. We tested whether mifepristone (MIF) treatment, which among other things blocks glucocorticoid receptors (GRs), during the prepubertal period [postnatal days (PND)26-PND28] normalizes memory deficits in adult male rats exposed to 24-h maternal deprivation (MD) at PND3. MD reduced body weight gain and increased basal corticosterone (CORT) levels during the PND26, but not in adulthood. In adulthood, contextual memory formation of MD compared to noMD (i.e., control) male rats was significantly impaired. This impairment was fully prevented by MIF treatment at PND26-PND28, whereas MIF by itself did not affect behavior. A second behavioral test, a rodent version of the Iowa Gambling Task (rIGT), revealed that flexible spatial learning rather than reward-based aspects of performance was impaired by MD; the deficit was prevented by MIF. Neuronal activity as tested by c-Fos staining in the latter task revealed changes in the right hippocampal-dorsomedial striatal pathway, but not in prefrontal areas involved in reward learning. Follow-up electrophysiological recordings measuring spontaneous glutamate transmission showed reduced frequency of miniature postsynaptic excitatory currents in adult CA1 dorsal hippocampal and enhanced frequency in dorsomedial striatal neurons from MD versus noMD rats, which was not seen in MIF-treated rats. We conclude that transient prepubertal MIF treatment normalizes hippocampus-striatal-dependent contextual memory/spatial learning deficits in male rats exposed to early life adversity, possibly by normalizing glutamatergic transmission.

The Association Between Effective Dose of Magnesium and Mild Compulsive Exercise on Spatial Learning, Memory, and Motor Activity of Adult Male Rats

One of the most important survival mechanisms is learning and memory processes. To emphasize the role of physical exercises and magnesium (Mg) in improvement of cognitive performance, we planned to investigate the effect of Mg and mild compulsive exercise on spatial learning and memory of adult male rats. Accordingly, we divided male Wistar rats into four groups: (I) control, (II) Mg treatment, (III) exercise, and (IV) Mg-exercise in the different dosages of Mg (0.5, 1, 1.5, and 2mmol/kbw) were injected in the form of gavage during 1week. Also, 1-week mild running on treadmill was used for exercise treatment. The Morris water maze (MWM) test and open field tool were used to evaluate spatial learning, memory, and motor activity, respectively. Our results clearly showed that 1mmol/kbw Mg was applied as an effective dosage. Strikingly, 1-week mild exercise on treadmill had no significant effect on spatial motor activity, learning, and memory. Feeding 1mmol/kbw Mg for a week showed a significant difference in learning and exploration stages. Compared to control animals, these results reveal exercise and Mg simultaneously had effect on learning and reminding. As a consequence, although mild exercise had no effect on motor activity and memory, Mg intake improved spatial learning, memory, and locomotor activity. The Mg feeding could be a promising supplemental treatment in the neurodegenerative disease. It is worthwhile to mention consumption of Mg leads to enhancement of memory, so animals find the hidden platform with the highest velocity.

Locomotor activity and tissue levels following acute administration of lambda- and gamma-cyhalothrin in rats

Pyrethroids produce neurotoxicity that depends, in part, on the chemical structure. Common behavioral effects include locomotor activity changes and specific toxic syndromes (types I and II). In general these neurobehavioral effects correlate well with peak internal dose metrics. Products of cyhalothrin, a type II pyrethroid, include mixtures of isomers (e.g., λ-cyhalothrin) as well as enriched active isomers (e.g., γ-cyhalothrin). We measured acute changes in locomotor activity in adult male rats and directly correlated these changes to peak brain and plasma concentrations of λ- and γ-cyhalothrin using a within-subject design. One-hour locomotor activity studies were conducted 1.5h after oral gavage dosing, and immediately thereafter plasma and brains were collected for analyzing tissue levels using LC/MS/MS methods. Both isomers produced dose-related decreases in activity counts, and the effective dose range for γ-cyhalothrin was lower than for λ-cyhalothrin. Doses calculated to decrease activity by 50% were 2-fold lower for the γ-isomer (1.29mg/kg) compared to λ-cyhalothrin (2.65mg/kg). Salivation, typical of type II pyrethroids, was also observed at lower doses of γ-cyhalothrin. Administered dose correlated well with brain and plasma concentrations, which furthermore showed good correlations with activity changes. Brain and plasma levels were tightly correlated across doses. While γ-cyhalothrin was 2-fold more potent based on administered dose, the differences based on internal concentrations were less, with γ-cyhalothrin being 1.3- to 1.6-fold more potent than λ-cyhalothrin. These potency differences are consistent with the purity of the λ-isomer (approximately 43%) compared to the enriched isomer γ-cyhalothrin (approximately 98%). Thus, administered dose as well as differences in cyhalothrin isomers is a good predictor of behavioral effects.

Involvement of nigral oxytocin in locomotor activity: A behavioral, immunohistochemical and lesion study in male rats

Oxytocin is involved in the control of different behaviors, from sexual behavior and food consumption to empathy, social and affective behaviors. An imbalance of central oxytocinergic neurotransmission has been also associated with different mental pathologies, from depression, anxiety and anorexia/bulimia to schizophrenia, autism and drug dependence. This study shows that oxytocin may also play a role in the control of locomotor activity. Accordingly, intraperitoneal oxytocin (0.5–2000μg/kg) reduced locomotor activity of adult male rats. This effect was abolished by d(CH2)5Tyr(Me)2-Orn8-vasotocin, an oxytocin receptor antagonist, given into the lateral ventricles at the dose of 2μg/rat, which was ineffective on locomotor activity. Oxytocin (50–200ng/site) also reduced and d(CH2)5Tyr(Me)2-Orn8-vasotocin (2μg/site) increased locomotor activity when injected bilaterally into the substantia nigra, a key area in the control of locomotor activity. Conversely, the destruction of nigral neurons bearing oxytocin receptors by the recently characterized neurotoxin oxytocin-saporin injected into the substantia nigra, increased basal locomotor activity. Since oxytocin-saporin injected into the substantia nigra caused a marked reduction of neurons immunoreactive for tyrosine hydroxylase (e.g., nigrostriatal dopaminergic neurons) and for vesicular glutamate transporters VGluT1, VGluT2 and VGluT3 (e.g., glutamatergic neurons), but not for glutamic acid decarboxylase (e.g., GABAergic neurons), together these findings suggest that oxytocin influences locomotor activity by acting on receptors localized presynaptically in nigral glutamatergic nerve terminals (which control the activity of nigral GABAergic efferent neurons projecting to brain stem nuclei controlling locomotor activity), rather than on receptors localized in the cell bodies/dendrites of nigrostriatal dopaminergic neurons.

Possible role of serotonin and neuropeptide Y on the disruption of the reproductive axis activity by perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS) is an endocrine disruptor, whose exposure can induce several alterations on the reproductive axis activity in males during adulthood. This study was undertaken to evaluate the possible role of serotonin and neuropeptide Y (NPY) on the disruption of the hypothalamic–pituitary–testicular (HPT) axis induced by PFOS in adult male rats. For that, adult male rats were orally treated with 0.5; 1.0; 3.0 and 6.0mg of PFOS/kg/day for 28 days. After PFOS exposure, serotonin concentration increased in the anterior and mediobasal hypothalamus as well as in the median eminence. The metabolism of this amine (expressed as the ratio 5-hydroxyindolacetic acid (5-HIAA)/serotonin) was diminished except in the anterior hypothalamus, with the doses of 3.0 and 6.0mg/kg/day, being this dose 0.5mg/kg/day in the median eminence. In general terms, PFOS-treated rats presented a decrease of the hypothalamic concentration of the gonadotropin releasing hormone (GnRH) and NPY. A diminution of the serum levels of the luteinizing hormone (LH), testosterone and estradiol were also shown. These results suggest that both serotonin and NPY could be involved in the inhibition induced by PFOS on the reproductive axis activity in adult male rats.

Temperament moderates the influence of periadolescent social experience on behavior and adrenocortical activity in adult male rats

Adolescence is a period of significant behavioral and physiological maturation, particularly related to stress responses. Animal studies that have tested the influence of adolescent social experiences on stress-related behavioral and physiological development have led to complex results. We used a rodent model of neophobia to test the hypothesis that the influence of adolescent social experience on adult behavior and adrenocortical function is modulated by pre-adolescent temperament. Exploratory activity was assessed in 53 male Sprague–Dawley rats to classify temperament and then they were housed in one of the three conditions during postnatal days (PND) 28–46: (1) with familiar kin, (2) with novel social partners, or (3) individually with no social partners. Effects on adult adrenocortical function were evaluated from fecal samples collected while rats were individually-housed and exposed to a 1-hour novel social challenge during PND 110–114. Adolescent-housing with novel or no social partners led to reduced adult glucocorticoid production compared to adolescent-housing with familiar littermates. Additionally, highly-exploratory pre-weanling rats that were housed with novel social partners during adolescence exhibited increased exploratory behavior and a more rapid return to basal glucocorticoid production in adulthood compared to those housed with familiar or no social partners during adolescence and compared to low-exploratory rats exposed to novel social partners. In sum, relatively short-term adolescent social experiences can cause transient changes in temperament and potentially longer-term changes in recovery of glucocorticoid production in response to adult social challenges. Furthermore, early temperament may modulate the influence of adolescent experiences on adult behavioral and adrenocortical function.

Effect of prenatal methamphetamine exposure and challenge dose of the same drug in adulthood on epileptiform activity induced by electrical stimulation in female rats

Our previous study demonstrated that chronic prenatal methamphetamine (MA) exposure and a single dose of MA in adulthood decrease focally induced epileptiform activity in adult male rats. As seizures are known to be dependent on sex and female estrous cycle, the goal of the present study was to examine the combined effect of prenatal MA exposure (5mg/kg) and the MA challenge dose (1mg/kg) in adulthood on electroencephalography (EEG) recordings and consequences of brain stimulation in freely moving adult female rats with respect to the estrous cycle. Overall, 12 groups of adult female rats were tested: prenatally MA-exposed, prenatally saline-exposed and rats without prenatal injections, each of these groups was either postnatally challenged with MA or with saline injection (MA–MA, MA–S; S–MA, S–S; C–MA, C–S) and further divided according to the stage of the estrous cycle to metestrus/diestrus (M/D) or proestrus/estrus (P/E). Seizures were induced by repetitive electrical stimulation (15s/8Hz) of sensorimotor cortex. Stimulation threshold, duration of afterdischarges (ADs), and presence and duration of spontaneous ADs (SADs) were evaluated. Additionally, behavior associated with stimulation and ADs, and occurrence of wet-dog-shakes (WDS) were analyzed. The present study demonstrates that the prenatal MA exposure decreased the seizure threshold in females in M/D, but not in females in P/E. In addition, prenatally MA-exposed M/D females injected with saline in adulthood had increased the duration of ADs as well as SADs. The challenge dose of MA also decreased the seizure threshold. Moreover, prenatal as well as adult MA administration decreased the number and occurrence of WDS, respectively. Thus, the present study demonstrates that the effect of prenatal MA exposure and challenge dose of the same drug on focally induced epileptiform activity in adult female rats depends on the estrous cycle.

Prolonged exposure to a low-dose of bisphenol A increases spontaneous motor activity in adult male rats

We investigated the effects of bisphenol A (BPA), an environmental endocrine-disrupting chemical, on spontaneous motor activity in adult male rats. The rats were implanted intraperitoneally with mini-osmotic pumps containing either BPA (50μg/kg body weight per day) in sesame oil (BPA-treated group) or sesame oil only (vehicle-treated group). Spontaneous motor activity during a 24-h period was measured over 5days from day 9 to day 13 after implantation using an animal movement analysis system. Spontaneous motor activity during the last 2 h of the dark phase and during the first 1-h of the light phase was increased in the BPA-treated group. Total spontaneous motor activity during the 12-h light phase, but not the 12-h dark phase, was higher in the BPA-treated group than in the vehicle-treated group. These findings suggest that BPA may induce hyperactivity in adult male rats during the 12-h light phase, especially during the 2 h immediately preceding sleep-onset and 1 h immediately following sleep-onset.

Silver Nanoparticles Decrease Body Weight and Locomotor Activity in Adult Male Rats

Silver nanoparticles (Ag-NPs) are widely used in FDA regulated products. The physical-chemical properties of Ag-NPs are characterized using various instruments. The dose-dependent activity and body weight alterations are evaluated after rats were exposed to Ag nanoparticles, suggesting a major human health risk, given the wide application of silver nanomaterials.

Effect of Post-Weaning Individual Housing on Autonomic Responses in Male Rats to Sexually Receptive Female Rats

Post-weaning individual housing induces significant alterations in the reward system of adult male rats presented with sexually receptive female rats. In this study, we examined the effects of post-weaning individual housing on autonomic nervous activity in adult male rats during encounters with sexually receptive female rats to assess whether different affective states depending on post-weaning housing conditions are produced. Changes in heart rate and spectral parameters of heart rate variability indicated that in post-weaning individually housed male rats, both sympathetic and parasympathetic activity increased with no change in the sympathovagal balance, while in post-weaning socially housed male rats, both sympathetic and parasympathetic activity decreased with a predominance of parasympathetic activity. These two patterns of shifts in sympathovagal balances closely resembled changes in autonomic nervous activity with regard to classical appetitive conditioning in male rats. The autonomic changes in male rats housed individually after weaning corresponded to changes associated with the reward-expecting state evoked by the conditioned stimulus, and the autonomic changes observed in male rats housed socially after weaning corresponded to changes associated with the reward-receiving state evoked by the unconditioned stimulus. These results suggest that different affective states were induced in adult male rats during sexual encounters depending on male–male social interactions after weaning. The remarkable change caused by post-weaning individual housing may be ascribed to alteration of the reward system during sexual encounters induced by deficiency of intermale social communication after weaning.

Postnatal challenge dose of methamphetamine amplifies anticonvulsant effects of prenatal methamphetamine exposure on epileptiform activity induced by electrical stimulation in adult male rats

Administration of psychostimulants is often associated with increased seizure susceptibility. In our previous studies prenatal methamphetamine (MA) exposure increased seizure susceptibility of adult rats in models of primarily or secondarily generalized seizures induced by convulsant drugs. The effect of a single MA challenge dose in adulthood on chemically induced generalized seizures however, depends on the prenatal MA exposure history. Thus, the present study used a model of focal electrical stimulation to determine whether prenatal MA exposure with or without the adult challenge MA dose has the same outcome in a focal seizure model. Total of six groups of adult male rats were tested (prenatally MA-exposed, prenatally saline-exposed and rats without prenatal injections), each of these groups was either postnatally challenged with MA or with vehicle injection (MA-MA, MA-S; S-MA, S-S; C-MA, C-S). Seizures were induced by repetitive electrical stimulation (15 s/8 Hz) of sensorimotor cortex. Stimulation threshold, duration of afterdischarges (ADs), and presence and duration of spontaneous ADs (SAD) were evaluated. Additionally, behaviors associated with stimulation and ADs, and occurrence of wet-dog shakes (WDS) were analyzed. Our data demonstrate that daily injection of MA (5 mg/kg) within prenatal period decreased the occurrence of WDS and SADs, and shortened the duration of ADs and SADs suggesting anticonvulsant effects. Moreover, the challenge dose of MA (1 mg/kg) increased seizure threshold in all groups of rats, shortened duration of ADs in controls and prenatally saline-exposed animals, shortened duration of SADs in prenatally saline-exposed rats and totally eliminated WDS in all groups. Thus, the present study demonstrates that both chronic prenatal MA exposure and a single dose of MA in adulthood decrease focally induced epileptiform activity in adult male rats.