The effects of GABAergic drugs on grooming behaviour in the open field

Bimodal Release Two-In-One Clonazepam Matrix Lozenge Tablets for Managing Anxiety-Related Disorders: Formulation, Optimization and In Vivo Evaluation

Clonazepam (CLZ), an antipsychotic drug reported for its efficiency in managing anxiety-related disorders, is being marketed only as conventional tablets. Some patients have abstention to swallow the conventional tablets; therefore, the proposed study was aimed at developing a buccal lozenge tablet by direct compression of two types of optimized granules. Conazepam’s water solubility was first enhanced by a solid dispersion technique for a fast and better dissolution of type 1 granules, while the impact of gelling polymers was investigated on controlled-release type 2 granules. The optimized formulae met the acceptable pharmacopeial limits for tablets’ evaluation. A differential scanning calorimetry study revealed the compatibility between the drug and used excipients. All formulae gave a burst release of CLZ in the first hour of investigation, followed by a sustained release over 24 h. The formula that showed the highest prolonged in vitro release (99.0 + 0.1%), following the Higuchi diffusion model (R2 = 0.99), was then selected for further study. The formula succeeded in controlling the induced stress in a rat model with a significant impact on the behavioral tests throughout the experiment. The results were further confirmed by a pharmacokinetic study that showed a significant increase in Cmax, Tmax, and AUC (1.5, 2, and 3.9 folds), respectively, compared to oral suspension. The newly proposed delivery system has proven a better efficacy with a reduced dosing frequency.

Dissection of the relationship between anxiety and stereotyped self-grooming using the Shank3B mutant autistic model, acute stress model and chronic pain model

Self-grooming is an innate, cephalo-caudal progression of body cleaning behaviors that are found in normal rodents but exhibit repetitive and stereotyped patterns in several mouse models, such as autism spectrum disorders (ASDs). It is also recognized as a marker of stress and anxiety. Mice with Shank3B gene knockout (KO) exhibit typical ASD-like behavioral abnormalities, including stereotyped self-grooming and increased levels of anxiety. However, the exact relationship between anxiety and stereotyped self-grooming in certain types of animal models is not clear. We selected three animal models with high anxiety to compare their self-grooming parameters. First, we confirmed that Shank3B KO mice (ASD model), acute restraint stress mouse model (stress model), and chronic inflammatory pain mouse model (pain model) all showed increased anxiety levels in the open field test (OFT) and elevated plus maze (EPM). We found that only the ASD model and the stress model produced increased total grooming duration. The pain model only exhibited an increasing trend of mean self-grooming duration. We used the grooming analysis algorithm to examine the self-grooming microstructure and assess the cephalo-caudal progression of grooming behavior. The results showed distinct self-grooming microstructures in these three models. The anxiolytic drug diazepam relieved the anxiety level and the total time of grooming in the ASD and stress models. The grooming microstructure was not restored in Shank3B KO mice but was partially relieved in the stress model, which suggested that anxiety aggravated stereotyped self-grooming duration but not the grooming microstructure in the ASD mouse model. Our results indicated that stereotyped behavior and anxiety may be shared by separate, but interacting, neural circuits in distinct disease models, which may be useful to understand the mechanisms and develop potential treatments for stereotyped behaviors and anxiety.

Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats

Efficient repetitive clinical use of morphine is limited by its numerous side effects, whereas analgesic tolerance necessitates subsequent increases in morphine dose to achieve adequate levels of analgesia. While many studies focused on analgesic tolerance, the effect of morphine dosing on non-analgesic effects has been overlooked. This study aimed to characterize morphine-induced behavior and the development and progression of morphine-induced behavioral tolerance. Adult male Sprague-Dawley rats were repetitively treated with subcutaneous morphine for 14 days in two dose groups (A: 5 mg/kg/day (b.i.d.) → 10 mg/kg/day; B: 10 mg/kg/day (b.i.d.) → 20 mg/kg/day). Motor behavior was assessed daily (distance traveled, speed, moving time, rearing, rotation) in an open-field arena, before and 30 min post-injections. Antinociception was measured using tail-flick and hot-plate assays. All measured parameters were highly suppressed in both dosing groups on the first treatment day, followed by a gradual manifestation of behavioral tolerance as the treatment progressed. Animals in the high-dose group showed increased locomotor activity after 10 days of morphine treatment. This excitatory phase converted to an inhibition of behavior when a higher morphine dose was introduced. We suggest that the excitatory locomotor effects of repetitive high-dose morphine exposure represent a signature of its behavioral and antinociceptive tolerance.

Effects of Three Consecutive Days of Morphine or Methadone Administration on Analgesia and Open-Field Activity in Mice with Ehrlich Carcinoma

This study assessed the exploratory behavioral responses in BALB/c mice inoculated with Ehrlich ascitic carcinoma after 3 consecutive days of treatment with morphine or methadone. Fifty-three female mice, 60 ± 10 d old, were used. Seven days after intraperitoneal tumor inoculation (2 × 10⁶ cells), the animals were randomized into 7 groups: morphine 5 mg/kg (MO₅), morphine 7.5 mg/kg (MO_7.5), morphine 10 mg/kg (MO₁₀), methadone 2.85 mg/kg (ME_2.85), methadone 4.3 mg/kg (ME_4.3), methadone 5.7 mg/kg (ME_5.7), and 0.9% NaCl (Saline) (n = 7). Drug treatments were administered subcutaneously every 6 h for 3 d. The animals were evaluated for analgesia using the mouse grimace scale (MGS) and for general activity using the open field test. The MGS was performed before tumor inoculation (day 0), on day 7 at 40, 90, 150, 240, and 360 min after drug injection, and on days 8 and 9 at 40, 150, 240, and 360 min after drug injection. The open field test was performed before tumor inoculation (day 0), on day 7 after inoculation at 40, 90, 150, 240, and 360 min after drug injection, and on days 8 and 9 after inoculation at 40, 150, and 360 min after drug injection. MGS results indicated that administration of morphine promoted analgesia for up to 240 min. Conversely, methadone reduced MGS scores only at 40 min. All tested doses promoted a significant dose-dependent increase in the total distance traveled and the average speed, and increase that was markedly pronounced on days 8 and 9 as compared with day 7. The frequencies of rearing and self-grooming decreased significantly after morphine or methadone administration. Despite the difference in analgesia, both drugs increased locomotion and reduced the frequency of rearing and self-grooming as compared with the untreated control animals.

Effects of olanzapine on anxiety-related behaviour in male and female rats assessed after 21-24 and 42-45 days of chronic treatment

Olanzapine can decrease anxiety and impair memory, but there is limited information about length of treatment or sex differences in its effectiveness. Therefore, effects of 21-24 and 41-45 days of treatment and sex differences on anxiety-related behaviour and spatial memory were assessed in PVG/c (PVG/c is the internationally recognised way of referring to this rat strain) male and female rats. From 70 days after birth (PND70), all rats received no drug or 6, 11 or 15 mg/kg/day olanzapine via drinking water. From PND91, they were given four daily tests in an open field, light-dark box, zero maze and Y maze, and then again 21 days later from PND112. At PND91-94, all olanzapine doses decreased open-field ambulation and walking, and 6 and 15 mg/kg/day decreased rearing, increased immobility while 15 mg/kg/day decreased shuttles in the light/dark box (all suggesting higher anxiety). At PND112-115, 11 mg/kg/day increased open-field ambulation, walking, rearing, centre occupancy and light/dark-box shuttles and light-side entries while decreasing open-field immobility and corner occupancy (all suggesting lower anxiety). There were also several results in the open field and light/dark box suggesting olanzapine decreased anxiety for males but increased it for females. A significant olanzapine-related preference for the novel Y-maze arm either improved spatial memory, or decreased anxiety. Olanzapine thus appeared anxiogenic after 21 days' treatment, becoming anxiolytic after 42 days. This could depend on the sex of the rats (females more responsive to lower doses), and the dose (11 mg/kg/day being most effective). Therefore, while olanzapine was generally anxiolytic, it also had some treatment length- and sex-related anxiogenic effects.

Taurine enhances voluntary alcohol intake and promotes anxiolytic-like behaviors in rats

Taurine is an amino acid usually added to energy drinks. In rodents, acute taurine administration decreases voluntary alcohol intake, and subchronic administration restores different behavioral features impaired by alcohol withdrawal. In the present study, we evaluated the effects of chronic taurine treatment on voluntary alcohol consumption and changes in behavioral parameters in rats. Adult male Wistar rats were divided into two groups and were allowed to choose from two bottles containing 20% alcohol or 0.08% saccharin (vehicle solution), or two bottles containing vehicle, 24 h per day, for 5 weeks. After 3 weeks, rats received 100 mg/kg taurine (TAU) or saline (SAL) intraperitoneally once a day for 2 weeks, and daily alcohol consumption was monitored. On days 22 and 33, rats were tested in the open-field, and on day 34, they were exposed to the light/dark task (LDT). Our results show for the first time that chronic taurine treatment enhanced voluntary alcohol intake and preference in rats, and that these changes were accompanied by an anxiolytic-like phenotype in alcohol-treated rats, possibly due to its synergistic effect with alcohol on the dopaminergic and GABAergic systems.

Changes in behavioral and neuronal parameters by alcohol, cigarette, or their combined use in rats

Few studies have explored the effects of the combined use of alcohol and cigarette in humans, despite its prevalence. Here we evaluated the effect of isolated and combined use on behaviors and neuronal parameters in rats. Male adult rats were divided into alcohol (AL, 2 g/kg, by oral gavage), cigarette smoke (TB, six cigarettes, by inhalation), combined use (ALTB), or control (CT, water by oral gavage and environmental air) groups, treated twice a day (09.00 and 14.00 h). After 4 weeks, the rats were tested in the open field for behavioral analysis and euthanized for brain volume estimation and counting of neurons in the hippocampus. All treatments increased locomotion, and this behavior was higher in the ALTB than TB group. Latency to exit from the central area was lower in the ALTB than in the AL or CT groups. Rearing behavior increased in TB and decreased in AL and ALTB rats. Combined ALTB rats significantly increased their grooming behavior. Only the AL group showed decreased neuron counts and increased brain volume. Our results show that the isolated and combined uses of alcohol and cigarette smoke have diverse effects on behavioral and neuronal parameters in rats after long-term treatment.

Commercial Formulation of Chlorpyrifos Alters Neurological Behaviors and Fertility

Pesticides are known to result in toxic insult. We aimed to evaluate Judo 40, the commercial formulation of chlorpyrifos on the neurological activities, fertility, and hormone levels of male rats. Male Wistar rats were treated orally with 1 mL of 20 or 50 mg/kg Judo 40. The doses were administered four times, twice a day. Sexual and exploratory behavior indices, fertility indices, serum androgen levels, blood acetylcholinesterase (BChE) levels, and neurological and muscular effects were evaluated. Serum testosterone and luteinizing hormone were significantly reduced in the rats receiving 50 mg/kg Judo 40. A reduction in viable implantation sites and live pups born were evident in the female rats mated with the male rats treated with the highest dose. Similarly, in the rats treated with the highest dose of Judo 40, a significant reduction in plasma BChE enzyme was observed. According to the results, prolonged Judo 40 exposure can cause impairment of the neurological alterations and sex hormones leading to impaired fertility. Therefore, chemical handlers should be educated on protection and risk minimization.

Intervention mechanism of repeated oral GABA administration on anxiety-like behaviors induced by emotional stress in rats

The purpose of this study was to investigate the effects and mechanism of repeated oral administration of gamma-aminobutyric acid (GABA) on anxiety-like behaviors induced by emotional stress. Male Sprague-Dawley rats were randomly divided into five groups (8 rats each): control, emotional stress model, three emotional stress + GABA-treated groups (0.5, 1, 2 mg/kg). The rats were given empty water bottles after the training of drinking water to induce emotional stress. Each group was treated with saline or different doses of GABA respectively for 21 consecutive days. Then open field and elevated plus maze were used to assess anxiety-like behaviors. Both frontal cortex and plasma NO metabolites nitrate and nitrite (NO_x) levels were determined spectrophotometrically. Results showed that oral administration of GABA significantly reversed the stress-induced anxiety-like negative responses dose-dependently. The frontal cortex NO_x levels were lower in stressed rats than in control group (P < 0.05), but higher in 2 mg/kg GABA-treated group than stress model group (P < 0.05). On the other hand, NOx levels in plasma showed a gradual decline trend. Collectively, these results suggest that short repeated oral administration of GABA has an anxiolytic-like effect possibly via preventing NO reduction caused by stress and improving availability of NO in the frontal cortex.

Hemisphere-dependent Changes in mRNA Expression of GABAA Receptor Subunits and BDNF after Intra-prefrontal Cortex Allopregnanolone Infusion in Rats

Allopregnanolone is a neurosteroid implicated in mood disorders such as depression and anxiety. It acts as a GABA_A receptor (GABA_AR)-positive allosteric modulator and changes the expression of GABA_AR subunits and of brain-derived neurotrophic factor (BDNF) in different brain regions. It has been demonstrated that such neurochemical changes may have an asymmetrical pattern regarding brain hemispheres. The aim of this study was to verify the behavioral and hemisphere-specific neurochemical effects of the bilateral intra-prefrontal cortex (intra-PFC) infusion of allopregnanolone in rats. Rats were exposed to the forced swim test and to the grooming microstructure test, followed by the right and left hemisphere-specific quantification of mRNA expression by Real-Time PCR of δ and γ2 GABA_AR subunits and BDNF in the PFC and in the hippocampus. Though we did not observe any significant effects in the behavioral tests, intra-PFC allopregnanolone infusion bilaterally increased the mRNA expression of the δ subunit in the same area and of BDNF in the hippocampus. Both mRNA expressions of the γ2 subunit and BDNF were higher in the right than in the left PFC of control animals, and the hemisphere differences were not seen after allopregnanolone infusion. Overall hippocampal BDNF expression was also higher in the right hemisphere, but this asymmetry was not normalized by allopregnanolone. No asymmetries or changes were observed in the hippocampal mRNA expression of GABA_AR subunits. These results point to a hemisphere-dependent regulation of GABA_AR subunits and BDNF that can be modulated by intra-PFC allopregnanolone infusion, even in the absence of associated behavioral effects.

Imidacloprid insecticide exposure induces stress and disrupts glucose homeostasis in male rats

In the present study, we evaluated the stress response in adult rats who were administered imidacloprid (IMI) orally in two doses (0.5 and 1.0mg/kg bw for 60days). It led to an alteration in the levels of cortisone and catecholamines and induced behavioral deficits, particularly in the animals exposed to the dose of 1.0mg/kg. IMI was further analyzed for the effect on glucose homeostasis in developing and adult rats at a dose of 1.0mg/kg bw where it elicited a hyperglycemic effect. Moreover, we observed an alteration in the mRNA levels of glucose transporters. Histopathological and immunohistochemical data displayed structural perturbations in pancreatic tissue with a decline in the expression of insulin and GLUT4, particularly in the developing rats. Collectively, IMI treatment resulted in stress represented by behavioral and biochemical changes, particularly at a dose of 1.0mg/kg bw. Moreover, IMI perturbed the glucose regulation through hyperglycemic activity in both developing and adult rats, an observation clearly evident in the developing rats.

Ketamine-induced behavioural and brain oxidative changes in mice: an assessment of possible beneficial effects of zinc as mono- or adjunct therapy

RATIONALE

We studied the influence of zinc, haloperidol or olanzapine on neurobehaviour (open-field, radial arm maze and elevated plus maze) and brain antioxidant status in vehicle- or ketamine-treated mice, with the aim of ascertaining the potentials of zinc in counteracting ketamine's effects.

OBJECTIVES

Experiment 1 assessed the effects of zinc in healthy animals and the relative degrees of modulation of ketamine's effects by zinc, haloperidol or olanzapine, respectively. Experiment 2 assessed the modulation of ketamine's effects following co-administration of zinc with haloperidol or olanzapine.

METHODS

Male mice weighing 18-20 g each were used. Animals were pretreated with ketamine (except vehicle, zinc, haloperidol and olanzapine controls) for 10 days before commencement of 14-day treatment (day 11-24) with vehicle, zinc, haloperidol or olanzapine (alone or in combination). Ketamine injection also continued alongside zinc and/or standard drugs in the ketamine-treated groups. Zinc, haloperidol and olanzapine were administered by gavage. Treatments were given daily and behaviours assessed on days 11 and 24. On day 24, animals were sacrificed and whole brain homogenates used for estimation of glutathione, nitric oxide and malondialdehyde (MDA) levels.

RESULTS

Ketamine increased open-field behaviours, nitric oxide and MDA levels, while it decreased working memory, social interaction and glutathione. Administration of zinc alone or in combination with haloperidol or olanzapine was associated with variable degrees of reversal of these effects.

CONCLUSION

Zinc may have the potential of a possible therapeutic agent and/or adjunct in the reversal of schizophrenia-like changes in behaviour and brain oxidative status.

Effects of acute caffeine on anxiety-related behavior in rats chronically exposed to the drug, with some evidence of possible withdrawal-reversal

For 20days male and female PVG/c hooded rats were provided with caffeinated (approximately 50mg/kg/day) or unadulterated drinking water, and then their anxiety-related behavior was observed in an open field and elevated plus maze. Their choices of a brightness change were also observed in a Y maze to assess any caffeine effects on spatial memory. 24h later, all rats were tested again following an intraperitoneal injection of 50mg/kg acute caffeine, or vehicle. Earlier chronic caffeine decreased ambulation, walking, rearing, center occupancy and increased immobility in the open field thereby suggesting increased anxiety. However, occupancy of the plus-maze open arms and the Y-maze novel arm were increased by caffeine for male rats, but decreased for females probably because of sex differences in control levels of the response rather than to drug effects on anxiety and memory respectively. Following caffeine withdrawal, acute caffeine had the opposite effect to chronic treatment namely, increased open-field ambulation, walking, center occupancy and decreased immobility and defecation for caffeine-naïve rats that were suggestive of decreased anxiety. Similar but more consistent effects (plus decreased emergence latencies from a darkened start box into the open field) also typified the caffeine-experienced rats which in this case may have been accentuated by caffeine withdrawal-reversal. There was no evidence of either chronic or acute caffeine affecting spatial memory measured in the Y maze. There were also examples of lower overall activity and higher anxiety in male rats, than in females, and some sex-dependent caffeine effects.

The Effects of Inflammatory Tooth Pain on Anxiety in Adult Male Rats

Introduction:

This study aimed to examine the effects of induced inflammatory tooth pain on anxiety level in adult male rats.

Methods:

The mandibular incisors of 56 adult male rats were cut off and prefabricated crowns were fixed on the teeth. Formalin and capsaicin were injected intradentally to induce inflammatory tooth pain. Diazepam treated group received diazepam 30 minutes before intradental injection. The anxiety-related behavior was evaluated with elevated plus maze test.

Results:

Intradental application of chemical noxious stimuli, capsaicin and formalin, significantly affected nociceptive behaviors (P<0.001). Capsaicin (P<0.001) and formalin (P<0.01) significantly increased the anxiety levels in rats by decrease in the duration of time spent in open arm and increase in the duration of time spent in closed arm. Rats that received capsaicin made fewer open arm entries compared to the control animals (P<0.05). Capsaicin (P<0.001) and formalin (P<0.01) treated rats showed more stretch attend postures compared to the control and sham operated animals. In diazepampretreated rats, capsaicin induced algesic effect was prevented (P<0.001).

Conclusion:

Inflammatory pulpal pain has anxiogenic effect on rats, whereas diazepam premedication showed both anxiolytic and pain reducing effects.

Alterations in behaviour, cerebral cortical morphology and cerebral oxidative stress markers following aspartame ingestion

OBJECTIVE

The study evaluated changes in open field behaviours, cerebral cortical histomorphology and biochemical markers of oxidative stress following repeated administration of aspartame in mice.

METHODOLOGY

Adult mice were assigned into five groups of twelve each. Vehicle (distilled water), or aspartame (20, 40, 80 and 160mg/kg body weight) were administered orally for 28days. Horizontal locomotion, rearing and grooming were assessed after the first and last dose of aspartame. Sections of the cerebral cortex were processed and stained for general histology, and also examined for neuritic plaques using the Bielschwosky's protocol. Glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE) immunoreactivity were assessed using appropriate antibodies. Aspartate and antioxidant levels were also assayed from cerebral cortex homogenates. Data obtained were analysed using descriptive and inferential statistics.

RESULTS

Body weight and food consumption decreased significantly with aspartame consumption. Locomotion, rearing and grooming increased significantly after first dose, and with repeated administration of aspartame. Histological changes consistent with neuronal damage were seen at 40, 80 and 160mg/kg. Neuritic plaque formation was not evident; while GFAP-reactive astrocytes and NSE-reactive neurons increased at 40 and 80mg/kg but decreased at 160mg/kg. Superoxide dismutase and nitric oxide increased with increasing doses of aspartame, while aspartate levels showed no significant difference.

CONCLUSION

The study showed morphological alterations consistent with neuronal injury and biochemical changes of oxidative stress. These data therefore supports the need for caution in the indiscriminate use of aspartame as a non-nutritive sweetener.

Neurobiology of rodent self-grooming and its value for translational neuroscience

Self-grooming is a complex innate behaviour with an evolutionarily conserved sequencing pattern and is one of the most frequently performed behavioural activities in rodents. In this Review, we discuss the neurobiology of rodent self-grooming, and we highlight studies of rodent models of neuropsychiatric disorders--including models of autism spectrum disorder and obsessive compulsive disorder--that have assessed self-grooming phenotypes. We suggest that rodent self-grooming may be a useful measure of repetitive behaviour in such models, and therefore of value to translational psychiatry. Assessment of rodent self-grooming may also be useful for understanding the neural circuits that are involved in complex sequential patterns of action.

Induced adverse effects of prenatal exposure to silver nanoparticles on neurobehavioral development of offspring of mice

Steadily increased use of silver nanoparticles (Ag-NPs), has increased the amount of its exposure to humans and animals. Current scarce knowledge about the influences of prenatal exposure to Ag-NPs on postnatal outcomes, motivated us to investigate whether being exposed to it during pregnancy has any effects on neurobehavioral development of the adult offspring. Thirty virgin female NMRI mice were mated and treated subcutaneously once every three days from gestation day 3 until delivery, by 0, 0.2 and 2 mg/kg of bodyweight (BW) of Ag-NPs. Behavioral functions of adult offspring including spatial memory, passive avoidance learning, stress, anxiety-like behaviors and locomotor activities were assessed by commonly used neurobehavioral paradigms and the results were compared according to treatment and sex. Prenatal exposure to Ag-NPs significantly impaired their cognitive behavior in the Morris water maze. Although no evidence was observed indicating more anxiety-like behaviors in the treated offspring in the elevated plus maze, the number of defecations and leanings in the open field assay and number of passages in the light-dark box were greater in groups prenatally treated by Ag-NPs. Most of the impairments were more apparent in the offspring which had been prenatally exposed to high doses of Ag-NPs, particularly female ones. The present study indicated that the exposure of pregnant animals to Ag-NPs may lead to various neurobehavioral disorders in their offspring. Thus, more attention should be paid to avoid exposure to Ag-NPs, especially from pregnant females.

Brain DNA damage and behavioral changes after repeated intermittent acute ethanol withdrawal by young rats

RATIONALE

Alcohol addiction causes severe problems, and its deprivation may potentiate symptoms such as anxiety. Furthermore, ethanol is a neurotoxic agent that induces degeneration and the consequences underlying alcohol-mediated brain damage remain unclear.

OBJECTIVES

This study assessed the behavioral changes during acute ethanol withdrawal periods and determined the levels of DNA damage and reactive oxygen species (ROS) in multiple brain areas.

METHODS

Male Wistar rats were subjected to an oral ethanol self-administration procedure with a forced diet where they were offered 8% (v/v) ethanol solution for 21 days followed by five repeated 24-h cycles alternating between ethanol withdrawal and re-exposure. Control animals received an isocaloric control diet without ethanol. Behavioral changes were analyzed on ethanol withdrawal days in the open-field (OF) and elevated plus-maze (EPM) tests within the first 6 h of ethanol deprivation. The pre-frontal cortex, hypothalamus, striatum, hippocampus, and cerebellum were dissected for alkaline and neutral comet assays and for dichlorofluorescein ROS testing.

RESULTS

The repeated intermittent ethanol access enhanced solution intake and alcohol-seeking behavior. Decreased exploratory activity was observed in the OF test, and the animals stretched less in the EPM test. DNA single-strand breaks and ROS production were significantly higher in all structures evaluated in the ethanol-treated rats compared with controls.

CONCLUSIONS

The animal model of repeated intermittent ethanol access induced behavioral changes in rats, and this ethanol exposure model induced an increase in DNA single-strand breaks and ROS production in all brain areas. Our results suggest that these brain damages may influence future behaviors.

γ-Aminobutyric acid neural signaling in the lateroanterior hypothalamus modulates aggressive behavior in adolescent anabolic/androgenic steroid-treated hamsters

Male Syrian hamsters (Mesocricetus auratus) treated with anabolic/androgenic steroids (AAS) during adolescence (P27-P56) display highly escalated and mature forms of offensive aggression correlated with increased γ-aminobutyric acid (GABA) afferent development as well as decreased GABAA receptors in the lateroanterior hypothalamus (LAH) - an area of convergence for developmental and neuroplastic changes that underlie offensive aggressive behaviors in hamsters. This study investigated whether microinfusion of a GABAA receptor agonist (muscimol; 0.01-1.0 pmol/l) or antagonist (bicuculline; 0.04-4.0 pmol/l) directly into the LAH modulate adolescent AAS-induced offensive aggression. Activation of LAH GABAA receptors enhanced adolescent AAS-induced offensive aggression, beginning at the 0.1 pmol/l dose, when compared with AAS-treated animals injected with saline into the LAH. Importantly, GABAA receptor agonism within the LAH significantly increased the frequency of belly/rear attacks, while simultaneously decreasing the frequency of frontal attacks. These data identify a neuroanatomical locus where GABAA receptor activation functions to enhance aggression in adolescent AAS-treated animals, while also promoting the display of mature forms of aggression and suppressing juvenile play behaviors.

Central depressant and nootropic effects of daytime melatonin in mice

Background

Effects of orally administered daytime melatonin on novelty induced behaviors and spatial working memory in mice were evaluated using the open field, the Y maze and the radial arm maze.

Purpose

To ascertain the possible nootropic and/or central excitatory or inhibitory effects of daytime oral melatonin in mice.

Methods

Adult male mice from our colony, assigned to three and four groups for open field tests and memory tests respectively were given vehicle (normal saline), a standard drug Scopolamine at 0.5 mg/kg i.p, single dose, 30 minutes before behavioral study) or one of two doses of melatonin (5 and 10 mg/kg daily for a period of 30 days). All administrations were done between 8.00 a.m. and 9.00 a.m. daily. Behavioral tests were carried out on day 30 after administration. Results were analysed using a one-way ANOVA followed by a posthoc test (Student-Newman-Keul’s) and expressed as mean ± S.E.M.

Results

Open field tests revealed a significant reduction in rearing and grooming behaviors at both doses tested while no significant changes in horizontal locomotion were seen. Y maze studies showed an improvement in spatial memory in mice that received 5 mg/kg of melatonin when compared to scopolamine control. At 10 mg/kg, no significant improvement was seen. A significant increase in the radial arm maze spatial working memory following melatonin administration was seen at 5 mg/kg and 10 mg/kg compared to scopolamine control. Radial arm maze exploration was also significantly reduced.

Conclusion

The study demonstrates the ability of exogenously administered melatonin, to affect both central excitation and spatial working memory in mice even when given orally.

Tests of unconditioned anxiety - pitfalls and disappointments

The plus-maze, the light-dark box and the open-field are the main current tests of unconditioned anxiety for mice and rats. Despite their disappointing achievements, they remain as popular as ever and seem to play an important role in an ever-growing demand for behavioral phenotyping and drug screening. Numerous reviews have repeatedly reported their lack of consistency and reliability but they failed to address the core question of whether these tests do provide unequivocal measures of fear-induced anxiety, that these measurements are not confused with measures of fear-induced avoidance or natural preference responses - i.e. discriminant validity. In the present report, I examined numerous issues that undermine the validity of the current tests, and I highlighted various flaws in the aspects of these tests and the methodologies pursued. This report concludes that the evidence in support of the validity of the plus-maze, the light/dark box and the open-field as anxiety tests is poor and methodologically questionable.

Highly Palatable Food during Adolescence Improves Anxiety-Like Behaviors and Hypothalamic-Pituitary-Adrenal Axis Dysfunction in Rats that Experienced Neonatal Maternal Separation

BACKGROUND

This study was conducted to examine the effects of ad libitum consumption of highly palatable food (HPF) during adolescence on the adverse behavioral outcome of neonatal maternal separation.

METHODS

Male Sprague-Dawley pups were separated from dam for 3 hours daily during the first 2 weeks of birth (maternal separation, MS) or left undisturbed (nonhandled, NH). Half of MS pups received free access to chocolate cookies in addition to ad libitum chow from postnatal day 28 (MS+HPF). Pups were subjected to behavioral tests during young adulthood. The plasma corticosterone response to stress challenge was analyzed by radioimmunoassay.

RESULTS

Daily caloric intake and body weight gain did not differ among the experimental groups. Ambulatory activities were decreased defecation activity and rostral grooming were increased in MS controls (fed with chow only) compared with NH rats. MS controls spent less time in open arms, and more time in closed arms during the elevated plus maze test, than NH rats. Immobility duration during the forced swim test was increased in MS controls compared with NH rats. Cookie access normalized the behavioral scores of ambulatory and defecation activities and grooming, but not the scores during the elevated plus maze and swim tests in MS rats. Stress-induced corticosterone increase was blunted in MS rats fed with chow only, and cookie access normalized it.

CONCLUSION

Prolonged access to HPF during adolescence and youth partly improves anxiety-related, but not depressive, symptoms in rats that experienced neonatal maternal separation, possibly in relation with improved function of the hypothalamic-pituitary-adrenal (HPA) axis.

Hydroalcoholic extract of Urtica circularis: a neuropharmacological profile

CONTEXT

The genus Urtica has been known since ancient times. It has known to be useful for the treatment of different human ailments.

OBJECTIVE

The present work evaluated the neuropharmacological effects of a hydroalcoholic extract of Urtica circularis (Hicken) Sorarú (Urticaceae). materials and method: The effect on central nervous system of U. circularis hydroalcoholic extract (from leaves and stems) administered by the intraperitoneal route in mice was evaluated by several tests: Pentobarbital- and midazolam-induced hypnosis, open field, hole board, elevated plus-maze and forced swimming. Phytochemical analysis was performed by high-performance liquid chromatography.

RESULTS

A total of 300 mg/kg i.p. of the extract produced a significant prolongation of pentobarbital- (40 mg/kg i.p.; 60.1 min versus 25.4 min) and midazolam- (50 mg/kg i.v.; 53.4 min versus 25.1 min) induced sleeping time. The extract's administration caused a marked reduction of the head-dipping response (DE50: 373 mg/kg i.p.) in the hole-board test. Urtica circularis extract (DE50: 46 mg/kg i.p.) reduced the spontaneous locomotor activity in the open field test. Flumazenil and atropine significantly antagonized the extract's effect on the locomotor activity. No motor coordination disturbance was observed in the rota rod test at any doses. In the forced swimming test, the extract did not produce any change in the immobility time and it had no significant effects in elevated plus maze test. The phytochemical analysis revealed the presence of chlorogenic acid, vanillic acid, caffeic acid, vicenin-2, p-cumaric acid, ferulic acid, vitexin and isovitexin.

CONCLUSION

This study revealed that U. circularis hydroalcoholic extract possesses sedative activity, facilitating GABAergic and cholinergic transmission.

The effect of intra-nucleus accumbens administration of allopregnanolone on δ and γ2 GABA(A) receptor subunit mRNA expression in the hippocampus and on depressive-like and grooming behaviors in rats

Alterations in GABA(A) receptor expression have been associated with the allopregnanolone (3α-hydroxy-5α-pregnan-20-one; 3α,5α-THP) antidepressant-like effect in rats. The present study aimed to verify the effect of bilateral, intra-nucleus accumbens core (intra-AcbC) administration of the neurosteroid allopregnanolone on behaviors in the forced swim and grooming microstructure tests and in the δ and γ2 GABA(A) receptor subunit mRNA expression in right and left hippocampus of rats. The results of this study showed that bilateral, intra-AcbC allopregnanolone administration (5μg/rat) presented antidepressant-like activity in the forced swim test concomitant with an increase in climbing. Allopregnanolone at doses of 1.25 and 5μg/rat also decreased the percentage of correct transitions in the grooming microstructure test. Both δ and γ2 GABA(A) subunit expressions increased in the rat hippocampus after allopregnanolone intra-AcbC treatment. Our findings point to asymmetrical GABA(A) receptor expression changes in the hippocampus of animals treated with allopregnanolone. Further investigation should evaluate the antidepressant-like effect of allopregnanolone not only in other directly infused regions but also with respect to changes in other brain areas of the limbic system to understand allopregnanolone's mechanism of action.

Deficiency of antinociception and excessive grooming induced by acute immobilization stress in Per1 mutant mice

Acute stressors induce changes in numerous behavioral parameters through activation of the hypothalamic-pituitary-adrenal (HPA) axis. Several important hormones in paraventricular nucleus of the hypothalamus (PVN) play the roles in these stress-induced reactions. Corticotropin-releasing hormone (CRH), arginine-vasopressin (AVP) and corticosterone are considered as molecular markers for stress-induced grooming behavior. Oxytocin in PVN is an essential modulator for stress-induced antinociception. The clock gene, Per1, has been identified as an effecter response to the acute stresses, but its function in neuroendocrine stress systems remains unclear. In the present study we observed the alterations in grooming and nociceptive behaviors induced by acute immobilization stress in Per1 mutant mice and other genotypes (wild types and Per2 mutant). The results displayed that stress elicited a more robust effect on grooming behavior in Per1 mutant mice than in other genotypes. Subsequently, the obvious stress-induced antinociception was observed in the wild-type and Per2 mutant mice, however, in Per1 mutant, this antinociceptive effects were partially-reversed (mechanical sensitivity), or over-reversed to hyperalgesia (thermal sensitivity). The real-time qPCR results showed that in PVN, there were stress-induced up-regulations of Crh, Avp and c-fos in all of genotypes; moreover, the expression change of Crh in Per1 mutant mice was much larger than in others. Another hormonal gene, Oxt, was up-regulated induced by stress in wild-type and Per2 mutant but not in Per1 mutant. In addition, the stress significantly elevated the serum corticosterone levels without genotype-dependent differences, and accordingly the glucocorticoid receptor gene, Nr3c1, expressed with a similar pattern in PVN of all strains. Taken together, the present study indicated that in acute stress treated Per1 mutant mice, there are abnormal hormonal responses in PVN, correlating with the aberrant performance of stress-induced behaviors. Therefore, our findings suggest a novel functional role of Per1 in neuroendocrine stress system, which further participates in analgesic regulation.

Conditioned lick behavior and evoked responses using whisker twitches in head restrained rats

To examine whisker barrel evoked response potentials in chronically implanted rats during behavioral learning with very fast response times, rats must be calm while immobilized with their head restrained. We quantified their behaviors during training with an ethogram and measured each individual animals' progress over the training period. Once calm under restraint, rats were conditioned to differentiate between a reward and control whisker twitch, then provide a lick response when presented with the correct stimulus, rewarded by a drop of water. Rats produced the correct licking response (after reward whisker twitch), and learned not to lick after a control whisker was twitched. By implementing a high-density 64-channel electrocorticogram (ECoG) electrode array, we mapped the barrel field of the somatosensory cortex with high spatial and temporal resolution during conditioned lick behaviors. In agreement with previous reports, we observe a larger evoked response after training, probably related to mechanisms of cortical plasticity.

Inactivation of the prelimbic, but not infralimbic, prefrontal cortex impairs the contextual control of response conflict in rats

One fundamental function of the prefrontal cortex (PFC) is to guide context-appropriate behaviour in situations of response conflict. Haddon and Killcross recently developed a task in rats which mimics some aspects of response conflict seen in human cognitive paradigms such as the Stroop task. Using this paradigm they demonstrated that large PFC lesions including the prelimbic (PL), infralimbic (IL) and anterior cingulate cortices (ACC) selectively impaired performance on incongruent trials which required the use of task-setting contextual cues to control responding in the face of ambiguous response information. The current experiment was conducted to determine whether specific PFC regions were responsible for the deficit in incongruent performance. Rats were trained on two instrumental biconditional discriminations, one auditory and one visual, in two different contexts. Following acquisition, rats were implanted with guide cannulae aimed at the PL or the IL cortices of the rat prefrontal cortex. Following retraining, rats received microinfusions of the GABA(A) agonist muscimol or artificial cerebrospinal fluid (aCSF) into either the PL or the IL prior to presentations of novel congruent and incongruent audiovisual compounds of the training stimuli in extinction. Results showed that temporary inactivation of the PL cortex led to a selective deficit on incongruent compound trials, but left congruent, and hence biconditional task performance intact. By contrast, IL inactivation had no effect on the accuracy of responding during either congruent or incongruent trials. These results suggest that the PL cortex is necessary for the use of task-setting contextual cues to control responding to conflicting information.

Behavioral changes induced by cocaine in mice are modified by a hyperlipidic diet or recombinant leptin

The objective of the present study was to determine if the acute behavioral effects of cocaine acutely administered intraperitoneally (ip) at doses of 5, 10 and 20 mg/kg on white male CF1 mice, 90 days of age, would be influenced by leptin acutely administered ip (at doses of 5, 10 and 20 microg/kg) or by endogenous leptin production enhanced by a high-fat diet. The acute behavioral effects of cocaine were evaluated in open-field, elevated plus-maze and forced swimming tests. Results were compared between a group of 80 mice consuming a balanced diet and a high-fat diet, and a group of 80 mice fed a commercially available rodent chow formula (Ralston Purina) but receiving recombinant leptin (rLeptin) or saline ip. Both the high-fat-fed and rLeptin-treated mice showed decreased locomotion in the open-field test, spent more time in the open arms of the elevated plus-maze and showed less immobility time in the forced swimming test (F(1,68) = 7.834, P = 0.007). There was an interaction between diets and cocaine/saline treatments in locomotion (F(3,34) = 3.751, P = 0.020) and exploration (F(3,34) = 3.581, P = 0.024). These results suggest that anxiolytic effects and increased general activity were induced by leptin in cocaine-treated mice and that low leptin levels are associated with behavioral depression. Chronic changes in diet composition producing high leptin levels or rLeptin treatment may result in an altered response to cocaine in ethologic tests that measure degrees of anxiety and depression, which could be attributed to an antagonistic effect of leptin.

The grooming analysis algorithm discriminates between different levels of anxiety in rats: potential utility for neurobehavioural stress research

Stress has long been known to affect grooming in rodent species, altering both its activity measures and behavioural microstructure. Since stress disturbs a general pattern of self-grooming uninterrupted cephalocaudal progression, the grooming analysis algorithm (Kalueff and Tuohimaa, Brain Res. Protocols, 2004; 15: 151-8) was previously designed for mice to enable the detection of stress by measuring alterations in grooming microstructure in different test situations. Since mice and rats are known to differ in their behaviours, including grooming, the aim of the current study was to test our approach in rats and evaluate the utility of this method for differentiation between high- and low-stress situations. For this, we have developed the rat grooming analysis algorithm (based on ethological analysis of incorrect transitions contrary to the cephalocaudal rule, interrupted grooming activity and the assessment of the regional distribution of grooming) and applied this algorithm to the light-exposed (high stress) and dark-exposed (low stress) groups of rats. Here, we show that the percentage of 'incorrect' transitions between different grooming patterns, the percentage of interrupted grooming bouts and altered regional distribution of grooming (less caudal grooming, more rostral grooming) may be used as behavioural markers of stress in rats. Our results suggest that this method can be a useful tool in neurobehavioural stress research including modelling stress-evoked states, psychopharmacological or behavioural neurogenetics research in rats.

Neuronal nitric oxide synthase knock-out mice show impaired cognitive performance

Nitric oxide (NO) plays a role in a series of neurobiological functions, underlying behavior and memory. The functional role of nNOS derived NO in cognitive functions, however, is elusive. We decided to study cognitive functions in the Morris water maze (MWM) and the multiple T-maze (MTM) in 3-month-old male nNOS-knock-out mice (nNOS KO). To study the influence of neurology and behavior, we performed tests in an observational battery, the rota-rod, the elevated plus maze (EPM), the open field (OF), and a social interaction test. In the memory and relearning task of the MWM, most nNOS KO failed whereas performing better in the MTM. nNOS KO displayed significantly increased frequency of grooming, center crossings, and entries into the center in the OF. The observational battery revealed significantly increased scores for touch-escape reaction, body position, locomotion, and pelvic- and tail-elevation together with reduced vocalization. In the EPM, the time spent in the closed arm and the grooming frequency were significantly increased whereas urination was absent. We conclude that nNOS KO show impaired spatial performance in the MWM and herewith confirm the role of nNOS in cognitive functions such as processing, maintenance, and recall of memory. It must be taken into account that the major behavioral findings of increased grooming and anxiety-related behaviors may have led to impaired function in the MWM. The fact that nNOS KO performed well in the MTM, reflecting a low stress situation points to the interpretation that nNOS inhibition affects cognitive functions under stressful conditions (MWM) only.

Mouse grooming microstructure is a reliable anxiety marker bidirectionally sensitive to GABAergic drugs

Grooming is an important part of rodent behavioural repertoire, representing a complex hierarchically ordered cephalo-caudal sequence of patterns sensitive to stress and various drugs. Gamma-aminobutyric acid (GABA) is involved in the regulation of both anxiety and grooming behaviours. This study investigated the predictive validity of grooming behavioural microstructure as a marker of anxiety, by examining the effects of two GABAergic reference compounds, anxiolytic diazepam (0.1 and 0.5 mg/kg i.p.) and anxiogenic pentylenetetrazole (5 and 10 mg/kg i.p.) on mouse grooming. Our data suggest that the percentage of pattern transitions not fitting to the cephalo-caudal progression, and the percentage of interrupted grooming bouts are more reliable behavioural markers of stress bidirectionally sensitive to GABAergic anxiogenic and anxiolytic drugs, compared to the frequency and duration scores. Our study also confirms that detailed ethological analyses of grooming microstructure can be a useful tool in behavioural pharmacology of anxiety.

Anxiolytic-like profile in Wistar, but not Sprague-Dawley rats in the social interaction test

RATIONALE

The social interaction test is a valuable behavioural model for testing anxiolytic drugs in rodents, quantifying the level of social behaviour between pairs of rats.

OBJECTIVE

The aim of the present study was to assess the appropriateness of the social interaction test for use with a Sprague-Dawley rat line, because of increasing use of this strain in targeted mutagenesis research.

METHODS

Sprague-Dawley and Wistar rats received either diazepam or mCPP or were exposed to different environmental conditions (lighting, social isolation prior testing, habituation, testing-time). General anxiety-related parameters measured were: duration of active social contact, frequency of active social contact, latency to first contact. Different forms of active social contact were recorded: number of crawls, follows and sniffs. Secondly, aversion-induced hippocampal serotonin release and serotonin content in brain regions were measured.

RESULTS

In Wistar rats habituation to the test substantially increased the time of social contact, an effect comparable with treatment with diazepam (1 mg/kg), whereas changes in the lighting level had less impact. Latency to the first contact increased under "anxiety-reducing" conditions, the frequency of contacts did not change consistently. Sprague-Dawley rats behaviour did not change under varying environmental conditions, and treatment with diazepam had only sedating effects at higher doses (5 mg/kg). Anxiogenic doses of mCPP caused reduced social interaction in both strains. Serotonin release and serotonin content were higher in the anxious Wistar rats.

CONCLUSIONS

Different rat strains as well as differing test conditions have a major impact on the outcome of this animal test for anxiety.

Effects of adrenal medulla graft on recovery of GABAergic and dopaminergic neuron deficits in mice: behavioural, pharmacological and immunohistochemical study

We studied the capacity of adrenal medullary transplant to restore the deficits of GABAergic and dopaminergic neurons in mice injected with quinolinic acid (QA), using an open field test as well as pharmacological and immunohistochemical techniques. We analysed behavioural traits-total locomotor activity, peripheral and central activities, grooming, leaning and rearing in the QA-lesioned mice and mice that had undergone adrenal medulla (AM) transplantation. We found that the adrenal transplant recovered a loss of GABAergic neurons. It reduced QA-induced hyperactivity in locomotion and improved emotional indices. In addition, immunohistochemical studies of catecholaminergic markers-tyrosine hydroxylase (TH), dopamine (DA) and neuronal vesicular monoamine transporter type 2- and a single post-trial injection of tetrabenazine (TBZ; 5 mg/kg) indicated that catecholamines-synthesising chromaffin cells in the AM grafts were also involved in the beneficial effects. A likely interpretation of this behavioural pattern of results is that adrenal medullary transplants set into play an interaction between GABAergic and DAergic factors. Our results may contribute to the clarification of the beneficial effects of AM transplants in striatal function.

The open field as a paradigm to measure the effects of drugs on anxiety-like behaviors: a review

The open field is a very popular animal model of anxiety-like behavior. An overview of the literature on the action elicited by effective or putative anxiolytics in animal subjected to this procedure indicates that classical treatments such as benzodiazepine receptor full agonists or 5-HT(1A) receptor full or partial agonists elicit an anxiolytic-like effect in this procedure in most cases (approximately 2/3). However, compounds (triazolobenzodiazepines such as adinazolam and alprazolam, selective serotonin reuptake inhibitors) that have a different spectrum of therapeutic efficacy in anxiety disorders such as panic attacks, generalized anxiety disorder or obsessive-compulsive disorder were poorly effective as anxiolytics in the open field test, suggesting that this paradigm may not model features of anxiety disorders. The procedure is also relevant for the study of compounds endowed with anxiogenic effects, as such effects were detected after treatments with benzodiazepine receptor inverse agonists or with corticotropin releasing factor (CRF) receptor agonists.

Effects of dysthyroidism in plus maze and social interaction tests

The aim of the present study was to determine the influence of thyroid hormones on the anxiety of male Wistar rats. Dysthyroidism was induced by adding 20 mg of methimazole (100 ml) to their drinking water or by adding 0.3 mg of L-thyroxine (100 ml) to their drinking water from the ninth day of gestation. After weaning, the drugs were administered to young rats until the end of the experiment. Anxious behavior was measured using the elevated plus maze and social interaction tests when the animals were 85 days old. Chronic methimazole administration produced a significant anxiolytic pattern in both tests. In the plus maze test, the methimazole-treated animals entered and remained more time in the open arms than the control animals. In the social interaction test, they spent more time in bodily contact, and did this more frequently than those in the control group did. Results from this experiment suggest that chronic thyroid deficiency produces an anxiolytic-like effect in both tests.

Possible anxiolytic effects of ivermectin in rats

Ivermectin, a mixture of 22,23-dihydroavermectin B1a (> or = 80%) and B1b (< or =20%), is produced by Streptomyces avermectilis, an actinomycete. It is a macrocyclic lactone disaccharide, a member of the avermectin family, and is used as an antiparasitic drug. Previous studies performed in our laboratory showed that doramectin, another avermectin drug, interferes with GABAergic-related behaviours, leading to anxiety and seizures. The objective of the present study was to examine the effects of ivermectin (0.5 and 1.0 mg/kg) on the central nervous system of rats, using behavioural models related to GABAergic neurotransmission. A known anxiolytic drug, diazepam, was used as a positive control. Open field and elevated plus-maze behaviours, as well as conflict behaviour to a conditioned response, were assessed. The effects of ivermectin and diazepam in reversing the anxiety induced by picrotoxin was studied. The protective effects of ivermectin on pentylenetetrazole- and picrotoxin-induced seizures were also investigated. In the open field, 1.0 mg/kg ivermectin decreased locomotion frequency at 15 and 60 min of observation, rearing behaviour showed a biphasic effect at 15 and 30 min and duration of immobility was increased in all sessions after 1.0 mg/kg ivermectin. These data suggest anxiolytic or sedative effects. Ivermectin and diazepam both had a tendency to cause an increase both in the number of entries into the open arms and on the time spent in the open arms of an elevated plus-maze. Picrotoxin on its own reduced the number of entries as well as the time spent in the open arms. Both diazepam and ivermectin reversed these effects of picrotoxin. In conflict behaviour analysis, ivermectin and diazepam gave the classic effect of an anxiolytic drug, reversing the conditioned response to shock. Ivermectin protected rats from the convulsant effects of pentylenetetrazole but not from those of picrotoxin. Thus, ivermectin had the pharmacological profile of an anxiolytic drug with GABAergic properties. The lack of effect on seizures induced by picrotoxin suggests that the action of ivermectin is different from that of the benzodiazepine drugs.

Involvement of adrenal medulla grafts in the open field behavior

Immunohistochemical and behavioral techniques were used to study the effects of adrenal medulla grafts, implanted in striatum after bilateral kainic acid (KA) lesions of this structure, on the open field behavior of mice. KA-induced behavioral changes in leaning, grooming and locomotor activity of the open field test were significantly improved after grafting of the adrenal medulla, and in some respects, fully restored. Immunohistochemical identification showed that grafts contained neuron-like cells with a tyrosine hydroxylase (TH), phenylethanolamine N-methyltransferase, gamma-aminobutyric acid (GABA), choline acetyltransferase (ChAT), and enkephalin-like immunostainings. A likely interpretation of this complex pattern of results is that adrenal medullary grafts may restore the deficits of GABAergic neurons which in turn reverse the abnormalities in emotionality and locomotion. Neurobiologically, these behavioral improvements probably involve GABAergic and catecholaminergic factors of adrenal medulla grafts, although other neuroactive substances, such as acetylcholine and enkephalins, cannot be excluded.

Developmental lead exposure in rats: is a behavioral sequel extended at F2 generation?

Lead toxicity was studied in rats exposed from conception until weaning and assessed by monitoring offspring behavior in both the open field and elevated plus maze and by determining tissue lead in an assessment schedule extended to first (F1) and second (F2) generations. Dams utilized for the F1 generation were submitted to 750 ppm of lead (acetate) in drinking water during pregnancy and lactation. For F1 pups, behavioral alterations were not detected in the elevated plus maze, while in the open field, spontaneous locomotor activity as well as time of both grooming and rearing increased, while freezing time decreased in 30- and 90-day-old rats. Lead content was higher in tissues of 1- and 30-day-old pups. However, in 90-day-old rats, lead was detected only in the femur. F2 generation was lead-free but still presented alterations in both locomotor activity and grooming in 30- and 90-day-old pups. It appears that developmental lead exposure may cause behavioral effects during the developmental stage of the F1 generation, which remains throughout the animal's adult life as a sequel, regardless of lead accumulation, and is extended to the F2 generation of rats.

Anxiolytic and anticonvulsant properties of doramectin in rats: behavioral and neurochemistric evaluations

Doramecin is an antiparasitic drug that may interfere with gamma-aminobutyric acid (GABA) neurotransmission. Some behavioral manifestations are related with GABAergic neurotransmissions as anxiety and seizures. The objective of the present study was to examine the possible central nervous system (CNS) effects of doramectin (100, 300 and 1000 microg/kg, SC) in rats, using anxiety behavioral models, susceptibility to seizures and central neurotransmitter evaluations. The open-field results showed (i) few alterations in locomotion frequency; (ii) a biphasic effect on rearing frequency that may be the consequence of least habituation in open-field; (iii) the reduction of grooming durations might be attributed to a possible anxiolytic effect of doramectin since GABAergic agonists reduced this parameter in apparatus. Our data in the hole board showed no effects in locomotion and rearing frequencies but increased head dipping frequency of rats administered doramectin similarly to anxiolytic drugs. In plus-maze test, doramectin administration increased the number of entries and time into open arms, indicating also an anxiolytic effect. Doramectin protected animals from convulsant effects of picrotoxin, indicative of an anxiolytic pharmacological profile of a drug with GABAergic properties. The alterations observed in central dopaminergic, noradrenergic and serotoninergic neurotransmissions might be the consequence of reinforcement in central GABAergic neurotransmission induced by doramectin. The present results suggest that doramectin has the pharmacological profile of an anxiolytic/anticonvulsant drug with GABAergic properties.

Gabaergic-benzodiazepine system is involved in the crotoxin-induced anxiogenic effect

The behavioral effects of crotoxin (CTX), the major component of Crotalus durissus terrificus venom, were studied in rats submitted to the open field, holeboard, and social interaction tests. CTX (100, 250, and 500 microg/kg, i.p.) was administered 2 h before the tests. In the open field, CTX reduced ambulation (250 microg/kg) and rearing (250 and 500 microg/kg) and increased grooming (100 and 250 microg/kg) and freezing (250 microg/kg). In the holeboard and social interaction, all the CTX doses evaluated decreased, respectively, head dip and head dipping, and social interaction time. The CTX-induced behavioral alterations could be attributed to its neuromuscular transmission blockade, but this possibility was ruled out because CTX (250 and 500 microg/kg, i.p., 2 h before the rotarod test) was unable to modify the rotarod performance of rats. The involvement of the benzodiazepine receptor in the CTX-induced behavioral alterations was investigated through the pretreatment (30 min before the tests, i.p.) of the animals with diazepam (1.2 mg/kg), or flumazenil (4 and 10 mg/kg). Both diazepam and flumazenil antagonized the CTX-induced behavioral alterations in the open field, holeboard, and social interaction tests. This study demonstrated that: (1) CTX is an anxiogenic compound; and (2) the gabaergic-benzodiazepine system may play a role in the CTX-induced anxiogenic effect.