The effect of SSRIs on unconditioned anxiety: a systematic review and meta-analysis of animal studies.

RATIONALE: Selective serotonin reuptake inhibitors (SSRIs) are the first choice of treatment for anxiety-like disorders. However, which aspects of anxiety are affected by SSRIs is not yet fully understood. OBJECTIVE: We aimed to systematically review the effect of six clinically effective SSRIs on four aspects of unconditioned anxiety: approach-avoidance behaviour (elevated plus maze), repetitive behaviour (marble burying), distress behaviour (ultrasonic vocalization), and activation of the autonomous nervous system (stress-induced hyperthermia). METHODS: We identified publications by searching Medline and Embase databases and assessed the risk of bias. A random effects meta-analysis was performed and moderator effects were analysed with Bayesian penalized meta-regression. RESULTS: Our search yielded 105 elevated plus maze, 63 marble burying, 11 ultrasonic vocalization, and 7 stress-induced hyperthermia articles. Meta-analysis suggested that SSRIs reduce anxiety-like behaviour in the elevated plus maze, marble burying and ultrasonic vocalization test and that effects are moderated by pre-existing stress conditions (elevated plus maze) and dose dependency (marble burying) but not by duration of treatment or type of SSRI. The reporting quality was low, publication bias was likely, and heterogeneity was high. CONCLUSION: SSRIs seem to reduce a broad range of unconditioned anxiety-associated behaviours. These results should be interpreted with caution due to a high risk of bias, likely occurrence of publication bias, substantial heterogeneity and limited moderator data availability. Our review demonstrates the importance of including bias assessments when interpreting meta-analysis results. We further recommend improving the reporting quality, the conduct of animal research, and the publication of all results regardless of significance.

The impact of estrous cycle on anxiety-like behaviour during unlearned fear tests in female rats and mice: A systematic review and meta-analysis.

Anxiety fluctuates across the human menstrual cycle, with symptoms worsening during phases of declining or low ovarian hormones. Similar findings have been observed across the rodent estrous cycle, however, the magnitude and robustness of these effects have not been meta-analytically quantified. We conducted a systematic review and meta-analysis of estrous cycle effects on anxiety-like behaviour (124 articles; k = 259 effect sizes). In both rats and mice, anxiety-like behaviour was higher during metestrus/diestrus (lower ovarian hormones) than proestrus (higher ovarian hormones) (g = 0.44 in rats, g = 0.43 in mice). There was large heterogeneity in the data, which was partially accounted for by strain, experimental task, and reproductive status. Nonetheless, the effect of estrous cycle on anxiety-like behaviour was highly robust, with the fail-safe N test revealing the effect would remain significant even if 21,388 additional studies yielded null results. These results suggest that estrous cycle should be accounted for in studies of anxiety in females. Doing so will facilitate knowledge about menstrual-cycle regulation of anxiety disorders in humans.

A Vestibular Challenge Combined with Calcitonin Gene-Related Peptide (CGRP) Promotes Anxiety-Like Behaviors.

Motion-induced anxiety and agoraphobia are more frequent symptoms in patients with vestibular migraine (VM) than migraine without vertigo. The neuropeptide calcitonin gene-related peptide (CGRP) is a therapeutic target for migraine and VM, but the link between motion hypersensitivity, anxiety, and CGRP is relatively unexplored, especially in preclinical mouse models. To further examine this link, we tested the effects of systemic CGRP and off-vertical axis rotation (OVAR) on elevated plus maze (EPM) and rotarod performance in male and female C57BL/6J mice. Rotarod ability was assessed using two different dowel diameters: mouse dowel (r = 1.5 cm) versus rat dowel (r = 3.5 cm). EPM results indicate that CGRP alone or OVAR alone did not increase anxiety indices. However, the combination of CGRP and OVAR did elicit anxiety-like behavior. On the rotarod, CGRP reduced performance in both sexes on a mouse dowel but had no effect on a rat dowel, whereas OVAR had a significant effect on the rat dowel. These results suggest that only the combination of CGRP with vestibular stimulation induces anxiety-like behavior and that CGRP affects the dynamic balance function in mice depending on the type of challenge presented. These findings suggest that anxiety-like behaviors can be teased out from imbalance behaviors in a mouse model of "migraine." Future studies are aimed to determine if CGRP receptor antagonists that have been effective treating migraineurs and mouse "migraine" models may also reduce the anxiety observed in migraine.

The Dose-Dependent Effect of Fractionated γ-Radiation on Anxiety-Like Behavior in Neonatal Mice.

High doses of ionizing radiation are the risk factor of cognitive dysfunction and anxiety disorders developing in humans and experimental animals. However, the data on the effect of low doses, especially in case of chronic or fractionated exposure, is limited and contradictory. Here we studied the effect of fractionated γ-radiation at cumulative doses of 0.1, 1, and 5 Gy on the parameters of the anxiety-like behavior in neonatal C57BL/6 mice. The anxiety was evaluated using the marble burying test and elevated plus maze. Fractionated irradiation resulted in dose-dependent changes in mouse behavior: the low dose caused an increase in anxiety, wherein the dose raise led to the decrease in anxiety-like behavior indicators compared to non-irradiated animals.

The alpha1A antagonist tamsulosin impairs memory acquisition, consolidation and retrieval in a novel object recognition task in mice.

Tamsulosin is an α1-adrenoceptor antagonist used to treat benign prostatic hyperplasia. This drug exhibits high affinity for α1A- and α1D-adrenoceptor subtypes, which are also expressed in the brain. While dementia symptoms have been reported after administration of tamsulosin in humans, studies on its effects on the rodent brain are still rare. The present study investigated the effects of tamsulosin (and biperiden, an amnesic drug) on cognitive performance in the object recognition task (ORT). Tamsulosin (0.001-0.01 mg/kg) was orally administrated in mice at three distinct time points: pre-training, post-training and pre-test session. Tamsulosin 0.01 mg/kg impaired object recognition regardless of when it was injected, whereas at lower doses did not affect mouse performance in the ORT. Biperiden also impaired acquisition and consolidation of object recognition in mice. Furthermore, the effects of tamsulosin on locomotion, motivation and anxiety were excluded as potential confounding factors. At all doses tested, tamsulosin did not alter distance moved, time spent exploring objects in the ORT, and anxiety-related behaviors in the elevated plus-maze test. By contrast, diazepam evoked a significant reduction of anxiety-like behaviours. In conclusion, tamsulosin impaired memory acquisition, consolidation and retrieval in an object recognition task in mice, thus affecting memory performance in a non-specific phase manner. These findings contribute to our understanding of the potential adverse effects of tamsulosin, and shed light on the role played by α1-adrenoceptors, particularly α1A- subtype, in cognitive processes.

Anxiolytic-like effects of milk proteins.

Milk varieties and specific proteins exhibit anxiolytic-like actions in mice and rats exposed to several tests, the most prominent being the elevated plus-maze. Administrations of αs1-casein, its 91-100 (α-casozepine), 91-97, 91-93, and 91-92 fragments, the 60-69 fragment of ß-casein, lactoferrin, ß-lactotensin, wheylin-1, wheylin-2, and α-lactalbumin have been reported to increase open arm exploration relative to enclosed arm exploration. Anxiolytic-like actions have also been described for 91-93 and 91-92 fragments of αs1-casein, wheylin-1, α-lactalbumin, and lactoferrin in the open-field. Some effects appear to be mediated by the GABAA receptor complex, since antagonists mitigated the anxiolytic-like actions of αs1-casein, the 91-92 fragment of αs1-casein, and wheylin-1. Other neurotransmitters purported to affect such behaviors include 5HT, dopamine, and neurotensin. Further research is needed to identify their neuropharmacological actions.

Catechin Protects against Lipopolysaccharide-induced Depressive-like Behaviour in Mice by Regulating Neuronal and Inflammatory Genes.

BACKGROUND: Many studies have suggested that tea has antidepressant effects; however, the underlying mechanism is not fully studied. As the main anti-inflammatory polyphenol in tea, catechin may contribute to the protective role of tea against depression. OBJECTIVE: The objective of this study is to prove that catechin can protect against lipopolysaccharide (LPS)-induced depressive-like behaviours in mice, and then explore the underlying molecular mechanisms. METHODS: Thirty-one C57BL/6J mice were categorized into the normal saline (NS) group, LPS group, catechin group, and amitriptyline group according to their treatments. Elevated Plus Maze (EPM), Tail Suspension Test (TST), and Open Field Test (OFT) were employed to assess depressive- like behaviours in mice. RNA sequencing (RNA-seq) and subsequent Bioinformatics analyses, such as differential gene analysis and functional enrichment, were performed on the four mouse groups. RESULTS: In TST, the mice in the LPS group exhibited significantly longer immobility time than those in the other three groups, while the immobility times for the other three groups were not significantly different. Similarly in EPM, LPS-treated mice exhibited a significantly lower percentage in the time/path of entering open arms than the mice in the other three groups, while the percentages of the mice in the other three groups were not significantly different. In OFT, LPS-treated mice exhibited significantly lower percentages in the time/path of entering the centre area than those in the other three groups. The results suggested that the LPS-induced depression models were established successfully and catechin can reverse (LPS)-induced depressive-like behaviours in mice. Finally, RNA-seq analyses revealed 57 differential expressed genes (DEGs) between LPS and NS with 19 up-regulated and 38 down-regulated. Among them, 13 genes were overlapped with the DEGs between LPS and cetechin (in opposite directions), with an overlapping p-value < 0.001. The 13 genes included Rnu7, Lcn2, C4b, Saa3, Pglyrp1, Gpx3, Lyz2, S100a8, S100a9, Tmem254b, Gm14288, Hbb-bt, and Tmem254c, which might play key roles in the protection of catechin against LPS-induced depressive-like behaviours in mice. The 13 genes were significantly enriched in defense response and inflammatory response, indicating that catechin might work through counteracting changes in the immune system induced by LPS. CONCLUSION: Catechin can protect mice from LPS-induced depressive-like behaviours through affecting inflammatory pathways and neuron-associated gene ontologies.

Behavior, antioxidant, and metabolomics effects of Allium tuncelianum.

Allium species are consumed extensively as folkloric medicine and dietary elements, but limited studies have been conducted on them. In this study, the effects of an ethanol-water extract obtained from the underground bulb of Allium tuncelianum (Kollmann) Özhatay, B. Mathew & Siraneci (AT) on the behavioral, antioxidant, and metabolite parameters in rats were evaluated. AT was administered orally once a day at doses of 100 and 400 mg/kg to male Wistar albino rats for 10 consecutive days. The elevated plus maze, rotarod, and hotplate tests were used to examine anxiety-like behaviors, locomotor activities, and pain perception in the rats, respectively. Additionally, untargeted metabolomic analyses were performed on plasma samples and AT extracts using two orthogonal analytical platforms. The phenolic components, mainly fumaric acid, malic acid, vanillic acid, quercetin-3-arabinoside, hydrocinnamic acid, and gallocatechin, were determined in the extract. In addition, arbutin, salicylic acid, trehalose, and nicotinic acid were analyzed in the extract for the first time. The AT extract did not decrease the catalase, glutathione peroxidase, or superoxide dismutase levels; however, diazepam decreased some of those parameters significantly in the brain, liver, and kidney. Although both the AT and diazepam treatments resulted in an increase in anxiolytic-like effects compared to the control group, no significant differences were observed (p > .05). In the metabolomic analysis, significant changes were observed in the rats treated with AT and diazepam, and they caused significant changes in some metabolic pathways, including amino acid and fatty acid metabolism, compared to the control.

Elevated Plus Maze for Assessment of Anxiety and Memory in Rodents.

The elevated plus maze is the most widely used paradigm to evaluate anxiety-associated behavioral alterations in rodent models of central nervous system (CNS) disorders. Unconditioned aversive behavior for open and elevated areas is a measure of anxiety and can be assessed by the plus maze. Plus maze consists of perpendicularly arranged open arms and closed arms crossed in the middle with a central platform. Rodents are allowed to explore the maze between the open and closed arms. The number of entries and time spent in the open arms and the closed arms are used as indicators for the anxiety nature of the animals. Transfer latency is a memory indicator that measures the amount of time it takes to move an animal from an open arm to a closed arm. This chapter describes the pretest conditions, materials required, and protocol for the conductance and evaluating the results for the anxiety and cognition-related behavior in rodents.

Centella asiatica improves memory and executive function in middle-aged rats by controlling oxidative stress and cholinergic transmission.

ETHNOPHARMACOLOGICAL RELEVANCE: Centella asiatica (L.) Urban, is a medicinal herb with rich history of traditional use in Indian subcontinent. This herb has been valued for its diverse range of medicinal properties including memory booster, and also as a folk treatment for skin diseases, wound healing and mild diuretic. AIM OF STUDY: Aging is a gradual and continuous process of natural decay in the biological systems, including the brain. This work aims to evaluate the effectiveness of ethanolic extract of Centella asiatica (CAE) on age-associated cognitive impairments in rats, as well as the underlying mechanism. MATERIAL AND METHODS: Rats were allocated into five distinct groups of 5 animals each: Young rats (3 months old rats), middle-aged (m-aged) rats (13-14 months old), and the remaining three groups were comprised of m-aged rats treated with different concentrations of CAE, viz., 150, 300, and 450 mg/kg b. w., orally for 42 days. Y-maze, open field, novel object recognition, and elevated plus maze tests were used to assess animal behavior. The malondialdehyde (MDA), superoxide dismutase (SOD), and acetylcholinesterase (AChE) assays; and H&E staining were done in the rat brain to assess the biochemical and structural changes. CAE was also subjected to HPLC analysis, in vitro antioxidant and anti-cholinergic activity. The active compounds of CAE were docked with AChE and BuChE in molecular docking study. RESULTS: The results showed that CAE treatment improves behavioral performance; attenuates the age-associated increase in MDA content, SOD, and AChE activity; and reduces neuronal loss. In vitro study showed that CAE has concentration-dependent antioxidant and anti-AChE activity. Furthermore, the presence of Asiatic acid and Madecassic acid in CAE and their good binding with cholinergic enzymes (in silico) also suggest the anticholinergic effect of CAE. CONCLUSION: The findings of the current study show that the anticholinergic and antioxidant effects of CAE are attributable to the presence of Asiatic acid and Madecassic acid, which not only provide neuroprotection against age-associated cognitive decline but also reverse it.

New curcumin-loaded nanocapsules as a therapeutic alternative in an amnesia model.

This study aimed to investigate the action of two different formulations of curcumin (Cur)-loaded nanocapsules (Nc) (Eudragit [EUD] and poly (ɛ-caprolactone) [PCL]) in an amnesia mice model. We also investigated the formulations' effects on scopolamine-induced (SCO) depressive- and anxiety-like comorbidities, the cholinergic system, oxidative parameters, and inflammatory markers. Male Swiss mice were randomly divided into five groups (n = 8): group I (control), group II (Cur PCL Nc 10 mg/kg), group III (Cur EUD Nc 10 mg/kg), group IV (free Cur 10 mg/kg), and group V (SCO). Treatments with Nc or Cur (free) were performed daily or on alternate days. After 30 min of treatment, the animals received the SCO and were subjected to behavioral tests 30 min later (Barnes maze, open-field, object recognition, elevated plus maze, tail suspension tests, and step-down inhibitory avoidance tasks). The animals were then euthanized and tissue was removed for biochemical assays. Our results demonstrated that Cur treatment (Nc or free) protected against SCO-induced amnesia and depressive-like behavior. The ex vivo assays revealed lower acetylcholinesterase (AChE) and catalase (CAT) activity, reduced thiobarbituric species (TBARS), reactive species (RS), and non-protein thiols (NSPH) levels, and reduced interleukin-6 (IL-6) and tumor necrosis factor (TNF) expression. The treatments did not change hepatic markers in the plasma of mice. After treatments on alternate days, Cur Nc had a more significant effect than the free Cur protocol, implying that Cur may have prolonged action in Nc. This finding supports the concept that it is possible to achieve beneficial effects in nanoformulations, and treatment on alternate days differs from the free Cur protocol regarding anti-amnesic effects in mice.

Long-term effects of neonatal pain and sucrose treatment.

Purpose: In neonatal intensive care units, applying sucrose solution for analgesia is now a routine treatment for mild procedural pain. Studies of animal and human infants provide clear evidence of benefits in the short term, but few studies have investigated the long term benefits. Thus, we determined whether sucrose could ameliorate painful stimulation during infancy in Sprague-Dawley rats and also explored the long-term effects of repeated sucrose administration during infancy. Female and male rats were included to investigate sex-related differences. Methods: Rat pups were stimulated either with painful or tactile stimuli for the first 14 days of their lives. Pups were pretreated either with sucrose or not treated before stimulation. Behavioral tests were conducted during adolescence and adulthood. Hotplate, rotarod, open field, elevated plus maze, and radial arm water maze tests were employed to assess the behavioral consequences of early life manipulations and treatments. Results: Painful stimulation during infancy increased the sensitivity to pain later in life, and sucrose did not remedy this effect. Motility, coordination, anxiety, and cognition tests in adulthood obtained mixed results. Pain during infancy appeared to increase anxiety during adulthood. Learning and memory in adulthood were affected by pain during infancy, and sucrose had a negative effect even in the absence of pain. No sex-related differences were observed in any of the behavioral tests by employing this model of neonatal pain. Conclusion: Painful stimulation during infancy resulted in deficiencies in some behavioral tests later in life. Sucrose pretreatment did not mitigate these shortcomings and it actually resulted in negative outcomes.

Structural consistency of exploratory behaviour of sub-adult and adult spiny mice (Acomys cahirinus) in seven different tests.

The genus Acomys is of growing importance to many research fields. Previous research has shown that individuals differ when exploring new environments and that these behavioural strategies are consistent in time. In this study, we subjected 60 commensal Acomys cahirinus (37 males, 23 females) to a series of seven tests (free exploration, forced exploration under bright illumination, forced exploration under low illumination, hole board test, vertical activity test, elevated plus maze, and voluntary wheel running) to acquire independent behavioural traits and investigate whether and how personality develops in spiny mice. The full series of experiments was performed twice during ontogeny: once in the sub-adult stage (tested at 62-72 days of age) and once in the adult stage (102-112 days of age). We found that behaviour of the animals was repeatable both within (range of R values from 0.155 to 0.726) and across the two life-stages (0.238 to 0.563). While the structure of behaviour in adults was rather clear, it had not been fully crystalized in sub-adults, suggesting personality changes during maturation, even though some individual traits might be repeatable across ontogeny. Notably, the most consistent behavioural traits across the different tests were jumping and rearing, which are not commonly reported.

Gestational environmental enrichment prevents chronic social stress induced anxiety- and ethanol-related behaviors in offspring.

Epidemiological surveys have shown a strong relationship between maternal stress and offspring's mood disorders. Growing evidence suggested that environmental enrichment (EE) improves cognitive function in models of psychiatric and neurological disorders. However, the potential protective effects of gestational EE on social stress-elicited mood disorders in offspring have not been studied. Knowing that the undeveloped brain is more sensitive to gestational environmental stimuli, we hypothesized that initiating cognitive stimulation, during gestation, would protect against social stress-induced behavioral alterations in adulthood. Therefore, the present study aimed to investigate the effects of gestational EE on social stress-elicited anxiety- and ethanol-related behaviors in adult offspring. EE consisted of free access, of dams, to tubular devices of different shapes, colors, and sizes that were changed regularly. After birth and weaning, young adult offspring were exposed to 19 days of social stress and anxiety-like behavior was evaluated by elevated plus maze, open field, and marbles burying tests. The two-bottle choice (TBC) drinking paradigm was used to assess stress-induced ethanol intake. Results showed that gestational EE prevented social stress-elicited anxiogenic-like effects with no differences in spontaneous locomotor activity. Moreover, in the TBC paradigm, mice pre-exposed to EE consistently showed a significantly decreased consumption and preference for ethanol with no effects on tastants' intakes. Interestingly, gestational EE increased serum BDNF levels, which showed a correlation with measures of anxiety- and ethanol-related behaviors. These findings indicate that some neurodevelopmental changes associated with prenatal EE may counteract adult social stress-induced behavioral alterations through a BDNF mechanism. Therefore, we propose that gestational EE has significant protective and beneficial effects on social stress-induced cognitive impairment. It can also alleviate anxiety-like behavior and subsequent excessive alcohol consumption.

Subregion specific neuroadaptations in the female rat striatum during acute and protracted withdrawal from nicotine.

Epidemiological studies and clinical observations suggest that nicotine, a major contributor of the global burden of disease, acts in a partially sex specific manner. Still, preclinical research has primarily been conducted in males. More research is thus required to define the effects displayed by nicotine on the female brain. To this end, female rats received 15 injections of either nicotine (0.36mg/kg) or saline, over a 3-week period and were then followed for up to 3 months. Behavioral effects of nicotine were assessed using locomotor activity measurements and elevated plus maze, while neurophysiological changes were monitored using ex vivo electrophysiological field potential recordings conducted in subregions of the dorsal and ventral striatum. Behavioral assessments demonstrated a robust sensitization to the locomotor stimulatory properties of nicotine, but monitored behaviors on the elevated plus maze were not affected during acute (24 h) or protracted (3 months) withdrawal. Electrophysiological recordings revealed a selective increase in excitatory neurotransmission in the nucleus accumbens shell and dorsomedial striatum during acute withdrawal. Importantly, accumbal neuroadaptations in nicotine-treated rats correlated with locomotor behavior, supporting a role for the nucleus accumbens in behavioral sensitization. While no sustained neuroadaptations were observed following 3 months withdrawal, there was an overall trend towards reduced inhibitory tone. Together, these findings suggest that nicotine produces selective transformations of striatal brain circuits that may drive specific behaviors associated with nicotine exposure. Furthermore, our observations suggest that sex-specificity should be considered when evaluating long-term effects by nicotine on the brain.

Forty-kHz ultrasonic vocalizations of rat pups predict adult behavior in the elevated plus-maze behavior but not the effect of cocaine on 50-kHz ultrasonic vocalizations.

Ultrasonic vocalizations (USV) are emitted by both young pups and adult rats to convey positive or negative emotional states. These USV manifestations are contingent on factors including developmental stage, situational requirements, and individual dispositions. Pups emit 40-kHz USV when separated from their mother and litter, which function to elicit maternal care. Conversely, adult rats can produce 50-kHz USV in response to stimuli that elicit reward-related states, including natural rewards, stimulant drugs, and reward-predictive stimuli. The present study aims to investigate whether pup 40-kHz USV can serve as predictors of behaviors related to positive or negative states in adult rats. Both male and female Wistar pups were initially tested on the 11th postnatal day and subsequently in adulthood. There was no significant difference in the number of 40-kHz ultrasonic vocalizations between male and female pups. However, cocaine elicited more 50-kHz USV and hyperactivity in adult females compared to males. Notably, cocaine increased the proportion of step and trill USV subtypes in both adult males and females. Interestingly, this effect of cocaine was stronger in females that were in the diestrus, compared to the estrus phase. In males, a significant positive correlation was found between pup 40-kHz USV and lower anxiety scores in adult male but not female rats tested on the elevated plus-maze test. Furthermore, no significant correlation was found between pup 40-kHz and adult 50-kHz USV in both males and females, whether in undrugged (saline) or in cocaine-treated rats. It is possible that the 40-kHz USV emitted by pups predicted reduced anxiety-like behavior only for male rats because they could elicit maternal care directed specifically to male pups. These findings suggest that 40-kHz USV can serve as an indicator of the emotional link between the rat mother and male pups. Indeed, this suggests that maternal care exerts a positive influence on the emotional state during adulthood.

The effect of acute and chronic formaldehyde exposure on learning and memory in male and female rats.

AIM: Formaldehyde is a chemical that lies behind the various systemical failures in organism. Many products that people use contain formaldehyde. Owing to its tissue fixative properties, scientists who work in life sciences are exposed to this substance more than others. Several studies have shown that formaldehyde affects the CA1 and CA3 regions of the hippocampus, which play crucial roles in memory consolidation. In this study, we aimed to investigate anxiety levels and indicate the short and long term effects of formaldehyde and sex-related differences by exposing formaldehyde to male and female rats. MATERIALS AND METHODS: Formaldehyde (10 mg/kg) was administered intraperitoneally for 7 days for acute exposure and 30 days for chronic exposure. Cognitive assessment was performed using fear conditioning, elevated plus maze, and Morris water maze tests. TUNEL staining was used to identify apoptosis in the brains obtained after decapitation. RESULTS: Exposure to intraperitoneal formaldehyde does not impair learning and memory in acute and chronic periods and has no effect on depression or anxiety. After acute exposure, apoptosis was observed in the hippocampal CA1 and CA3 regions in males. When the cognitive test results were examined, no differences were found between the experimental and control groups. There was also no significant difference between males and females.

Possible involvement of GABAergic system on central amygdala Mediated anxiolytic effect of agmatine in rats.

OBJECTIVES: To study the pharmacological interactions between agmatine and gamma aminobutyric acid (GABA) modulatory agents in the regulation of anxiety-like behavior in rats. MATERIALS AND METHODS: Male Wistar rats were treated drugs per se or in combination and 15 min after last injection were subjected to elevated plus-maze (EPM) test. Anxiety-like behavior was evaluated by measuring behavioral conventional readout, open arm activity (duration and/or entries) for 5-minute duration. RESULTS: Acute intra-central amygdala (CeA) injection of agmatine (0.1-0.6 µmol/site/rat), muscimol (0.25-1 nmol/site/rat), diazepam (5-20 µg/site/rat) and allopregnanolone (2-8 µg/site/rat) increased open arm entries of the rats in EPM suggesting anxiolytic effect in dose dependent manner. Moreover, the anxiolytic effect at subeffective dose of agmatine (0.1 µmol/site/rat) was potentiated by subeffective dose of muscimol (0.25 nmol/site/rat), diazepam (5 µg/site/rat) and allopregnanolone (4 µg/site/rat). Whereas, pretreatment with GABAA receptor antagonist, bicuculline (10 ng/site/rat) blocked the anxiolytic effect of agmatine and its synergistic effect of agmatine plus muscimol. Similarly, benzodiazepine (BZD) receptor antagonist, flumazenil (15 µg/site/rat) and GABA allosteric modulator antagonist, RO 15-45 13 (10 µg/site/rat) reduced the anxiolytic effect of agmatine, given alone and with diazepam and allopregnanolone, respectively. CONCLUSION: These results indicated that anxiolytic effect of agmatine is medicated via GABAergic mechanisms, probably conciliated by the GABAA receptor subtypes. Modulation of interplay between agmatine and GABAA receptor activity might be a pertinent solution for the regulation of anxiety.

Sex differences in avoidance behavior and cued threat memory dynamics in mice: Interactions between estrous cycle and genetic background.

Anxiety disorders are the most prevalent mental illnesses worldwide, exhibit high heritability, and affect twice as many women as men. To evaluate potential interactions between genetic background and cycling ovarian hormones on sex differences in susceptibility to negative valence behaviors relevant to anxiety disorders, we assayed avoidance behavior and cued threat memory dynamics in gonadally-intact adult male and female mice across four common inbred mouse strains: C57Bl/6J, 129S1/SVlmJ, DBA/2J, and BALB/cJ. Independent of sex, C57Bl/6J mice exhibited low avoidance but high threat memory, 129S1/SvlmJ mice high avoidance and high threat memory, DBA/2J mice low avoidance and low threat memory, and BALB/cJ mice high avoidance but low threat memory. Within-strain comparisons revealed reduced avoidance behavior in the high hormone phase of the estrous cycle (proestrus) compared to all other estrous phases in all strains except DBA/2J, which did not exhibit cycle-dependent behavioral fluctuations. Robust and opposing sex differences in threat conditioning and extinction training were found in the C57Bl/6J and 129S1/SvlmJ lines, whereas no sex differences were observed in the DBA/2J or BALB/cJ lines. C57Bl/6J males exhibited enhanced acute threat memory, whereas 129S1/SvlmJ females exhibited enhanced sustained threat memory, compared to their sex-matched littermates. These effects were not mediated by estrous cycle stage or sex differences in active versus passive defensive behavioral responses. Our data demonstrate that core features of behavioral endophenotypes relevant to anxiety disorders, such as avoidance and threat memory, are genetically driven yet dissociable and can be influenced further by cycling ovarian hormones.

Innate colour preference in zebrafish (Danio rerio).

Innate (natural) colour preference in animals is used for a variety of behavioural neuroscience purposes in many animal models. In zebrafish, colour preference is often used in combination with place preference testing and some memory tests. However, baseline colour preference seems to differ in the few studies examining this innate behaviour. This necessitates a protocol for reliable colour preference testing to establish preferences prior to using more complex behavioural paradigms. This procedure involves an aquatic plus maze with a central neutral zone and 4 coloured zones: red, green, yellow, blue. Adult zebrafish spent significantly more time in the blue zone compared to the red and yellow zones. There were no sex differences in colour preference. This procedure is a rapid, affordable, straightforward, and effective method to establish baseline colour preference.