Anxiogenic effects of methyl-beta-carboline-3-carboxylate in a light/dark choice situation

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 β-casein, lactoferrin, β-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.

Effects of low doses of the novel dehydroepiandrosterone (DHEA) derivative BNN27 in rat models of anxiety

RATIONALE

Several lines of evidence indicate that the neurosteroid dehydroepiandrosterone (DHEA) is involved in anxiety. BNN27 is a new DHEA derivative lacking steroidogenic effects. The beneficial effects exerted by BNN27 in preclinical models of schizophrenia and memory disorders have been recently reported.

OBJECTIVES

The present study was designed to investigate the effects of this DHEA novel analog on anxiety-like behavior in rats.

METHODS

To this end, the light/dark box, the open field, the contextual fear conditioning, and the excessive self-grooming induced by the serotonin 5-HT2c receptor agonist mCPP tests were utilized.

RESULTS

Animals treated acutely with BNN27 (1, 3, and 6 mg/kg) dose dependently spent more time in the bright compartment of the light/dark box and in the central zone of the open field with respect to their vehicle-treated cohorts. Further, BNN27 reduced freezing behavior and weakened the mCPP-induced excessive self-grooming.

CONCLUSIONS

Our data indicate that BNN27 is a highly potent anxiolytic agent, as in all studied paradigms it showed anxiolytic-like effects in male rats.

The GABAA-Benzodiazepine Receptor Antagonist Flumazenil Abolishes the Anxiolytic Effects of the Active Constituents of Crocus sativus L. Crocins in Rats

Anxiety is a chronic severe psychiatric disorder. Crocins are among the various bioactive components of the plant Crocus sativus L. (Iridaceae) and their implication in anxiety is well-documented. However, which is the mechanism of action underlying the anti-anxiety effects of crocins remains unknown. In this context, it has been suggested that these beneficial effects might be ascribed to the agonistic properties of these bioactive ingredients of saffron on the GABA type A receptor. The current experimentation was undertaken to clarify this issue in the rat. For this research project, the light/dark and the open field tests were used. A single injection of crocins (50 mg/kg, i.p., 60 min before testing) induces an anti-anxiety-like effect revealed either in the light-dark or open field tests. Acute administration of the GABA_A-benzodiazepine receptor antagonist flumazenil (10 mg/kg, i.p., 30 min before testing) abolished the above mentioned anxiolytic effects of crocins. The current findings suggest a functional interaction between crocins and the GABA_A receptor allosteric modulator flumazenil on anxiety.

Metabolic and psychiatric effects of acyl coenzyme A binding protein (ACBP)/diazepam binding inhibitor (DBI)

Acyl coenzyme A binding protein (ACBP), also known as diazepam binding inhibitor (DBI) is a multifunctional protein with an intracellular action (as ACBP), as well as with an extracellular role (as DBI). The plasma levels of soluble ACBP/DBI are elevated in human obesity and reduced in anorexia nervosa. Accumulating evidence indicates that genetic or antibody-mediated neutralization of ACBP/DBI has anorexigenic effects, thus inhibiting food intake and inducing lipo-catabolic reactions in mice. A number of anorexiants have been withdrawn from clinical development because of their side effects including an increase in depression and suicide. For this reason, we investigated the psychiatric impact of ACBP/DBI in mouse models and patient cohorts. Intravenously (i.v.) injected ACBP/DBI protein conserved its orexigenic function when the protein was mutated to abolish acyl coenzyme A binding, but lost its appetite-stimulatory effect in mice bearing a mutation in the γ2 subunit of the γ-aminobutyric acid (GABA) A receptor (GABA_AR). ACBP/DBI neutralization by intraperitoneal (i.p.) injection of a specific mAb blunted excessive food intake in starved and leptin-deficient mice, but not in ghrelin-treated animals. Neither i.v. nor i.p. injected anti-ACBP/DBI antibody affected the behavior of mice in the dark–light box and open-field test. In contrast, ACBP/DBI increased immobility in the forced swim test, while anti-ACBP/DBI antibody counteracted this sign of depression. In patients diagnosed with therapy-resistant bipolar disorder or schizophrenia, ACBP/DBI similarly correlated with body mass index (BMI), not with the psychiatric diagnosis. Patients with high levels of ACBP/DBI were at risk of dyslipidemia and this effect was independent from BMI, as indicated by multivariate analysis. In summary, it appears that ACBP/DBI neutralization has no negative impact on mood and that human depression is not associated with alterations in ACBP/DBI concentrations.

Overview on Emotional Behavioral Testing in Rodent Models of Pediatric Epilepsy

Psychiatric and cognitive disturbances are the most common comorbidities of epileptic disorders in children. The successful treatment of these comorbidities faces many challenges including their etiologically heterogonous nature. Translational neurobehavioral research in age-tailored and clinically relevant rodent seizure models offers a controlled setting to investigate emotional and cognitive behavioral disturbances, their causative factors, and potentially novel treatment interventions. In this review, we propose a conceptual framework that provides a nonsubjective approach to rodent emotional behavioral testing with a focus on the clinically relevant outcome of behavioral response adaptability. We also describe the battery of neurobehavioral tests that we tailored to seizure models with prominent amygdalo-hippocampal involvement, including testing panels for anxiety-like, exploratory, and hyperactive behaviors (the open-field and light-dark box tests), depressive-like behaviors (the forced swim test), and visuospatial navigation (Morris water maze). The review also discusses the modifications we introduced to active avoidance testing in order to simultaneously test auditory and hippocampal-dependent emotionally relevant learning and memory. When interpreting the significance and clinical relevance of the behavioral responses obtained from a given testing panel, it is important to avoid a holistic disease-based approach as a specific panel may not necessarily mirror a disease entity. The analysis of measurable behavioral responses has to be performed in the context of outcomes obtained from multiple related and complementary neurobehavioral testing panels. Behavioral testing is also complemented by mechanistic electrophysiological and molecular investigations.

Repeated but not acute exposure with a low dose range of the nitric oxide (NO) donor sodium nitroprusside (SNP) induces anxiolytic-like behaviour in a dose-independent manner in two different rat models of anxiety

Sodium nitroprusside (SNP) is a nitric oxide (NO) donor which actually is under assessment as a potential candidate for the treatment of schizophrenia. It is well documented that anxiety symptoms are a prominent future in various psychiatric diseases comprising schizophrenia. Prior research has shown that acute challenge with SNP (1-3 mg/kg) induced anti-anxiety effects in rats but these effects at high doses were confounded by sedation and were disappeared after repeated application of it. It is still unknown if administration of a lower SNP dose range, either acutely or sub-chronically, could induce anxiolytic-like behaviour. The present study was designed to investigate this issue in rats. For this aim, the light/dark and the open field tests were used. Acute challenge with SNP (0.1 and 0.3 mg/kg, 30 min before testing) did not affect rodents' performance in the above mentioned behavioural paradigms. Conversely, rats treated sub-chronically with SNP (0.1 and 0.3 mg/kg, once per day, for 5 consecutive days), displayed longer time spent in the light chamber of the light/dark box and in the central area of the open field with respect to their vehicle-treated counterparts. Interestingly, SNP did not influence the first latency to enter the dark chamber and the number of transitions between the light and dark compartments of the apparatus in the light/dark test and did not modify the number of squares crossed, grooming episodes and rearings in the open field test. Finally, acute administration of SNP (0.1, 0.3 and 1 mg/kg, 10 min before testing) also did not influence rats' performance in the light/dark test. The present results indicate that short-term repeated but not acute application of a range of low doses of the NO donor SNP in a dose-independent manner induced an anti-anxiety behaviour in the rat which was not accompanied by undesired effects.

Evidence for the involvement of a GABAergic mechanism in the effectiveness of natural and synthetically modified incensole derivatives in neuropharmacological disorders: A computational and pharmacological approach

In the course of our continuing exploration for novel bioactive lead compounds (s) from the species Boswellia, we have recently reported incensole derivatives isolated from Boswellia papyrifera Hochst. Given the known antidepressant-like effects of incensole and incensole acetate, we herein present that the low dose intraperitoneal administration of incensole derivatives, namely, incensfuran and incensone, showed significant antidepressant-like effects in the forced swim test (FST) and tail suspension test (TST). Furthermore, these compounds were evaluated for their anxiolytic potential in the elevated plus maze (EPM) and light dark box (LDB) tests and anticonvulsant effects in pentylenetetrazole (PTZ)-induced seizure tests. In the EPM test, administration of these compounds led to dose-dependent increases in open arm entries and in the time spent in EPM open arms. Similar results were obtained in the LDB test, wherein compounds these caused significant increases in the number of transitions between lit and dark compartments and the time spent in the lit compartment. The anxiolytic-like effects in the EPM were not reversed by pretreatment with flumazenil, whereas PTZ and bicuculline (BIC) completely abolished the anxiolytic effects, showing the involvement of the non-benzodiazepine binding sites of GABA_A receptors. All four compounds induced significantly elevated brain GABA levels, indicating the involvement of a GABAergic mechanism. Additionally, molecular docking was conducted to elucidate the mode of action for the anxiolytic and anticonvulsant effects of these derivatives. Moreover, these compounds also possess drug-like properties and excellent ADMET profiles.

Effects of Anesthetic Ketamine on Anxiety-Like Behaviour in Rats

There is scarce information regarding the effects of anesthetic doses of the non-competitive N-methyl-D-aspartate receptor antagonist ketamine on anxiety. The current study evaluated the acute effects of intraperitoneally (i.p.) administered anesthetic ketamine (100 mg/kg) i.p. on anxiety in rats. For this purpose, the light/dark and the open field tests were utilized. The effects of anesthetic ketamine on motility were also examined using a motility cage. In the light/dark test, anesthetic ketamine, administered 24 h before testing reduced the number of transitions between the light and dark compartments and the time spent in the light compartment in the rats compared with their control cohorts. In addition, ketamine was found to exert a depressive effect on rats' motility. In the open field test, animals treated with anesthetic ketamine 24 h before testing spent essentially no time in the central area of the apparatus, decreased horizontal ambulatory activity, and preserved to a certain extent their exploratory behaviour compared to their control counterparts. The results suggest that, in spite of its hypokinetic effect, a single anesthetic ketamine administration apparently induces an anxiety-like state, while largely preserving exploratory behaviour in the rat. These effects were time-dependent they since they were extinguished when testing was carried out 48 h after anesthetic ketamine administration.

The Open Field Test for Measuring Locomotor Activity and Anxiety-Like Behavior

The open field test is used in studies of the neurobiological basis of anxiety and screening for novel drug targets and anxiolytic compounds. This test uses a camera to measure movement of the test animal in the peripheral and central zones of a 42 × 42 × 42 cm polyvinyl chloride box. This chapter describes a protocol for carrying out the open-field test for assessment of locomotion and anxiety-like behavior in mice.

Isolation and Characterization of Two New Secondary Metabolites From Quercus incana and Their Antidepressant- and Anxiolytic-Like Potential

The ethyl acetate fraction of Quercus incana yielded two new compounds [1 and 2]. The characterization and structure elucidation of these compounds were carried out through various spectroscopic techniques such as mass spectrometry along with one- and two-dimensional NMR techniques. The structural formula was deduced to be 2-(4-hydroxybutan-2-yl)-5-methoxyphenol [1] and 4-hydroxy-3-(hydroxymethyl) pentanoic acid [2]. The elevated plus maze (EPM) and light–dark box (LDB) tests (classical mouse models) were performed in order to reveal the anxiolytic potential of both compounds [1 and 2]. Both compounds displayed dose-dependent increases in open-arm entries and time spent in open arms in EPM (^∗P < 0.05, ^∗∗P < 0.01), and increased the time spent in the lit compartment and increased transitions between the two compartments in LDB test (^∗P < 0.05, ^∗∗P < 0.01). Co-administration of selective benzodiazepine (BZP) receptor antagonist, flumazenil (2.5 mg/kg) with compounds [1 and 2] decreased the anxiolytic-like activity of both compounds in the EPM indicating BZP-binding site of GABA-A receptors are involved in the anxiolytic-like effect. Similarly, both compounds at the dose level of 10 and 30 mg/kg, i.p. exerted pronounced antidepressant-like effect in both forced swimming as well as tail suspension tests (^∗P < 0.05, ^∗∗P < 0.01; ANOVA followed by Dunnett’s post hoc test). The effect at 30 mg/kg was comparable to the reference drug imipramine (60 mg/kg).

Extracellular regulated protein kinaseis critical for the role of 5-HT1a receptor in modulating nNOS expression and anxiety-related behaviors

Our previous study found that serotonin 1A receptor (5-HT1aR) is an endogenous suppressor of nNOS expression in the hippocampus, which accounts for anxiolytic effect of fluoxetine. However, the precise molecular mechanism remains unknown. By using 8-OH-DPAT, a selective 5-HT1aR agonist, NAN-190, a selective 5-HT1aR antagonist, and U0126, an Extracellular Regulated Protein Kinases (ERK) phosphorylation inhibitor, we investigated the role of ERK in 5-HT1aR-nNOS pathway. Western blots analysis demonstrated that 5-HT1aR activation up-regulated the level of phosphorylated ERK (P-ERK) beginning at 5 min and down-regulated the expression of nNOS beginning at 20 min. Meanwhile, blockage of 5-HT1aR resulted in a decrease in P-ERK beginning at 20 min and caused an increase in nNOS expression beginning at 6 h. Although U0126 itself did not alter nNOS expression and activity, NO level, and anxiety-related behaviors, the treatment totally reversed 8-OH-DPAT-induced reduction in nNOS expression and function, and anxiolytic effect. Besides, our data showed that ERK phosphorylation was essential for 5-HT1aR activation-induced cAMP responsive element binding protein (CREB) phosphorylation, hippocampal neurogenesis and synaptogenesis of newborn neuron. Our study suggests a crucial role of ERK phosphorylation in the regulation of nNOS expression by 5-HT1aR, which is helpful for understanding the mechanism of 5-HT1aR-based anxiolytic treatment.

Anticonvulsant, Anxiolytic, and Sedative Activities of Verbena officinalis

We describe different neuropharmacological effects of Verbena officinalis crude extract (Vo.Cr). Pentylenetetrazole (PTZ)-induced seizures, elevated plus maze, light-dark box (LDB), open field and thiopental-induced sleeping test models were employed to evaluate Vo.Cr actions in mice. Vo.Cr dose-dependently (100-500 mg/Kg) delayed onset time of myoclonic jerks and tonic-clonic seizures, while decreased duration of tonic-clonic seizures (P < 0.05, P < 0.001 vs. saline group). Vo.Cr at 100 and 300-500 mg/Kg doses reduced animals' mortality in PTZ-induced seizures test to 75 and 0%, respectively. Vo.Cr (50-300 mg/Kg) significantly increased time spent and number of entries into open arms, while decreased time spent and number of entries into closed arms (P < 0.05, P < 0.01, P < 0.001 vs. saline group), measured in elevated plus maze. Vo.Cr (50-300 mg/Kg) increased time spent in light compartment, while decreased time spent in dark compartment (P < 0.01, P < 0.001 vs. saline group) in LDB, like caused by diazepam. In open field test, Vo.Cr decreased number of ambulations and rearings frequencies, while increased the number of central squares crossings. In thiopental-induced sleeping test, Vo.Cr (50-300 mg/Kg) decreased onset time of sleep, while increased the duration of sleep (P < 0.05, P < 0.01, P < 0.001 vs. saline group). These results indicate that Verbena officinalis possess anticonvulsant, anxiolytic and sedative activities, which provides scientific background for its medicinal application in various neurological ailments, such as epilepsy, anxiety, and insomnia.

The nitric oxide donor sodium nitroprusside attenuates recognition memory deficits and social withdrawal produced by the NMDA receptor antagonist ketamine and induces anxiolytic-like behaviour in rats

RATIONALE

Experimental evidence indicates that the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine impairs cognition and can mimic certain aspects of positive and negative symptoms of schizophrenia in rodents. Nitric oxide (NO) is considered as an intracellular messenger in the brain, and its abnormalities have been linked to schizophrenia.

OBJECTIVES

The present study was designed to investigate the ability of the NO donor sodium nitroprusside (SNP) to counteract schizophrenia-like behavioural deficits produced by ketamine in rats.

METHODS

The ability of SNP to reverse ketamine-induced memory deficits and social withdrawal were assessed using the novel object recognition task (NORT) and the social interaction test, respectively. Furthermore, since anxiety disorders are noted to occur commonly in schizophrenics, the effects of SNP on anxiety-like behaviour were examined using the light/dark test. Locomotor activity was also assessed as an independent measure of the potential motoric effects of this NO donor.

RESULTS

SNP (0.3 and 1 mg/kg) reversed ketamine (3 mg/kg)-induced short-term recognition memory deficits. SNP (1 mg/kg) counteracted the ketamine (8 mg/kg)-induced social isolation in the social interaction test. The anxiolytic-like effects in the light/dark test of SNP (1 mg/kg) cannot be attributed to changes in locomotor activity.

CONCLUSIONS

Our findings illustrate a functional interaction between the nitrergic and glutamatergic system that may be of relevance for schizophrenia-like behavioural deficits. The data also suggest a role of NO in anxiety.

Cannabinoid type-1 receptor signaling in central serotonergic neurons regulates anxiety-like behavior and sociability

The endocannabinoid (eCB) system possesses neuromodulatory functions by influencing the release of various neurotransmitters, including γ-aminobutyric acid (GABA) and glutamate. A functional interaction between eCBs and the serotonergic system has already been suggested. Previously, we showed that cannabinoid type-1 (CB1) receptor mRNA and protein are localized in serotonergic neurons of the raphe nuclei, implying that the eCB system can modulate serotonergic functions. In order to substantiate the physiological role of the CB1 receptor in serotonergic neurons of the raphe nuclei, we generated serotonergic 5-hydroxytryptamine (5-HT) neuron-specific CB 1 receptor-deficient mice, using the Cre/loxP system with a tamoxifen-inducible Cre recombinase under the control of the regulatory sequences of the tryptophan hydroxylase 2 gene (TPH2-CreER (T2)), thus, restricting the recombination to 5-HT neurons of the central nervous system (CNS). Applying several different behavioral paradigms, we revealed that mice lacking the CB1 receptor in serotonergic neurons are more anxious and less sociable than control littermates. Thus, we were able to show that functional CB1 receptor signaling in central serotonergic neurons modulates distinct behaviors in mice.

2-(4-substituted piperazin-1-yl)-1,8-naphthyridine-3-carboxylic acids: Novel 5-HT3 receptor antagonists with anxiolytic-like activity in rodent behavioral models

The aim of this study was to investigate the anxiolytic potential of a series of novel carboxylic acid based 1,8 naphthyridines as 5-HT3 receptor antagonists. The pA2 values of all the compounds were determined against agonist 2-methyl-5-hydroxytryptamine in longitudinal muscle myenteric plexus preparations from guinea pig ileum. Compounds with higher pA2 values, particularly those greater than ondansetron, a standard 5-HT3 receptor antagonist, and optimal log P values were screened in mice by using behavioral tests such as a light–dark (L/D) aversion test, elevated plus maze (EPM) test, and an open field test (OFT). In the L/D test, compounds 7a, 7b, 7d, 7e, and 7i (2 mg/kg body mass, intraperitoneal) significantly (P < 0.05) increased the latency time to leave the light compartment, total time spent in the light compartment, and the number of transitions between the light and dark compartments. Compounds 7a, 7d, 7f, 7h, and 7i (2 mg/kg, i.p.) significantly (P < 0.05) increased the time spent in the open arms and the number of entries into the open arms in the EPM test. In addition, compounds 7a, 7d, 7e, 7f, and 7h (2 mg/kg, i.p.) significantly (P < 0.05) increased the ambulation scores and the frequency of rearing in the OFT.

The metabotropic glutamate 2/3 receptor agonist LY379268 induces anxiety-like behavior at the highest dose tested in two rat models of anxiety

The activation of Group II metabotropic glutamate 2/3 (mGlu2/3) receptors reduces the excessive glutamate release that is hypothesized to be associated with neurodegenerative and psychiatric disorders. LY379268 is a highly potent mGlu2/3 receptor agonist that has shown efficacy in several animal models of stroke, epilepsy, drug abuse, schizophrenia, and pain. The present study investigated the effects of LY379268 on anxiety-like behavior in rats assessed in the light/dark and open field tests. The effects of LY379268 on motility in a locomotor activity chamber were also investigated in rats. Administration of the two lower doses of LY379268 used (0.3 and 1mg/kg) did not influence rats' performance either in the light/dark or in the open field test. Importantly, the administration of a higher LY379268 dose (3mg/kg) induced decrease in the number of transitions between the light and dark chambers and time spent in the light chamber compared to the vehicle-treated animals in the light/dark test. In the open field test, rats that received 3mg/kg LY379268 made fewer entries and spent less time in the central zone of the apparatus, exhibited a decrease of rearing episodes, but displayed higher grooming activity compared to controls. Nevertheless, the 3mg/kg dose did not alter locomotor activity compared with vehicle-treated rats in a motility test. The present results indicate that the highest LY379268 dose used in this study induced an anxiety-like effect in the light/dark and open field tests that cannot be attributed to changes in locomotor activity, while lower doses had no effect.

A comparison of dehydroepiandrosterone and 7-keto dehydroepiandrosterone with other drugs that modulate ethanol intake in rats responding under a multiple schedule

Dehydroepiandrosterone (DHEA), 7-keto DHEA, and several comparison drugs (ethanol, chlordiazepoxide, rauwolscine, and RO15-4513) were administered to male rats responding under a multiple schedule of food and ethanol presentation to determine their selectivity for decreasing ethanol-maintained responding. DHEA and 7-keto DHEA significantly decreased both ethanol-maintained and food-maintained responding, compared with the control, while also decreasing the blood ethanol concentration (BEC). Acute ethanol administration also decreased responding for both food and ethanol; however, ethanol-maintained responding was more potently decreased than food-maintained responding. BEC remained relatively stable after increasing ethanol doses. Among the other drugs tested, RO15-4513 was the most selective for decreasing ethanol-maintained responding compared with food-maintained responding, and it decreased BECs as ethanol-maintained responding decreased. The largest dose of rauwolscine significantly decreased responding for food, whereas it did not affect ethanol-maintained responding compared with the control. Low to intermediate doses of rauwolscine produced small, nonsignificant increases in ethanol-maintained responding and BECs. Chlordiazepoxide produced significant decreases in food-maintained responding and the dose of ethanol presented, but only at the highest dose tested. Although DHEA and 7-keto DHEA did not decrease ethanol-maintained responding as selectively as ethanol or RO15-4513 under the multiple schedule, these neurosteroids may be valuable pharmacological tools in the development of new treatments for alcohol abuse and dependence.

Anxiolytic activity of methanol leaf extract of Achyranthes aspera Linn in mice using experimental models of anxiety

OBJECTIVE

To study the anxiolytic activity of methanol extract of Achyranthes aspera Linn (Amaranthaceae).

MATERIALS AND METHODS

Male Swiss albino mice were used. Methanolic extract of Achyranthes aspera (MEAA) was administered in the doses of 100, 300 and 600 mg/kg p.o. Hole board (HB), open field (OF), elevated plus maze (EPM) and light/dark exploration (LDE) tests were used for determination of anxiolytic activity.

RESULTS

The methanolic extract of Achyranthes aspera significantly increased the number and duration of head poking in HB test. The extract also significantly increased the time spent and the number of entries in open arm in EPM. In LDE test, the extract produced significant increase in time spent and number of crossings and decreased the duration of immobility in light box. In OFT, the extract showed significant increase in number of rearing, assisted rearing and the squares crossed.

CONCLUSION

In the present study, MEAA exhibited anxiolytic activity which might be attributed to its phyto-constituents viz. alkaloid, steroid and triterpenes. Since Achyranthes aspera is ubiquitous and abundantly grown, it could be a fairly economical therapeutic agent for management of anxiety disorders.

Involvement of 5-HT1A in the anxiolytic-like effect of dichloromethane fraction of Pimenta pseudocaryophyllus

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal applications of Pimenta pseudocaryophyllus infusion as a diuretic and aphrodisiac agent as well as tranquilizer in the form of tea for the treatment of emotional tension in Brazilian folk medicine has been in practice since time immemorial. Despite its popular therapeutic acceptance and claims, there are scanty scientific reports to corroborate its central biological activities.

AIM

To characterize anxiolytic-like effect of the dichloromethane fraction (DF) obtained from ethanolic leaf extract of the Pimenta pseudocaryophyllus and identify mechanisms of action involved while seeking to support its popular use as a soothing agent.

MATERIAL AND METHODS

Mice (25-35 g) were treated orally with DF obtained from ethanolic leaf extract of Pimenta pseudocaryophyllus and were submitted to light-dark box (LDB) and elevated plus maze (EPM) tests. Different groups of mice were treated with flumazenil and NAN-190 to identify mechanisms of action involved in the anxiolytic-like effect of DF.

RESULTS

Treatment with DF increased number of transitions and time spent in the light compartment of the LDB while the time spent and numbers of entries in the open arm of the LCE were significantly increased. Pre-treatment of the animal with flumazenil (2 mg/kg, i.p.--competitive antagonist of benzodiazepine site of GABA(A) receptor) did not block this effect, thereby excluding participation of benzodiazepine site of the GABA(A) receptor. However, anxiolytic-like effect of DF was reversed by pre-treatment with NAN-190 (0.5 mg/kg, i.p.--an antagonist of the 5-HT(1A) receptor) thereby suggesting involvement of 5-HT(1A) receptor. The thin layer chromatography and high-performance liquid chromatography analysis indicated the predominance of (E)-methyl isoeugenol and oleanolic acid in DF.

CONCLUSION

These results support the popular use of Pimenta pseudocaryophyllus as a calming agent and suggest the involvement of 5-HT(1A) receptor.

Isolation of anxiolytic principle from ethanolic root extract of Cardiospermum halicacabum

Cardiospermum halicacabum roots have been used traditionally for the treatment of epilepsy and anxiety disorders. The purpose of this study was to characterize the putative phytoconstituents present in the ethanolic root extract having anxiolytic activity using an elevated plus-maze (EPM) and light dark transition model. Control mice were orally treated with an equal volume of vehicle (4% gum acacia), and positive control mice were treated with diazepam (1mg/kg). In the EPM test, out of pool of 19 master fractions (MF) only MF-14, 16 and 17 significantly (30mg/kg, p<0.05, p<0.01 and p<0.001) increased the number of entries in the open arm. MF-14, 16 and 17 (10, 20 and 30mg/kg) had also increased the time spent by mice in illuminated part of the box significantly (p<0.05, p<0.01 and p<0.001), as compared to control. However, significant changes (p<0.05, p<0.01 and p<0.001) were recorded in other parameters, e.g., rearing, time spent in the closed arm and dark zone in both the models. These results suggested that C. halicacabum root is an effective anxiolytic agent. The phytoconstituent responsible for the observed central effects was isolated from MF-14 and identified as well-known compound, Cardiospermin, a cyanogenic glucoside.

Decreased GABAA receptors and benzodiazepine binding sites in the anterior cingulate cortex in autism

The anterior cingulate cortex (ACC; BA 24) via its extensive limbic and high order association cortical connectivity to prefrontal cortex is a key part of an important circuitry participating in executive function, affect, and socio-emotional behavior. Multiple lines of evidence, including genetic and imaging studies, suggest that the ACC and gamma-amino-butyric acid (GABA) system may be affected in autism. The benzodiazepine binding site on the GABA(A) receptor complex is an important target for pharmacotherapy and has important clinical implications. The present multiple-concentration ligand-binding study utilized (3)H-muscimol and (3)H-flunitrazepam to determine the number (B(max)), binding affinity (K(d)), and distribution of GABA(A) receptors and benzodiazepine binding sites, respectively, in the ACC in adult autistic and control cases. Compared to controls, the autistic group had significant decreases in the mean density of GABA(A) receptors in the supragranular (46.8%) and infragranular (20.2%) layers of the ACC and in the density of benzodiazepine binding sites in the supragranular (28.9%) and infragranular (16.4%) lamina [corrected]. These findings suggest that in the autistic group this downregulation of both benzodiazepine sites and GABA(A) receptors in the ACC may be the result of increased GABA innervation and/or release disturbing the delicate excitation/inhibition balance of principal neurons as well as their output to key limbic cortical targets. Such disturbances likely underlie the core alterations in socio-emotional behaviors in autism.

Pharmacological alterations of anxious behaviour in mice depending on both strain and the behavioural situation

A previous study comparing non-emotive mice from the strain C57BL/6/ByJ with ABP/Le mice showed ABP/Le to be more anxious in an open-field situation. In the present study, several compounds affecting anxiety were assayed on ABP/Le and C57BL/6/ByJ mice using three behavioural models of anxiety: the elevated plus-maze, the light-dark discrimination test and the free exploratory paradigm. The compounds used were the full benzodiazepine receptor agonist, chlordiazepoxide, and the antagonist, flumazenil, the GABA(A) antagonist, bicuculline, the full 5-HT(1A) agonist 8-OH-DPAT, and the mixed 5-HT(1A)/5-HT(1B) agonist, RU 24969. Results showed the effect of the compounds to be dependent on both the strain and the behavioural task. Several compounds found to be anxiolytic in ABP/Le mice had an anxiogenic effect on C57BL/6/ByJ mice. More behavioural changes were observed for ABP/Le in the elevated plus-maze, but the clearest findings for C57BL/6/ByJ mice were observed in the light-dark discrimination apparatus. These data demonstrate that anxious behaviour is a complex phenomenon which cannot be described by a single behavioural task nor by the action of a single compound.

Glutaminase-deficient mice display hippocampal hypoactivity, insensitivity to pro-psychotic drugs and potentiated latent inhibition: relevance to schizophrenia

Dysregulated glutamatergic neurotransmission has been strongly implicated in the pathophysiology of schizophrenia (SCZ). Recently, presynaptic modulation of glutamate transmission has been shown to have therapeutic promise. We asked whether genetic knockdown of glutaminase (gene GLS1) to reduce glutamatergic transmission presynaptically by slowing the recycling of glutamine to glutamate, would produce a phenotype relevant to SCZ and its treatment. GLS1 heterozygous (GLS1 het) mice showed about a 50% global reduction in glutaminase activity, and a modest reduction in glutamate levels in brain regions relevant to SCZ pathophysiology, but displayed neither general behavioral abnormalities nor SCZ-associated phenotypes. Functional imaging, measuring regional cerebral blood volume, showed hippocampal hypometabolism mainly in the CA1 subregion and subiculum, the inverse of recent clinical imaging findings in prodromal and SCZ patients. GLS1 het mice were less sensitive to the behavioral stimulating effects of amphetamine, showed a reduction in amphetamine-induced striatal dopamine release and in ketamine-induced frontal cortical activation, suggesting that GLS1 het mice are resistant to the effects of these pro-psychotic challenges. Moreover, GLS1 het mice showed clozapine-like potentiation of latent inhibition, suggesting that reduction in glutaminase has antipsychotic-like properties. These observations provide further support for the pivotal role of altered glutamatergic synaptic transmission in the pathophysiology of SCZ, and suggest that presynaptic modulation of the glutamine-glutamate pathway through glutaminase inhibition may provide a new direction for the pharmacotherapy of SCZ.

Decreased immobility in swimming test by homologous interferon-alpha in mice accompanied with increased cerebral tryptophan level and serotonin turnover

Animal models are used to decipher the pathophysiology of IFN-alpha-induced psychiatric complications in humans. However, the behavioral effects of IFN-alpha in rodents remain highly controversial. In contrast to homologous IFN-alpha, our recent study revealed that human IFN-alpha, which was used in many previous investigations, had no biological activity in mice. To evaluate the behavioral effects of homologous IFN-alpha in mice, adult C57BL/6J mice were treated with carrier-free murine IFN-alpha and tested on a number of behavioral paradigms. Surprisingly, contrary to previous reports, IFN-alpha treatment decreased the time spent immobile in the forced-swimming test after a single intraperitoneal injection at 2 x 10(6)IU/kg, whereas general locomotor activity was not altered. The elevated plus-maze (EPM) test showed a trend toward an increased anxiety profile in IFN-alpha-treated mice. The tail-suspension and light dark exploration test revealed no difference between IFN-alpha-treated and control animals. Interestingly, neurochemical analysis revealed significantly increased concentrations of tryptophan and 5-hydroxyindoleacetic acid (5-HIAA)/serotonin (5-HT) ratios following IFN-alpha treatment in selected brain regions. Thus, systemic murine IFN-alpha treatment increases swimming time in mice. Increased cerebral serotonin turnover as well as increased tryptophan concentrations, induced by IFN-alpha, implicates serotonergic neurotransmission in behavioral dysfunction caused by this innate immune mediator.

Synaptic imbalance, stereotypies, and impaired social interactions in mice with altered neuroligin 2 expression

The level of excitation in the brain is kept under control through inhibitory signals mainly exerted by GABA neurons. However, the molecular machinery that regulates the balance between excitation and inhibition (E/I) remains unclear. Candidate molecules implicated in this process are neuroligin (NL) adhesion molecules, which are differentially enriched at either excitatory or inhibitory contacts. In this study, we use transgenic mouse models expressing NL1 or NL2 to examine whether enhanced expression of specific NLs results in synaptic imbalance and altered neuronal excitability and animal behavior. Our analysis reveals several abnormalities selectively manifested in transgenic mice with enhanced expression of NL2 but not NL1. A small change in NL2 expression results in enlarged synaptic contact size and vesicle reserve pool in frontal cortex synapses and an overall reduction in the E/I ratio. The frequency of miniature inhibitory synaptic currents was also found to be increased in the frontal cortex of transgenic NL2 mice. These animals also manifested stereotyped jumping behavior, anxiety, impaired social interactions, and enhanced incidence of spike-wave discharges, as depicted by EEG analysis in freely moving animals. These findings may provide the neural basis for E/I imbalance and altered behavior associated with neurodevelopmental disorders.

Long-term consequences of soman poisoning in mice: part 2. Emotional behavior

The organophosphorus compound soman produces long-lasting epileptic seizure activity which is associated to brain damage, more particularly in the hippocampus and the amygdala. The companion paper (see part 1 in the same journal issue) describes the neuropathology in the amygdala of soman-poisoned mice. The present paper examines the long-term effects of soman poisoning on emotional reactivity in mice, 30 or 90 days after intoxication using behavioral tasks involving amygdala function. The emotional behavior was estimated in animal tests of unconditioned fear (light/dark boxes, elevated plus-maze) and conditioned fear (auditory and contextual response). In the light/dark boxes and elevated plus-maze, mice intoxicated with soman (110 microg/kg, 1.2 LD(50)) showed an anxiety-like behavior profile at post-poisoning days 30 and 90. In conditioned fear, results showed that both auditory and contextual conditioned responses are increased on post-soman day 30 but no longer on post-soman day 90, evidencing behavioral recovery overtime. This latter behavioral result is in accordance with the delayed neuronal regeneration patterns described in the companion paper (part 1).

Protracted 'pro-addictive' phenotype produced in mice by pre-adolescent phenylpropanolamine

For decades, the sympathomimetic phenylpropanolamine (PPA; +/- -norepinephrine) was an active ingredient found in popular children's over-the-counter (OTC) cold, cough, and allergy medications. To examine the possibility that pre-adolescent PPA exposure may induce neuroadaptations that influence behavioral and neurochemical responding to cocaine, C57BL/6J mice were pretreated with PPA (0-40 mg/kg) during postnatal days 21-31. The behavioral and neurochemical responses to acute and repeated cocaine (4 x 15 mg/kg) were then assessed in adulthood when the mice were 10 weeks of age. Whereas pre-adolescent PPA exposure did not influence the acute locomotor response to 15 mg/kg cocaine, PPA pre-exposure dose-dependently enhanced the expression of cocaine-induced place conditioning, reduced the expression of locomotor sensitization, but did not influence cocaine-induced stereotypy. Pre-adolescent PPA exposure completely prevented the capacity of cocaine to elevate extracellular levels of catecholamines in the nucleus accumbens, but facilitated the development of cocaine-induced glutamate sensitization. Neither acute nor repeated cocaine altered extracellular GABA levels in the accumbens of control mice; however, 15 mg/kg cocaine lowered GABA levels by approximately 40% in PPA pretreated mice and this effect showed tolerance with repeated cocaine administration. These data provide the first evidence that early exposure to an OTC compound produces protracted effects upon cocaine-induced changes in nucleus accumbens neurotransmission that may contribute to a 'pro-addictive' phenotype in adulthood.

Anxiety in mice: a principal component analysis study

Two principal component analyses of anxiety were undertaken investigating two strains of mice (ABP/Le and C57BL/6ByJ) in two different experiments, both classical tests for assessing anxiety in rodents. The elevated plus-maze and staircase were used for the first experiment, and a free exploratory paradigm and light-dark discrimination were used for the second. The components in the analyses produced definitions of four fundamental behavior patterns: novelty-induced anxiety, general activity, exploratory behavior, and decision making. We also noted that the anxious phenotype was determined by both strain and experimental procedure. The relationship between behavior patterns and the use of specific tests plus links with the genetic background are discussed.

Efficacy of the MCHR1 Antagonist N-[3-(1-{[4-(3,4-Difluorophenoxy)phenyl]methyl}(4-piperidyl))-4-methylphenyl]-2-methylpropanamide (SNAP 94847) in Mouse Models of Anxiety and Depression following Acute and Chronic Administration Is Independent of Hippocampal Neurogenesis

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that plays a role in the modulation of food intake and mood. In rodents, the actions of MCH are mediated via the MCHR1 receptor. The goal of this study was to investigate the effects of acute (1 h) and chronic (28 days) p.o. dosing of a novel MCHR1 antagonist, N-[3-(1-{[4-(3,4-difluorophenoxy)-phenyl]methyl}(4-piperidyl))-4-methylphenyl]-2-methylpropanamide (SNAP 94847), in three mouse models predictive of antidepressant/anxiolytic-like activity: novelty suppressed feeding (NSF) in 129S6/SvEvTac mice and light/dark paradigm (L/D) and forced swim test (FST) in BALB/cJ mice. A significant increase in the time spent in the light compartment of the L/D box was observed in response to acute and chronic treatment with SNAP 94847. An anxiolytic/antidepressant-like effect was found in the NSF test after acute and chronic treatment, whereas no effect was observed in the FST. Because neurogenesis in the dentate gyrus has been shown to be a requirement for the effects of antidepressants in the NSF test, we investigated whether neurogenesis was required for the effect of SNAP 94847. We showed that chronic treatment with SNAP 94847 stimulated proliferation of progenitors in the dentate gyrus. The efficacy of SNAP 94847 in the NSF test, however, was unaltered in mice in which neurogenesis was suppressed by X-irradiation. These results indicate that SNAP 94847 has a unique anxiolytic-like profile after both acute and chronic administration and that its mechanism of action is distinct from that of selective serotonin reuptake inhibitors and tricyclic antidepressants.

Anticonvulsant and anxiolytic activity of FrPbAII, a novel GABA uptake inhibitor isolated from the venom of the social spider Parawixia bistriata (Araneidae: Araneae)

This study was aimed at determining the effects of FrPbAII (174 Da), a novel isolated component from Parawixia bistriata spider venom, in the CNS of Wistar rats. Considering that FrPbAII inhibits the high affinity GABAergic uptake in a dose-dependent manner, its anxiolytic and anticonvulsant effects were analyzed in well-established animal models. Injection of FrPbAII in the rat hippocampus induced a marked anxiolytic effect, increasing the occupancy in the open arms of the elevated plus maze (EC(50)=0.09 microg/microl) and increasing the time spent in the lit area of the light-dark apparatus (EC(50)=0.03 microg/microl). Anxiolytic effects were also observed considering the number of entries in the open arms of the EPM and in the lit compartment of the light-dark box. Interestingly, when microinjected bilaterally in the SNPr of freely moving rats, FrPbAII (0.6 microg/microl) effectively prevented seizures induced by the unilateral GABAergic blockade of Area tempestas (bicuculline, 0.75 microg/microl). This anticonvulsant effect was similar to that evoked by muscimol (0.1 microg/microl) and baclofen (0.6 microg/microl), but differed from that of the specific GAT1 inhibitor, nipecotic acid (0.7 microg/microl). This difference could be accounted either for the parallel action of FrPbAII over glycinergic transporters or to an inspecific activity on GABAergic transporters. Data from the present investigation might be pointing to a novel compound with interesting and yet unexplored pharmacological potential.

Preliminary study on immunological and behavioural effects of Thymus broussonetii Boiss., an endemic species in Morocco

In the present work, we had tried to evaluate the immunotropic and behavioural effects of Thymus broussonetii Boiss. So, we tested the neurostimulant effects of four extracts. This preliminary study allowed to identify both the immunostimulant and the neurotropic antistress effects of the studied extracts. Among the four extracts, only the aqueous and ethyl acetate ones showed an apparent effect on the tested biological activities, whereas the butanolic extract and the essential oil did not show any interesting effect (data not shown). These results showed that the aqueous and ethyl extracts of this endemic species are of interest for two reasons: stimulation of the immunizing system and protection against the stress by a neurotropic activity. Thyme extracts increased in vivo the number of leucocyte categories studied including polynuclears, total lymphocytes, TCD4+, TCD8+ and NK cells. These data suggest that the intraperitoneal administration of Thymus broussonetii extract has a potent direct effect on leucocytes in vivo. The elevation of leucocyte and thrombocyte counts produced by thyme in the peripheral blood was already reported in the literature. These results could be of practical importance in the field of phytotherapy in the treatment of some cases of human immunodeficiency such as cancer, leukaemia and AIDS.

Increased fear response to contextual cues in mice lacking the 5-HT1A receptor

Serotonin 1A receptor knockout (5-HT1AR KO) mice exhibit increased behavioral inhibition in conflict tests. To gain further insight into their anxiety-related phenotype, we subjected these mice to additional behavioral tests. First, we considered whether behavioral inhibition in these knockout mice is a consequence of reduced exploratory motivation. The knockout mice engage in normal exploration during a light-dark test and normal exploration of a novel object in a familiar environment, suggesting that the anxiety-related phenotype is not due to reduced exploratory drive. Second, we tested whether these mice exhibit increased behavioral inhibition in response to any aversive cues, or whether this response depends on cue modality. Knockout mice respond normally to discrete aversive cues in the Vogel lick-suppression test, arguing that their phenotype is restricted to conflict tests based on complex or spatial aversive cues. Third, to probe the processing of spatial aversive cues, we assessed fear conditioning to contextual cues. After contextual fear conditioning, knockout and wild-type (WT) mice express freezing responses when exposed to the training environment. However, when placed in an ambiguous environment containing both conditioned and novel cues, the freezing response of knockout mice does not significantly decrease as it does in WT mice, suggesting that the knockout fear response is biased toward threatening cues. We hypothesize that this inappropriate generalization of fearful behavior to a context containing both fearful and neutral stimuli, a phenomenon that occurs in a subset of human anxiety disorders such as panic disorder and post-traumatic stress disorder, underlies the anxiety phenotype of 5-HT1AR KO mice.

Abnormal benzodiazepine receptor function in the depressive-like behavior of diabetic mice

We previously reported that streptozotocin (STZ)-induced diabetic mice exhibited depressive-like behavior in the tail suspension test. In this study, we examined the involvement of benzodiazepine receptor functions in this diabetes-induced depressive-like behavior in mice. STZ-induced diabetes significantly increased the duration of immobility without affecting spontaneous locomotor activity. This increase was dose-dependently and significantly suppressed by a benzodiazepine receptor antagonist, flumazenil (0.1-1 mg/kg, i.v.). However, flumazenil (0.1-1 mg/kg, i.v.) did not affect the duration of immobility in non-diabetic mice. Furthermore, flumazenil (1 mg/kg, i.v.) had no significant effect on spontaneous locomotor activity in either non-diabetic or diabetic mice. The benzodiazepine receptor inverse agonist methyl beta-carboline-3-carboxylate (beta-CCM; 0.03-0.3 mg/kg, i.v.) dose-dependently and significantly increased the duration of immobility in non-diabetic mice, but not in diabetic mice. beta-CCM (0.3 mg/kg, i.v.) significantly suppressed spontaneous locomotor activity in non-diabetic mice, but not in diabetic mice. These results indicate that diabetic mice may have enhanced negative allosteric modulation by benzodiazepine receptor ligands, such as diazepam binding inhibitors, under stressful conditions, but not free-moving conditions, and this abnormal function of benzodiazepine receptors may cause, at least in part, the expression of depressive-like behavior in diabetic mice.

Genetic variation in heroin-induced changes in behaviour: effects of B6 strain dose on conditioned reward and locomotor sensitization in 129-B6 hybrid mice

Substantial interindividual variability exists in the propensity to develop opiate addiction. Genetic variation in opiate reward may contribute to this variability. A large body of evidence indicates genetic variation in mice for several effects of opiate drugs. The present study examined heroin-induced place conditioning and locomotor sensitization in the two strains of mice employed most frequently in the generation of transgenic animals, C57BL/6J (B6) and 129X1/sVJ (129), as well as in groups of B6-129 hybrid mice, differing in their amount of B6 genetic background. Four pairings of 100 microg/kg of heroin elicited robust place conditioning and locomotor sensitization in B6 controls and in N(10) congenic B6-129 hybrid mice. In comparison, the identical treatment produced no locomotor sensitization and induced place aversion in 129 controls. No heroin-induced changes in the behaviour of N(3) congenic B6-129 hybrid mice or F5-8 non-congenic B6-129 hybrid mice were observed. The expression of place conditioning was not facilitated in any group by the administration of a heroin-priming injection prior to testing. These data indicate that genetic variation exists in mice for the rewarding and locomotor-sensitizing effects of heroin and that the capacity of heroin to induce conditioned reward and locomotor sensitization can be modulated in a B6 strain dose-dependent manner in B6-129 hybrid mice. Thus, strain differences in heroin responsiveness should be considered when examining transgenic lines on B6-129 backgrounds for opiate-induced changes in behaviour that may be relevant for addiction.

The effects of angelica essential oil in three murine tests of anxiety

The effects of angelica essential oil in three assays predictive of anxiolytic activity in male mice were studied, with diazepam as a positive anxiolytic control. In the elevated plus-maze test, compared to the positive control diazepam, angelica essential oil (30.0 mg/kg, PO) had a modest anxiolytic-like effect (increased the percentage of open-arm time and reduced the percent protected head dips). In the light/dark test, angelica essential oil (30.0 mg/kg) prolonged the time spent in the light area without altering the locomotor activity of the animals. In the stress-induced hyperthermia test, 60 and 70 min after drug administration, rectal temperature was measured twice, angelica essential oil at the dose of 30.0 mg/kg inhibited stress-induced hyperthermia. Thus, these findings indicate that angelica essential oil, as does diazepam, exhibits an anxiolytic-like effect. Further studies will be required to assess the generality of the present findings to other species and behavioural paradigms.

Bidirectional effects of benzodiazepine binding site ligands in the elevated plus-maze: differential antagonism by flumazenil and beta-CCt

Recent research using genetically modified mice has pointed to the specific contribution of individual receptor subtypes to the various effects of benzodiazepines. The aim of this study was to examine the relative significance of alpha(1)-containing GABA(A) receptors in the effects of modulators at the benzodiazepine site in the elevated plus-maze (EPM) under dim red light in rats. We tested the effects of the non-selective antagonist flumazenil (0-20.0 mg/kg), the preferential alpha(1)-subunit selective antagonist beta-carboline-3-carboxylate-t-butyl ester (beta-CCt, 0-30.0 mg/kg), the non-selective agonist midazolam (0-2.0 mg/kg), the preferential alpha(1)-subunit selective agonist zolpidem (0-2.0 mg/kg) and the non-selective inverse agonist methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM, 0-2.0 mg/kg). The influence of flumazenil (10.0 mg/kg) and beta-CCt (30.0 mg/kg) on the effects of both kinds of agonists were also examined. The standard spatio-temporal parameters reflecting anxiety (percentage of open arm entries and time) and locomotion (closed and total arm entries) were analyzed. beta-CCt did not affect behavior, while flumazenil at the highest dose (20.0 mg/kg) decreased indices of open arm activity and total arm entries. Midazolam at the dose of 1.0 mg/kg significantly increased the percentage of open arm time, whereas at 2.0 mg/kg both anxiety-related parameters were increased. In contrast to the open arm entries, the open arm time was independent of the decreased closed arm entries, observed at 2.0 mg/kg. Flumazenil abolished these effects, whereas beta-CCt partially potentiated the anxiolytic actions of midazolam. Zolpidem significantly increased both open-arm indices at 1.0 mg/kg, but the effect was dependent on the decreased closed arm entries. The selectivity of the anxiolytic-like effects of zolpidem was further checked under brighter white illumination. In these settings, the influence on anxiety-related, but not activity-related parameters, was absent. All of the activity-related effects of midazolam and zolpidem were mainly counteracted by both antagonists. DMCM produced significant anxiogenic effects at 1.0 mg/kg (open arm time) and 2.0 mg/kg (both parameters). beta-CCt (30.0 mg/kg) and flumazenil at higher dose (20.0 mg/kg) antagonized the effects of DMCM. The results indicate the anxiolytic effects of a non-selective benzodiazepine site agonist involve a predominant role of subunits other than alpha(1), whereas the behavioral indices of the anxiolytic-like properties of an alpha(1)-selective ligand, if observed, depend on the experimental settings and the changes in locomotor activity, and hence were behaviorally non-specific. The present results generally correspond well to the behavioral findings with the genetically modified mice. On the other hand, the relative significance of the alpha(1)-subunit in the anxiogenic effects of DMCM could not be clearly deduced.