Involvement of diazepam-insensitive benzodiazepine receptors in the suppression of DOI-induced head-twitch responses in diabetic mice

Rationale We previously reported that the head-twitch responses induced by the 5-HT₂ receptor agonist (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) (DOI-HTRs) were decreased in streptozotocin-induced diabetic mice.Objectives We examined the involvement of γ-aminobutyric acid (GABA)/benzodiazepine system on the suppression of DOI-HTRs in diabetic mice.Results The benzodiazepine receptor antagonist flumazenil (0.1–1 mg/kg, i.v.) dose-dependently and significantly increased DOI-HTRs in diabetic mice to the same levels as in nondiabetic mice. However, flumazenil (0.1–1 mg/kg, i.v.) did not affect DOI-HTRs in nondiabetic mice. The benzodiazepine receptor agonist diazepam (0.1–1 mg/kg, i.p.) had no effect on DOI-HTRs in either nondiabetic or diabetic mice. The GABA_A receptor antagonist bicuculline (0.1–1 mg/kg, i.p.) and the benzodiazepine receptor partial inverse agonist Ro 15-4513 (0.1–1 mg/kg, i.v.) dose-dependently and significantly suppressed DOI-HTRs in nondiabetic mice to the same levels as in diabetic mice. Ro 15-4513-induced reduction of DOI-HTRs in nondiabetic mice was completely antagonized by flumazenil (1 mg/kg, i.v.), but not diazepam (0.3 mg/kg, i.p.).Conclusions We suggest that the abnormal diazepam-insensitive benzodiazepine receptor function partly underlies the suppression of DOI-HTRs in diabetic mice.     

Protective effect of St. John's wort (Hypericum perforatum) extract on 72-hour sleep deprivation-induced anxiety-like behavior and oxidative damage in mice

Sleep disruption or poor quality of sleep is a common problem associated with depression. Antidepressant drugs have been reported to improve the quality of sleep and behavior. The present study was undertaken to explore the therapeutic potential of Hypericum perforatum (St. John's wort) on behavioral alterations and oxidative damage induced by sleep deprivation in mice. Male laca mice (n = 6 - 10 in each group) were sleep deprived for 72 hours using the grid suspended over water method. Standardized Hypericum perforatum extract and imipramine were administered for five days, starting two days before sleep deprivation. Alterations in body weight, motor activity, anxiety like behavior (mirror chamber, plus maze, zero maze) and oxidative stress parameters (reduced glutathione, catalase, lipid peroxidation and nitrite levels) were observed after drug treatment in sleep-deprived animals. 72-hour sleep deprivation significantly altered body weight, locomotor activity and produced anxiety-like behavior and oxidative damage (depleted reduced glutathione, catalase activity and increased lipid peroxidation and nitrite activity) as compared to the na?ve (placed on sawdust) animals (P < 0.05). Treatment with either St. John's wort (200 and 400 mg/kg, P. O.) or with imipramine (10 mg/kg, I. P.) significantly improved body weight, locomotor activity, antianxiety and antioxidant effect as compared to the control group (sleep deprived) (P < 0.05). Co-administration of John's wort (200 mg/kg, P. O.) with imipramine (10 mg/kg, I. P.) further improved body weight, locomotor activity, antianxiety effect as well as reduced oxidative damage in sleep-deprived animal as compared to their effect per se (P < 0.05). The present study suggests that there is therapeutic potential of St. John's wort in the management of sleep deprivation-induced anxiety-like behavior and oxidative damage.     

The involvement of magnoflorine in the sedative and anxiolytic effects of Sinomeni Caulis et Rhizoma in mice

The present study seeks to evaluate the sedative and anxiolytic effects of the 70 % ethanol extract of Sinomeni Caulis et Rhizoma (SR). The extract was orally administered to mice at dosages of 25, 50, 100, 200 or 400 mg/kg. The mice were then subjected to an array of behavioral tests to assess the sedative (open-field, rota-rod, and thiopental sodium-induced sleeping test) and anxiolytic (elevated plus maze test) effects of the substance. SR (100, 200 mg/kg) significantly reduced locomotor activity, decreased rota-rod performance, and potentiated thiopental sodium-induced sleeping in mice, all indicative of its sedative effects. SR (50, 100 mg/kg) also produced anxiolytic effects, as shown by an increase in entries and staying time on the open arm of the plus maze. SR’s sedative and anxiolytic effects were comparable to that of the benzodiazepine, diazepam. Moreover, to identify SR’s probable mechanism of action, intracellular Cl^? ion influx was observed in cultured human neuroblastoma cells. SR dose-dependently increased Cl^? influx, which was blocked by co-administration of the GABA_A receptor competitive antagonist, bicuculline. Among the major constituents of SR, only magnoflorine showed a similar increment in Cl^? influx, which was also blocked by bicuculline. Altogether, the present results suggest that SR has sedative and anxiolytic effects, probably mediated by magnoflorine through a GABAergic mechanism of action.     

Extracts of kava (<Emphasis Type="Italic">Piper methysticum</Emphasis>) induce acute anxiolytic-like behavioral changes in mice

Rationale Kava has been used for centuries by Pacific Islanders for its tranquilizing and sedative effects. Recent clinical trials suggest that kava has therapeutic value for the treatment of anxiety. Demonstration of kava's anxiolytic effects in animals under controlled conditions would provide additional support for its clinical potential as an anxiolytic and would facilitate investigation of its mechanism(s) of action.Objectives This study systematically characterized the acute dosage-dependent anxiolytic and sedative effects of kava extract in well established quantitative murine behavioral assays and compared kava- and diazepam-induced behavioral changes.Methods Various doses of an ethanolic extract of kava root or diazepam were administered intraperitoneally to BALB/cByJ inbred mice. Behavioral changes were measured in the mirrored chamber avoidance assay and elevated plus-maze assay. Reduced latency to enter and increased time spent in a normally avoided environment operationally defined anxiolysis. Sedation was defined by a significant decrease in locomotor activity in a circular arena.Results Kava extract produced statistically significant dose-dependent anxiolytic-like behavioral changes in both assays of anxiolysis. ED₅₀ values for kava-induced increases in time spent inside the mirrored chamber and on the open arms of the plus maze were 125 mg/kg and 88 mg/kg, respectively. Kava extract also caused a profound decrease in locomotor activity (ED₅₀ of 172 mg/kg). Flumazenil, a competitive benzodiazepine receptor antagonist, blocked both the anxiolytic and sedative effects of diazepam, but had no effect on kava's behavioral actions.Conclusions Kava extracts produce significant murine anxiolytic-like behavioral changes and sedation that are not mediated through the benzodiazepine binding site on the GABA_A receptor complex.     

Anxiogenic-like action of caerulein,a CCK-8 receptor agonist,in the mouse: influence of acute and subchronic diazepam treatment

Summary Effects of caerulein, a cholecystokinin octapeptide (CCK-8) receptor agonist, on exploratory activity of mice were investigated. Exploratory and locomotor activity of animals were measured using elevated plus-maze and open field tests. The systemic administration of caerulein at nonsedative doses (100 ng/kg-1 µkg i. p.) resulted in a significant decrease in the exploratory activity of mice. This effect was completely blocked by proglumide, a CCK-8 antagonist (15 mg/kg i. p.), indicating the participation of CCK-8 receptors. Acute treatment with low doses (0.1–0.75 mg/kg i. p.) of diazepam did not attenuate the anxiogenic-like effect of caerulein, but at more high doses of diazepam the coadministration depressed locomotor activity in mice. After subchronic diazepam treatment (2.5 mg/kg once a day, 10 days, i.p.) tolerance was developed toward the sedative effect of diazepam, and 72 h after withdrawal of the drug the animals showed increased anxiety in the plus-maze test. 30 min after the last injection procedure the anxiogenic-like effect of caerulein (500 ng/kg i. p.) on exploration was absent in both diazepam or vehicle groups. However, 72 h after the last pretreatment injection caerulein (500 ng/kg i. p.) reduced significantly the exploratory activity in control group, whereas it was inactive after diazepam withdrawal. The results obtained in this study support the hypothesis that endogenous CCK-8 an CCK-8 receptors are involved in the neurochemistry of anxiety and the anxiolytic action of benzodiazepine tranquillizers. Send offprint requests to: J. Harro at the above address     

The role of delta opioid receptors in the anxiolytic actions of benzodiazepines

The anxiolytic effects of benzodiazepines appear to involve opioid processes in the amygdala. In previous experiments, overexpression of enkephalin in the amygdala enhanced the anxiolytic actions of the benzodiazepine agonist diazepam in the elevated plus maze. The effects of systemically administered diazepam are also blocked by injections of naltrexone into the central nucleus of the amygdala. The current studies investigated the role of delta opioid receptors in the anxiety-related effects of diazepam. Three days following bilateral stereotaxic injections of viral vectors containing cDNA encoding proenkephalin or beta-galactosidase (control vector), the delta opioid receptor antagonist naltrindole (10 mg/kg, s.c.) attenuated the enhanced anxiolytic effects of 1-2 mg/kg diazepam in rats overexpressing preproenkephalin in the amygdala. Despite this effect, naltrindole failed to attenuate the anxiolytic action of higher diazepam doses (3 mg/kg) in animals with normal amygdalar enkephalin expression. Similarly, the mu opioid receptor antagonist, beta-funaltrexamine (20 mg/kg, s.c.), had no effect on the anxiolytic effect of diazepam alone. These data support a role for delta opioid receptors in the opioid-enhanced anxiolytic effects of diazepam.     

The GABA(A) receptor mediates the hypnotic activity of melatonin in rats

The present investigation assessed whether hypnotic activity of melatonin was mediated by the GABA(A) receptor in rats. Electroencephalography (EEG) was measured in this experiment. Melatonin, at a dose of 10 mg/kg ip, showed a significant sleep-promoting effect in rats. Flumazenil (3.5 and 7 mg/kg), a specific antagonist of the benzodiazepine (BZP) recognition site on the GABA(A) receptor, and picrotoxin (2 and 4 mg/kg), the ligand of the picrotoxin site on the GABA(A) receptor, seemed to be devoid of intrinsic influence on each sleep parameter when used alone, but they significantly antagonized the melatonin-induced increase in total sleep time (TS), slow-wave sleep time (SWS) and paradoxical sleep time (PS), and the decrease in time to sleep onset (TSO) and wakefulness time (W). A significant interaction was shown between melatonin and flumazenil or picrotoxin. When bicuculline methiodide (2 and 4 mg/kg), a specific antagonist of the GABA binding site on the GABA(A) receptor, was used together with melatonin, the melatonin-induced increase in TS, SWS and PS, and the decrease in W were abolished. However, there was no interaction between melatonin and bicuculline methiodide on sleep parameters except PS. These results indicate that the hypnotic activity of melatonin may be linked to the GABA(A) receptor and mediated through the BZP recognition site, the picrotoxin site on the GABA(A) receptor and partially through the GABA binding site on the GABA(A) receptor.     

Ethanol-induced locomotor stimulation in C57BL/6 mice following RO15-4513 administration

The purpose of this study was to examine the effects of two partial benzodiazepine inverse agonists, RO15-4513 and FG-7142, alone and in combination with ethanol on locomotor activity in C57BL/6 mice. When administered alone, 1.5 g/kg ethanol did not significantly influence activity, confirming previous reports indicating this mouse strain is relatively insensitive to the excitatory properties of ethanol. RO15-4513 treatment also did not significantly influence locomotor activity when administered alone. However, coadministration of RO15-4513 (1.5–6 mg/kg) and ethanol markedly increased locomotor activity. Moreover, the unmasking of ethanol's stimulant action by RO15-4513 (6 mg/kg) was completely reversed by pretreatment with the benzodiazepine receptor antagonist RO15-1788. In contrast, FG-7142 (10–20 mg/kg) increased activity to the same extent in both saline and ethanol-injected mice. This effect was blocked by RO15-1788 pretreatment as well. Neither RO15-4513, FG-7142, nor RO15-1788 significantly influenced blood ethanol concentrations. It is suggested that RO15-4513 unmasked the stimulant effects of ethanol by virtue of its ability to antagonize the depressant properties of ethanol in C57BL/6 mice.     

Interactions of the imidazodiazepine Ro 15-4513 with chemical convulsants.

1. The proconvulsant effects of the imidazodiazepine Ro 15-4513, were investigated in mice by use of intravenous infusion of a variety of convulsant drugs. 2. Dose-response and time course studies of Ro 15-4513 against gamma-aminobutyric acid (GABA) antagonists were performed. On the basis of these studies a maximally effective dose of 5 mg kg-1 was administered 5 min before the determination of seizure thresholds in subsequent experiments. 3. Ro 15-4513 (5 mg kg-1) significantly lowered seizure thresholds to pentylenetetrazole, bicuculline and the convulsant benzodiazepine Ro 5-3663, but failed to alter seizure thresholds to picrotoxin, strychnine, caffeine and quipazine. 4. Ro 15-4513 significantly raised seizure threshold to the benzodiazepine receptor inverse agonist methyl 6,7-dimethoxy-4 ethyl-beta-carboline-3-carboxylate (DMCM). 5. These results are discussed in relation to other studies investigating the proconvulsant and alcohol-antagonizing effects of Ro 15-4513.     

Interaction of GABA and serotonin in the anxiolytic action of diazepam and serotonergic anxiolytics.

The general purpose of the present study was to analyze the possible interactions between the GABA-benzodiazepine and the serotonergic (5-HT) systems in the anxiolytic action of diazepam and the 5-HT1A agonists, ipsapirone, indorenate, and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The effect of the benzodiazepine receptor antagonist, flumazenil (10.0 mg/kg), on the anxiolytic action of ipsapirone (5.0 mg/kg), indorenate (5.0 mg/kg), and 8-OH-DPAT (0.125 mg/kg) was examined on the avoidance exploratory behavior paradigm in mice. The effect of the 5-HT1 blockers, methiotepin (0.31 mg/kg), pindolol (3.1 mg/kg), and alprenolol (5.0 mg/kg), on the anxiolytic action of diazepam (0.5 mg/kg) was also studied. In the last part of this work, the putative potentiation between diazepam (0.25 mg/kg) and each of the serotonergic anxiolytics was investigated. The antianxiety effect of diazepam, ipsapirone, indorenate, and 8-OH-DPAT was prevented by flumazenil. The serotonergic/beta-blocker, alprenolol, partially antagonized the diazepam effect. Finally, a potentiation of suboptimal doses of diazepam and ipsapirone, but not with indorenate or 8-OH-DPAT, was observed. The findings suggest an interaction between both systems on the anxiolytic action of diazepam and the 5-HT1A agonists.     

Participation of GABA--benzodiazepine receptor complex in the anxiolytic effect of piracetam

It is established that bicuculline, picrotoxin, and flumazenil (agents blocking different sites of GABA receptor) decrease the anxiolytic effect of piracetam as manifested in the conflict situation test. The most pronounced interaction was observed between piracetam and flumazenyl. On the background of antagonist action, piracetam inhibited the effects of flumazenil (but not those of bicuculline and picrotoxin). Based on these data, it is assumed that the anxiolytic effect of piracetam is mediated to some extent by benzodiazepine site of the GABA-benzodiazepine receptor complex.     

Effects of drugs acting on the GABA-benzodiazepine receptor complex on flurothyl-induced seizures in Mongolian gerbils

In the present study, the mechanism behind flurothyl-induced seizures was examined using drugs acting on the GABA-benzodiazepine receptor complex in Mongolian gerbils. In addition, amino acid concentrations in the brain were also investigated. In behavioral experiments, the incidence of tonic extensor was 83.3% in both the control and picrotoxin (0.5 mg/kg)-treated groups, 0% in the valproate (200 mg/kg)-treated group, and 50% in the picrotoxin plus valproate-treated group. However, picrotoxin did not antagonize the effect of valproate on clonic seizure latency at all. Flumazenil, a benzodiazepine receptor antagonist, was found to have an inhibitory effect on the anticonvulsant action of diazepam (0.5 mg/kg). The incidence of tonic extensor was 83.3% in flumazenil (10 mg/kg)-treated group, 0% in the diazepam (0.5 mg/kg)-treated group, and 83% in the flumazenil plus diazepam-treated group as well as the control group. Flumazenil also completely reversed the effect of diazepam on clonic seizure latency. In biochemical experiments, the concentration of the inhibitory amino acid, GABA, was significantly increased in the hippocampus (P<0.05) and cerebellum (P<0.01) in diazepam-treated animals. The increase of GABA in the hippocampus and cerebellum was antagonized by the administration of flumazenil. These results suggested that the anticonvulsant action of diazepam may be linked to increase in hippocampus and cerebellum GABA concentrations. The findings suggest that the mechanism of flurothyl-induced seizures, in part, is related to the highly sensitive benzodiazepine site of the GABA-benzodiazepine receptor complex.     

Ethopharmacology of maternal aggression in mice: effects of diazepam and SM-3997.

The present study investigated whether there is any difference between the effects of benzodiazepine and non-benzodiazepine anxiolytics on maternal aggression in lactating mice, using an ethological technique. We used SM-3997, a 5-HT1A receptor ligand, as a non-benzodiazepine anxiolytic. Behavior towards an intruder male mouse was assessed on postpartum days 5 and 7 in female mice that had been housed alone since the end of the 4-day mating period. Acute oral administration of diazepam had a biphasic effect on the frequency of bites: 1 mg/kg diazepam significantly increased bite frequency, while 2.5 mg/kg diazepam significantly decreased it. However, 2.5 mg/kg diazepam also caused a significant decrease in locomotor activity. In contrast, SM-3997 (1, 2.5 and 5 mg/kg p.o.) significantly decreased the frequency of bites in a dose-dependent manner without causing motor dysfunction. Chronic treatment with 5 mg/kg SM-3997 significantly decreased the frequency of bites when compared with vehicle, whereas diazepam was ineffective at the doses used (0.5 and 1 mg/kg p.o.). The findings suggest that the proaggressive effect is specific to benzodiazepines, and that 5-HT1A receptors may be involved in the suppression of maternal aggression in mice.     

A fully automated light/dark apparatus useful for comparing anxiolytic agents

The effects of known anxiolytic agents and putative anxiolytic agents were assessed in mice in a fully automated 2-compartment light/dark test. Significant increases in lit area activities (e.g., time spent in the lit area, locomotor activity, rearing behavior) were used as possible indicators of anxiolytic-like action. The measurement found most consistent and useful for assessing antianxiety-like activity was the time mice spent in the lit area. The benzodiazepine, diazepam; the 5-HT1A agent, ipsapirone; and the 5-HT3 receptor antagonist, ondansetron, produced significant anxiolytic-like activity between doses of 1.0 to 10.0 mg/kg, 17.8 to 31.6 mg/kg, and 0.0001 to 1.0 mg/kg respectively. The 5-HT1A receptor agonist, 8-OH DPAT, also exhibited anxiolytic-like action between doses of 0.0005 to 3.16 mg/kg. In contrast, the peripheral 5-HT3 receptor agonist, N-phenylbiguanide; the antidepressant, imiprame; the neuroleptic, chlorpromazine; and the CNS stimulat, S(+)-amphetamine, did not display antianxiety-like activity. The positive results obtained for the three types of compounds (benzodiazepine, 5-HT1A, and 5-HT3) indicate that this fully automated light/dark apparatus may be useful for identifying known and putative anxiolytic agents.     

Interactions of Ro 15-4513 with diazepam, sodium pentobarbital and ethanol in a holeboard test

Ro 15-4513 (1.5 mg/kg) decreased the exploratory activity of mice in a holeboard test. This effect was reversed by diazepam (1 mg/kg), ethanol (1 g/kg) and sodium pentobarbital (15 mg/kg). Higher doses of these three agents reduced the number of exploratory head-dips, and Ro 15-4513 antagonised these effects. These observations are consistent with the suggestion that Ro 15-4513 is a partial inverse agonist at benzodiazepine receptors and acts by reducing the efficacy of GABA. Ro 15-4513's interaction with ethanol in the holeboard closely resembled its interaction with the barbiturate.     

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.     

Evaluation of the Anticonvulsant and Anxiolytic Potentials of Methyl Jasmonate in Mice

Methyl jasmonate (MJ) is one of the most well-studied plant stress hormones belonging to the jasmonate family. Previous studies have shown that MJ potentiated pentobarbitone sleeping time and enhanced GABA-mediated inhibitory neurotransmission, suggesting potential benefits in disorders associated with hyperactivity of the brain. This study was carried out to evaluate whether MJ has anticonvulsant and anxiolytic properties in mice. The anticonvulsant effect was assessed based on the prevention of tonic-clonic seizures induced by chemoconvulsant agents in mice. The anxiolytic property was evaluated utilizing the elevated plus maze (EPM) and light/dark transition paradigms. The effect of MJ on spontaneous locomotor activity (SMA) was also assessed. Mice received intraperitoneal (i.p.) injections of MJ 30 min before the tests were carried out and diazepam (2 mg/kg, i.p.) was used as the reference drug. MJ (50–400 mg/kg) did not protect the mice against tonic-clonic convulsions induced by picrotoxin (10 mg/kg, i.p.) or strychnine (3 mg/kg, i.p.). However, MJ (100, 200, and 400 mg/kg) offered 20, 60, and 100% protection against pentylenetetrazole (100 mg/kg, i.p.)-induced convulsions. In a similar manner to diazepam (2 mg/kg), MJ (400 mg/kg) produced a marked sedative effect as shown by decreases in the number of lines crossed and the duration of ambulation in the open field test. In contrast to diazepam (2 mg/kg), MJ (5–50 mg/kg) did not show anxiolytic effects in the EPM and light/dark transition paradigms. These findings suggest that methyl jasmonate at high doses possessed anticonvulsant properties in the pentylenetetrazole animal model of epilepsy, but did not produce anxiolytic activity in mice.     

RO15-4513 antagonizes the anxiolytic effects of ethanol in a nonshock conflict task at doses devoid of anxiogenic activity.

RO15-4513 is a partial benzodiazepine inverse agonist that has been reported to antagonize some of the biochemical and neurobehavioral actions of ethanol. However, whether this antagonistic action of RO15-4513 is dependent on the drug exerting its intrinsic (inverse agonist) properties is unclear at present. The purpose of the present study was to examine whether RO15-4513 was capable of antagonizing the anxiolytic effects of ethanol in a nonshock conflict task at doses that, by themselves, do not reveal the compound's intrinsic anxiogenic properties. The consummatory conflict task employed (negative contrast) involves quantifying how animals respond to an abrupt, unexpected reduction in reward (sucrose solution), and is particularly sensitive to the effects of anxiolytic agents, including ethanol. As previously demonstrated, depressed consummatory behavior engendered by reward reduction was significantly alleviated by ethanol (0.75 g/kg). This anxiolytic effect of ethanol, however, was antagonized dose dependently by RO15-4513 (0.1875-3.0 mg/kg). Only the highest dose of RO15-4513 (3.0 mg/kg) showed evidence of further response suppression. Lower doses of RO15-4513 tested did not exert an anxiogenic effect when given alone. Thus the antagonism of EtOH's anxiolytic (contrast-reducing) effects occurred at doses of RO15-4513 (0.375-1.5 mg/kg) that did not exhibit any intrinsic anxiogenic activity. As such, these results suggest that RO15-4513 interacts with the anxiolytic effects of ethanol in a nonadditive fashion in this test situation.     

Anxiolytic-like effect of asiaticoside in mice

The putative anxiolytic activity of asiaticoside was examined in male mice by using a number of experimental paradigms of anxiety, with diazepam being as a positive anxiolytic control. In the elevated plus-maze test, diazepam (1 and 2 mg/kg) or asiaticoside (5 or 10 mg/kg) increased the percentage of entries into open arms and of time spent on open arms. In the light/dark test, as with 1 mg/kg diazepam, asiaticoside (10 and 20 mg/kg) increased the time spent in the light area and the movement in the light area without altering the total locomotor activity of the animals. In the hole-board test, asiaticoside at 10 mg/kg significantly increased head-dipping counts and duration as well as diazepam (0.3 mg/kg). Thus, these findings indicated that asiaticoside exhibited an anxiolytic-like effect. Further studies will be required to assess the generality of present findings to other species and behavioural paradigms.     

The effects of Ro 15-4513 on the behavioral actions of ethanol in an operant reaction time task and a conflict test

Ro 15-4513, an analogue of the benzodiazepine receptor antagonist Ro 15-1788, has been reported to selectively block the anxiolytic and intoxicating properties of ethanol in rats. To examine the specificity and selectivity of this ethanol antagonism, the effects of Ro 15-4513 were tested on the actions of ethanol in an operant reaction time and conflict test in rats. The operant reaction time task involved holding down a lever for 0.25-2.0 seconds to obtain food, and animals treated with 1 g/kg of ethanol showed a significant disruption in performance. This disruptive effect was reversed by Ro 15-4513 in doses of 1.5-5.0 mg/kg. Ro 15-4513 was also tested in an operant conflict paradigm sensitive to alcohol effects. Ro 15-4513 (0, 1.5, 3.0, 6.0 mg/kg) produced a significant decrease in both punished and unpunished responding in the conflict test. Ethanol (0.75 g/kg), pentobarbital (5 mg/kg) and chlordiazepoxide (5 mg/kg) all produced a significant release of punished responding that was blocked by pretreatment with 6.0 mg/kg Ro 15-4513, but again Ro 15-4513 suppressed responding on its own at this dose. These results suggest that Ro 15-4513 has inverse agonist properties that may explain its ethanol-antagonist action.