Factors triggering abolishment of benzodiazepines effects in the Four-Plate Test--retest in mice.

Abolishment of anxiolytic-like effects of diazepam occurs during re-exposure to some animal tests of anxiety. We investigated the loss of anxiolytic-like effects of diazepam during Trial 2 on previously undrugged mice, namely one-trial tolerance (OTT). Swiss mice were subjected to 1) Four-Plate Test (FPT) without punishments in Trial 1 or 2) FPT without punishments in both Trials or 3) FPT with spatial modifications in Trial 1 or 4) Elevated Plus Maze (EPM), then 24 h later to FPT, with saline, diazepam (1 mg/kg) or DOI (1 mg/kg). Removing punishments in Trial 1 does not counteract the effect reduction of diazepam in Trial 2, but spatial modifications of the aversive environment. Previous exposure to EPM does not trigger a loss of efficacy of diazepam in FPT. Electric punishments do not trigger OTT to benzodiazepines; whilst knowledge of the environment seems to be responsible for this phenomenon. FPT may be useful to study OTT because punishments potentate OTT in this model of anxiety.

Role of ozone and granular activated carbon in the removal of mutagenic compounds.

The identification of certain organic compounds in drinking water has led water treatment specialists to be increasingly concerned about the eventual risks of such pollutants to the health of consumers. Our experiments focused on the role of ozone and granular activated carbon in removing mutagenic compounds and precursors that become toxic after chlorination. We found that if a sufficient dose of ozone is applied, its use does not lead to the creation of mutagenic compounds in drinking water and can even eliminate the initial mutagenicity of the water. The formation of new mutagenic compounds seems to be induced by ozonation that is too weak, although these mutagens can be removed by GAC filtration. Ozone used with activated carbon can be one of the best means for eliminating the compounds contributing to the mutagenicity of water. A combined treatment of ozone and activated carbon also decreases the chlorine consumption of the treated water and consequently reduces the formation of chlorinated organic compounds.

Drug mechanisms in anxiety.

The most common and successful therapyfor the majority of patients suffering from anxiety is treatment with benzodiazepines (BZDs). The problem of drug-induced dependency following treatment with these drugs may be avoided by developing more selective and specific BZD compounds, such as 2,3-substituted BZDs. Alternative approaches to the treatment of anxiety include the following: (i) antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), which are active in treating most anxiety disorders, including GAD; (ii) metabotropic glutamate (mGluR2) receptor agonists, which negatively modulate glutamate neurotransmission, and CRF antagonists, which have been proposed to exhibit anxiolytic properties; (iii) 5-HT1A receptor agonists which have demonstrated anxiolytic effects in clinical studies, although preclinical studies have reported weak or variable effects; (iv) 5-HT moduline antagonists, as well as 5-HT2C receptor antagonists, which may have anxiolytic properties; and, finally, (v) other approaches which are under investigation, including CCK2 antagonists.

The additive effects of quinine on antidepressant drugs in the forced swimming test in mice.

The aim of this study was to investigate if quinine plus antidepressant drugs (ADS) leads to an additive effect in the forced swimming test. Quinine (0.125, 0.5 mg/kg) and ADS (subactive doses) were given IP 45 and 30 min, respectively, before the test. When combined with QUIN, all drugs that act via inhibition of 5-HT uptake (imipramine, amitriptyline, citalopram, paroxetine, fluoxetine and fluvoxamine) significantly increased the swimming time of mice. Among trazodone, mianserin and iprindole (atypical ADS), only iprindole combined with quinine decreased the immobility (increased swimming) of the animals. The specific noradrenaline (NA) uptake inhibitors, desipramine and viloxazine, but not maprotiline, were also found to reduce the immobility time when pretreated with quinine. The mixed monoamine oxidase (MAO) inhibitor (pargyline) and MAO-A inhibitor (moclobemide) also shortened the period of immobility whereas the MAO-B inhibitor (nialamide) and the dopamine (DA) uptake inhibitor (bupropion) did not. Quinine's additive effects on several types of ADS is likely a result of blockade of potassium channels.

Additive effects of lithium and antidepressants in the forced swimming test: further evidence for involvement of the serotoninergic system.

In the mouse forced swimming test (FST) pretreatment with a subactive dose of lithium (1 mEq/kg), given IP 45 min before the test, facilitated the antidepressant activity of iprindole, fluoxetine, and moclobemide (given IP 30 min before the test). These antidepressants (ADS) were not active alone in the FST in this study. Moreover, when subactive lithium was combined with a wide range of ADS, each given at subactive doses, those ADS with serotoninergic properties (e.g. imipramine, citalopram, paroxetine, fluoxetine, trazodone, mianserin, and moclobemide) significantly reduced immobility times. ADS acting primarily on noradrenaline (NA) or dopamine (DA) systems (desipramine, maprotiline, viloxazine, and bupropion) did not significantly decrease immobility when given in combination with lithium. This was also the case for RO 16 6491 [a reversible, B specific monoamine oxidase inhibitor (MAOI)], nialamide, and pargyline (both irreversible, mixed MAOIs). The anti-immobility effect of iprindole in combination with lithium suggests either a direct or indirect action on the serotonin (5HT) system by this ADS whose mechanism of action remains obscure. These results, using an animal behavioral model of depression and combining our present knowledge of the acute action of various ADS, support the hypothesis that the potentiation by lithium of ADS is via direct 5HT mechanisms, indirectly via a NA/5HT link, and/or by second messenger systems. Lithium may also facilitate the expression of antidepressant activity of ADS not active by themselves in the FST.

Comparison of antidepressant activity in 4- and 40-week-old male mice in the forced swimming test: involvement of 5-HT1A and 5-HT1B receptors in old mice.

RATIONALE: A recent study suggested that selective serotonin reuptake inhibitors were inactive in 40-week-old male mice in the mouse forced swimming test, possibly because of alteration of 5-HT1 receptors. OBJECTIVES: The present study was aimed at investigating the action of various antidepressant drugs in 4- and 40-week-old male mice using the mouse forced swimming test and determining the involvement of 5-HT1A and 5-HT1B receptors mediating the effects. METHODS: Different classes of antidepressants [imipramine (tricyclic), maprotiline (noradrenline reuptake inhibitor), venlafaxine (mixed serotonin and noradrenaline reuptake inhibitors), fluvoxamine and sertraline (selective serotonin reuptake inhibitor)] were tested in the same randomised experimental session, alone and in combination with 5-HT1A and 5-HT1B receptor agonists [buspirone (partial 5-HT1A agonist), anpirtoline (5-HT1B agonist)] in the mouse forced swimming test. RESULTS: All antidepressants were found to be active in the mouse forced swimming test in 4-week-old mice and 40-week-old mice, with the exception of fluvoxamine in the 40-week-old mice. The anti-immobility effect after antidepressant administration was higher in 4-week-old male mice than in 40-week-old male mice. Venlafaxine is the most active antidepressant drug in 40-week-old mice. Prior administration of buspirone (0.06 mg/kg, i.p.) or anpirtoline (1 mg/kg, i.p.) enhanced the antidepressant-like effects in 4-week-old mice (except in the case of sertraline, 8 mg/kg). In elderly mice, only prior administration of buspirone enhanced the antidepressant-like effects of fluvoxamine. A neurochemical study showed that significantly higher serotonin and dopamine concentrations were found in 40-week-old control mice brains than 4-week-old control mice brains but that the noradrenaline concentration is higher in 4-week-old mice. CONCLUSION: Tricyclic, noradrenaline reuptake inhibitors and serotonin reuptake inhibitors are more active in 4-week-old mice than 40-week-old mice. Our results suggested that 5-HT1B receptors may be more altered than 5-HT1A receptors in 40-week-old mice.

Is dopamine implicated in the antidepressant-like effects of selective serotonin reuptake inhibitors in the mouse forced swimming test?

RATIONALE: Microdialysis, binding and behavioural studies have shown that the dopaminergic system plays a role in antidepressant treatment. OBJECTIVES: The present study determined whether the antidepressant-like effects of selective serotonin reuptake inhibitors measured in the mouse forced swimming test are mediated via dopamine receptors. METHODS: Male Swiss mice were randomly assigned to groups of 24 animals and injected IP with citalopram, fluoxetine, fluvoxamine, sertraline, or paroxetine alone or in combination with the dopamine D(1)agonist SKF 38393, the D(1) antagonist SCH 23390, the D(2) agonist bromocriptine, the D(2) antagonist sulpiride, the D(3) agonist PD 128 907, or the D(3) antagonist nafadotride. RESULTS: The anti-immobility effects of paroxetine, fluvoxamine and citalopram were increased by co-administration of SKF 38393 (0.5 and 2 mg/kg), SCH 23390 (0.06 mg/kg), bromocriptine (0.5 and 2 mg/kg) or PD 128 907 (1 and 2 mg/kg), and were attenuated by SCH 23390 (0.5 mg/kg). The anti-immobility effects of paroxetine and fluvoxamine were also increased with sulpiride (0.5 and 2 mg/kg). The anti-immobility effect of fluoxetine was increased by SKF 38393 (2 mg/kg) and PD 128 907(1 and 2 mg/kg) co-administration. The anti-immobility effect of sertraline (16 mg/kg) was increased by SKF 38393 (0.5 mg/kg), bromocriptine (2 mg/kg) and PD 128 907 (2 mg/kg) and the effect of sertraline (2 mg/kg) was increased by bromocriptine (2 mg/kg). The anti-immobility effect of paroxetine (4 mg/kg) was increased by nafadotride (2 mg/kg). CONCLUSIONS: These data indicate that the antidepressant activity of various SSRIs involves different dopamine receptor subtypes and that the serotoninergic and dopaminergic systems interact with each other.

Cyamemazine as an anxiolytic drug on the elevated plus maze and light/dark paradigm in mice.

Several studies have demonstrated that cyamemazine, a classic antipsychotic compound, possesses anxiolytic properties in humans as well as a potent antagonistic effect on 5-HT(2C) and 5-HT(3) receptors. In this study the level of anxiety of mice was assessed in the light/dark exploration test and the elevated plus maze (EPM) following both acute and chronic administration. Spontaneous locomotor activity was measured using a photoelectric actimeter. Acute or chronic administration of cyamemazine dramatically decreases the spontaneous locomotor activity of mice at the dose of 1 mg/kg in comparison with the control group. In the light/dark exploration test, cyamemazine (0.375 mg/kg) only demonstrated anxiolytic-like activity following acute administration. In the elevated plus maze (EPM), cyamemazine did not induce any anxiolytic like effects after acute administration. However, after chronic administration, cyamemazine at doses of 0.25, 0.375, 0.5 and 1 mg/kg significantly increased the time spent in the open arms. The number of open arm entries was also increased at 0.25 and 0.5 mg/kg. Various serotonergic ligands were then used to examine the role of the various receptors in mediating the effects of cyamemazine in the EPM. Concerning the 5-HT(2) ligands DOI and mCPP antagonised the effects of cyamemazine and N-desmethyl clozapine potentiated the effects. For 2-methyl-5-HT and ondansetron, the 5-HT(3) receptor ligands did not seem to have any effect. It appears that the 5-HT(2C) receptors are more implicated in the function of mediating the anxiolytic effect of cyamemazine in the EPM. The discrepancy of results obtained in the tests, following acute or chronic administration could be the result of the combined activity of dopamine D(2) receptor antagonism with antagonism of 5-HT(2C) and 5-HT(3) receptors.

Are there gender differences in the temperature profile of mice after acute antidepressant administration and exposure to two animal models of depression?

Numerous studies have reported gender differences in the rates of depression in humans, but few behavioural observations of antidepressant drug effects have been investigated in female mice. The forced swimming test (FST) is widely used as a predictor of antidepressant activity in rodents, as is the tail suspension test (TST), where immobility is objectively measured and in this last test, no hypothermia is induced by immersion in cold water. The present study investigated gender differences in the temperature profile of mice after acute antidepressant administration (imipramine and paroxetine) and exposure to two animal models of depression. Imipramine and paroxetine were active at 32 mg/kg in male mice in the FST, whereas they were active at 8, 16 and 32 mg/kg in female mice. In the TST, for both antidepressants immobility duration was reduced at a dose of 16 and 32 mg/kg in male mice and at 32 mg/kg in female mice. No significant difference was observed between male and female mice for immobility duration. Imipramine administration, but not paroxetine, decreased the temperature at the higher dose (32 mg/kg) in male and female mice in the FST. The body temperature was reduced in male and female mice for all treatment groups after FST challenge. Imipramine (16 and 32 mg/kg in male and 32 mg/kg in female mice), paroxetine (4, 16 and 32 mg/kg in male and 4 to 32 mg/kg in female mice) attenuated the reduction in temperature due to the FST. In the TST, imipramine tends to decrease the temperature in male and female mice, even though only imipramine at a dose of 32 mg/kg in female mice significantly decreases the temperature. Paroxetine had no effect on temperature. The TST enhanced the body temperature in male and female mice. In mice, there was no difference between the sexes after imipramine or paroxetine administration in the FST and TST. Both tests can be used to predict the activity of antidepressants as the decrease or enhancement of temperature is not correlated with a reduction in immobility duration.

Behavioral models in mice. Implication of the alpha noradrenergic system.

1. The mechanism of action of drugs might change according to the test used. Several noradrenergic drugs were tested in order to understand their implication in the mobility tests. 2. It was found that clonidine, an Alpha 2 agonist, acted differently according to the test used. It provoked sedation in spontaneous activity test, and anti-immobility effects in the other tests. 3. Tail suspension test is able to show the double acting of clonidine. 4. Idazoxan might act either as an alpha 2 antagonist or as partial alpha 2 agonist. TST shown the unexpected partial alpha agonist effect of the molecule. 5. Forced swimming test is more specific for predicting antidepressant activity than tail suspension test which is close to a spontaneous activity model.

Additive effect of lithium and clonidine with 5-HT1A agonists in the forced swimming test.

1. The aim of the present work was to demonstrate the possible additive effect of lithium and clonidine with 5-HT1a agonists in the forced swimming test. 2. Anti-depressant like effects of 5-HT1a agonists was investigated using forced swimming test. When administered alone, only 8-OH-DPAT reduced the immobility time in mice. 3. 5-HT1a agonists were then tested in combination with clonidine or lithium. Only gepirone and ipsapirone pretreated by either lithium or clonidine reduced immobility time in the forced swimming test. 4. The authors conclude that lithium and clonidine might be useful to predict antidepressant-like activity of new compounds.

The mouse light-dark paradigm: a review.

1. The light/dark paradigm is based on the innate aversion of rodents to brightly illuminated areas and on the spontaneous exploratory behaviour of the animals, applying mild stressors i.e. novel environment and light. The test apparatus consists of a small dark secure compartment (one third) and a large illuminated aversive compartment (two thirds). 2. The test was developed with male mice. The strain, weight and age may be crucial factors. 3. The extent to which an anxiolytic compound can facilitate the exploratory activity depends on the baseline level in the control group. Differences between the type and severity of external stressors might account for variable results reported by different laboratories. 4. In conclusion, the black and white test may be useful to predict anxiolytic-like or anxiogenic-like activity in mice. Transitions have been reported to be an index of activity-exploration because of habituation over time and the time spent in each compartment to be a reflection of aversion. Classic anxiolytics (benzodiazepines) as well as the newer anxiolytic-like compounds (e.g. serotonergic drugs) can be detected using this paradigm. It has the advantages of being quick and easy to use, without requiring the prior training of animals.

Evaluation of efficacies of different classes of antidepressants in the forced swimming test in mice at different ages.

1. The efficacies of different classes of antidepressants were investigated using the forced swimming test with mice at different ages. 2. Imipramine (4-32 mg/kg), desipramine (2-16 mg/kg) and bupropion (32, 64 mg/kg) showed activity in all age groups. 3. The selective serotonin reuptake inhibitors (SSRIs) citalopram (16 and 32 mg) and paroxetine (4 and 8 mg) were inactive in the oldest (40 weeks) group of mice, despite showing activity at the same doses in mice ranging in age from 4-24 weeks old. 4. Both SSRIs showed anti-immobility effects at low doses, (paroxetine: 1 and 2 mg/kg; citalopram: 4 and 8 mg/kg) in the 40-week old mice. These effects were not evident in the three younger groups of mice. 5. Moclobemide, a reversible selective inhibitor of monoamine oxidase-A, showed activity only at a high dose (128 mg/kg) and only in 12-week old animals. 6. Since SSRIs have been reported to have relatively selective effects on 5-HT1B receptors, the present results suggest that further studies comparing the effectiveness of SSRIs and other antidepressants in elderly patients should be done. Studies of the effects of aging on the density and/or affinity of 5-HT1A and 5-HT1B/1D receptors are also warranted.

A schematic representation of the psychopharmacological profile of antidepressants.

1. Using simple animal tests, "behavioural" and "biochemical" aspects of depression, anxiolysis, disinhibition, psychostimulation and sedation were investigated in mice using a variety of antidepressant drugs. 2. Dothiepin and mianserin (16 and 32 mg/kg), fluoxetine (32 and 64 mg/kg), maprotiline and imipramine (16, 32 and 64 mg/kg) and viloxazine (16 mg/kg) significantly potentiated mortality following acute administration with yohimbine. 3. Dothiepin and imipramine (32 mg/kg), fluoxetine (16 and 32 mg/kg), viloxazine (8 and 16 mg/kg), maprotiline (32 mg/kg) and mianserin (32 mg/kg) reduced immobility time in the forced swimming test. 4. In the black and white box, dothiepin (32 mg/kg) significantly increased the time spent in the bright compartment: Fluoxetine (8 and 16 mg/kg) significantly increased the number of crossings between compartments, an effect indicative of desinhibition. 5. It can be concluded that dothiepin possesses both antidepressant and anxiolytic properties in these animal models. The present procedure is useful not only for the screening of compounds that may possess antidepressant properties, but is also of value in determining other properties that may contribute to the overall clinical efficacy of the drugs.

Sigma ligand S14905 and locomotor activity in mice.

The binding and locomotor profile of a new sigma ligand, S14905, (isobutyl-N-(1-indan-2yl-piperid-4-yl)N-methyl carbamate, furamate) was studied. The binding data revealed that S14905 has a high affinity for sigma receptors and very low affinity for both dopamine D1 and D2 receptors. We have demonstrated that this sigma ligand prevents the locomotor stimulation induced by morphine (32 and 64 mg/kg), cocaine (16 mg/kg), amphetamine (4 mg/kg) and adrafinil (32 mg/kg) at doses lower than those required to depress spontaneous locomotor activity. The antagonism observed in the present study seems to be more specific of morphine induced hyperlocomotion. The high affinity of this compound for sigma receptors makes it a good choice to study the role of this receptor in the CNS. In addition, S14905 does not directly block dopamine receptors but may modulate them in some manner, and would thus warrant further study as a potential atypical antipsychotic agent, and an antagonist for the hyperactivity induced by opiate drug.

Differential effects of clonidine, lithium and quinine in the forced swimming test in mice for antidepressants: possible roles of serotoninergic systems.

The forced swimming test (FST) is a behavioral test used to predict the efficacy of antidepressant (AD) treatments. In the present study, it was found that, when combined with clonidine, lithium or quinine, subactive doses of several types of ADs (tricyclics, 5-HT uptake inhibitors and atypical ADs) produced anti-immobility effects in mice. Clonidine (0.06 mg/kg) was found to potentiate the AD-like effects of all the drugs tested in the FST. More interesting is the additivity of gepirone with lithium (1 mEq/l), and ondansetron with quinine (0.5 mg/kg). The results of the present study are in favour of the potentiation of AD activity by clonidine via 5-HT2 receptors, lithium through 5-HT1A receptors, and quinine through 5-HT3 receptors. Further studies to examine in detail which of these three 5-HT receptors or their subtypes is the most important in the actions of individual ADs are warranted.

5-HTP induced diarrhea as a carcinoid syndrome model in mice?

Serotonin (5-HT) is present in the gastrointestinal tract and is probably one of the compounds responsible for diarrhea in patients presenting with carcinoid syndrome. Intraperitoneal administration of L-5-hydroxytryptophan (L-5-HTP) at doses of 25 to 100 mg/kg dramatically increase defecation in mice. In this new paradigm, counting fecal boli deposited is simple and the appraised or inhibition of diarrhea induced by ip 25 mg/kg of L-5-HIP is very clear, with a good reproducibility of scores. L-5-HTP needs to be metabolized into 5-HT to be active; benserazide, an inhibitor of decarboxylase, antagonized the diarrhea induced by 5-HT. Among the 5-HT antagonists used in interaction with 5-HT, only these of the 5-HT3 type (ondansetron, granisetron, tropisetron) and, to a lesser extent 5-HT2 type (ritanserin), decreased the diarrhea induced by 5-HTP. The 5-HT4 receptor agonists from the benzamide family (metoclopramide and zacopride) increased defecation in mice but the effect failed to reach statistical significance.

Influence of age on behavioural response in the light/dark paradigm.

We have compared the performance of male Swiss mice at different ages (correlated with different body weight; 12-34 g) in the light/dark test of anxiety. Mice received saline only. The best age at which control values were optimum was that of 4 weeks old. Mice at this age spent 58% of the total test duration in the dark compartment. The oldest mice (i.e., 8 weeks old) exhibited an increase in total activity characterised by increase in movements in each compartment, together with an increase in the number of transitions. An age-related effect was found suggesting caution when interpreting the results of mice in the light/dark paradigm, the best period being that of 4 weeks.

Anti-conflict effect of 5-HT1A agonists in rats: a new model for evaluating anxiolytic-like activity.

A new conflict procedure was developed to study the potential anti-punishment effects of 5-HT( 1A) agonists as compared to diazepam. In this paradigm, the opportunity existed for rats to choose during punished periods between immediate, punished reinforcement and delayed, non-punished reinforcement. The results confirm that, for non-sedative doses (1 mg/kg), diazepam increases the number of punished responses. Furthermore, the present paradigm seems sensitive for the detection of 5-HT(1A) activity. Buspirone, gepirone, ipsapirone, zalospirone and 8-OH-DPAT increased responding for immediate but punished reinforcement. 1-(2-pyrimidinyl)piperazine, the common metabolite of the azapirones, does not participate in their anti-conflict effect. NAN 190, a 5-HT(1A) antagonist, was shown to block the 5-HT(1A) agonists. The findings of the present study suggest that benzodiazepines and 5-HT( 1A) agonists reduce the capacity to tolerate delays in reward. Abnormality in serotonin systems may be associated with poor impulse control.

A new approach to the light/dark test procedure in mice.

The effect of the known anxiolytic agents diazepam and alprazolam and a putative anxiogenic agent, FG 7142, were assessed in a fully automated and computer-integrated two-compartment light/dark apparatus. In addition, psychostimulant drugs (amphetamine, adrafinil, amineptine, and caffeine) were tested to determinate the influence of increasing locomotor activity on the indices of anxiety. Some modifications, such as using a soiled apparatus, have been made from the initial model to reduce any neophobic response to the test situation. These results have been compared to results obtained after cleaning between trials. In addition, strain differences have been assessed by comparing the effect of Swiss mice with the C57Bl/6J strain. The role of each parameter as an index of anxiety is discussed. The time spent in the lit area and exploratory behaviors seemed to be the most reliable parameter for assessing anxiolytic-like activity. Diazepam and alprazolam were found to have an anxiolytic profile. FG 7142 did not demonstrate any intrinsic effect. Amphetamine was reported to be anxiogenic, and amineptine, adrafinil, and caffeine only had a psychostimulant profile. We conclude that the light/dark test may be useful for identifying putative anxiolytic and anxiogenic agents, but an additional test such as an open field or an actimeter test must be performed as a control with regard to the problem of sedation and change in exploration. The Swiss strain of mice has been found a suitable strain to be used in the test.