Effects of acute and chronic administration of the antidepressants, imipramine, phenelzine and mianserin, on the social behaviour of mice

Development and validation of a QuEChERS-HPLC-DAD method using polymer-functionalized melamine sponges for the analysis of antipsychotic drugs in milk

The prohibition of antipsychotic drugs in animal foodstuffs has raised significant concerns. In this study, a novel matrix purification adsorbent comprising a polymer (polyaniline and polypyrrole)-functionalized melamine sponge (Ms) was employed for the high performance liquid chromatography-diode array detector (HPLC-DAD) detection of three phenothiazines (chlorpromazine, thioridazine, and promethazine), and a tricyclic imipramine in milk. The as-prepared functionalized Ms was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. Excellent linearity with a coefficient of determination (R2) of 0.999 was achieved for all drugs within the concentration range of 0.01-47.00 μg mL-1. The recoveries of the four analytes ranged from 92.1 % to 106.9 % at the three spiked levels. These results demonstrate the successful application of the proposed method for the determination of the four drugs. Cost-effective polymer-functionalized Ms is a viable alternative for matrix purification, enabling rapid determination of drug residues in diverse food samples.

Long-term anxiolytic and antidepressant-like behavioural effects of tiagabine, a selective GABA transporter-1 (GAT-1) inhibitor, coincide with a decrease in HPA system activity in C57BL/6 mice

Gamma-aminobutyric acid (GABA) system plays a pivotal role in the pathophysiology of anxiety and mood disorders. This study was aimed to assess the anxiolytic and antidepressant-like properties of tiagabine, an inhibitor of the GABA transporter-1 (GAT-1), after acute and chronic administration in C57BL/6JOlaHsD mice with paroxetine as a positive control. In first experiments, the acute administration of tiagabine (7.5 mg/kg, orally [PO]) and paroxetine (10 mg/kg PO) induced anxiolytic effects in the elevated plus maze test and the modified hole board test and an antidepressant-like effect in the forced swim test. Chronic application of tiagabine (7.5 mg/kg PO) and paroxetine (10 mg/kg PO) for 22 days revealed an anxiolytic and antidepressant-like efficacy of tiagabine only. In a further experiment, we analysed the impact of chronic tiagabine versus paroxetine treatment on the hypothalamic-pituitary-adrenocortical (HPA) system regulation. GAT-1 blockade induced a setpoint-shift of the stress hormone system toward lower levels as indicated by decreased plasma corticosterone concentrations and attenuated gene expression levels of corticotropin-releasing factor in the paraventricular nucleus of the hypothalamus and of hippocampal steroid receptors. This data indicate that both acute and long-term anxiolytic and antidepressant-like properties of brain GAT-1 inhibition coincide with a reduction in HPA system activity in mice.

Biochemical, behavioral, physiologic, and neurodevelopmental changes in mice deficient in monoamine oxidase A or B

The availability of mutant mice that lack either MAO A or MAO B has created unique profiles in the central and peripheral availability of serotonin, norepinephrine, dopamine, and phenylethylamine. This paper summarizes some of the current known phenotypic findings in MAO A knock-out mice and contrast these with those of MAO B knock-out mice. Differences are discussed in relation to the biochemical, behavioral, and physiologic changes investigated to date, as well as the role played by redundancy mechanisms, adaptational responses, and alterations in neurodevelopment.

Measurement of anxiety in transgenic mice

A wide range of approaches has been used to study anxiety in mice. All presuppose that aversive stimuli, such as foot shock or novelty, induce a central state of fear, which can be quantified through specific behavioural and physiological measures. This review discusses the validity of the various approaches in terms of their similarity to different human anxiety disorders, their ability to detect compounds which modulate human anxiety, and their relevance to animal defensive processes. The most commonly used models of anxiety suitable for screening transgenic and knockout mice are discussed, with an emphasis placed on controlling for factors which could confound results. As all models used to date have limitations and no single paradigm adequately models all aspects of anxiety, this review recommends the use of a broad range of anxiety models in order to provide a comprehensive characterisation of the behavioural phenotype of transgenic mice.

Effects of rolipram on the elevated plus-maze test in rats: a preliminary study

The objective of the present study was to assess the behavioural effects of rolipram, a specific cAMP phosphodiesterase (PDE4) inhibitor, in the elevated plus-maze (EPM) test in rats. Results showed that rolipram at the highest dose tested (0.1 mg/kg) increased the percentage of both time spent and entries into open arms, although a decrease of locomotor activity in the EPM test was also observed. In contrast, diazepam (3.0 mg/kg) exhibited the typical profile of an anxiolytic in the EPM test, increasing the percentage of time spent and entries into open arms as well as locomotor activity. A posterior statistical analysis, however, established that the effects of both rolipram and diazepam on parameters denoting anxiolytic-like activity were statistically independent from those reflecting locomotor activity reduction. Furthermore, the effects of both rolipram and diazepam were shown to be distinct from those exhibited by tricyclic antidepressant imipramine which did not show any anxiolytic-like effects in the EPM test, although a reduction of locomotor activity was also detected. Although these preliminary results suggest that rolipram may have some anxiolytic-like properties on the EPM test in rats, such an interpretation should be taken cautiously due to the observed effects on locomotor activity, which could complicate the interpretation of results from rolipram and other PDE4 inhibitors in the current test and in other anxiety animal models.

Effects of chronic antidepressants in an operant conflict procedure of anxiety in the rat

The effects of chronic antidepressants were investigated in an animal procedure for the study of anxiety and anxiolytics, the conditioned suppression of operant behavior in rats. In daily 18-min sessions, three periods of nonpunished lever pressing for food alternated with two 4-min periods signaled by a light-on conditioned stimulus during which 50% of the responses were randomly punished by electric foot shocks. Antidepressants were administered once daily for 7-8 weeks to trained, food-restricted rats. Desipramine (dose regimen increase from 4 to 16 mg/kg/day) induced a gradual (4-5-week latency) release of response suppression during punished periods over the course of several weeks of testing. This anxiolytic-like effect was still present 3 weeks following drug discontinuation. In contrast, chronic imipramine (dose regimen increase from 4 to 16 mg/kg/day), maprotiline (4 to 16 mg/kg/day), phenelzine (2 to 4 mg/kg/day), and fluoxetine (1 or 8 mg/kg/day; constant dose), resulted in no change in punished responding, suggesting that no anxiolytic-like effect developed in the course of chronic treatment with these compounds. The largest dose of all antidepressants studied (except fluoxetine) induced a moderate to marked reduction of nonpunished performance that disappeared within 1 week after the last injection. A transient release of conditioned response suppression emerged during the week that followed discontinuation of imipramine, maprotiline, and fluoxetine (8 mg/kg/day). This apparent anxiolytic-like activity might be due to a reduction of some adverse effect induced by the high doses used, and/or might have resulted from a new dynamic equilibrium between monoamine release, reuptake processes, and sensitivity of postsynaptic receptors. In conclusion, operant conflict procedures in rats seem not particularly able to model human anxiety sensitive to chronic antidepressant treatments.

Corticotropin-releasing factor and defensive withdrawal: inhibition of monoamine oxidase prevents habituation to chronic stress

There is growing evidence for a role of extrahypothalamic corticotropin-releasing factor (CRF) in the pathogenesis of anxiety. A modified form of the defensive withdrawal test was used to test the anxiogenic effects of acute administration of intracerebroventricular (1 microg, i.c.v.) CRF in adult male rats. Habituation to the mild stress of daily handling and subcutaneous (s.c.) saline injection over 2-6 weeks abolished the anxiogenic effects of exogenous CRF. At 6 weeks this habituation also resulted in attenuation of baseline withdrawal behavior. CRF receptor binding was significantly decreased in the amygdala of chronically handled animals and may have been responsible for this habituation phenomenon. Comparison of rats treated with the monoamine oxidase (MAO) inhibitor, phenelzine [3 mg/kg, s.c., daily for 2-6 weeks] to the saline-treated groups revealed a failure to habituate to the chronic handling, as the baseline withdrawal (after injection of artificial CSF) by the phenelzine-treated animals was not different from the baseline withdrawal by unhandled rats. In comparison to rats treated chronically with saline, phenelzine treatment enhanced the anxiogenic effect of CRF. In summary, habituation to a mild chronic stress decreased baseline defensive withdrawal. Intraventricular administration of CRF produced an anxiogenic response as measured in the defensive withdrawal test, which was lost through exposure to mild chronic stress. Two or 6 weeks of daily handling and SC saline injection caused a downregulation of CRF receptors in the amygdala, which could account for the behavioral habituation and the loss of CRF-induced defensive withdrawal. Phenelzine treatment concurrent with mild chronic stress prevented habituation and maintained the anxiogenic effect of CRF in spite of the downregulation of CRF receptors in the amygdala.

Behavioural effects in mice of subchronic chlordiazepoxide, maprotiline, and fluvoxamine. I. Social interactions

The present study compares the effects of subchronic administration (daily. 21 days) of chlordiazepoxide (CD), maprotiline and fluvoxamine on the behavior of male mice during dyadic social interactions. Maprotiline like chlordiazepoxide, stimulated aggression at 4 mg/kg and 2 mg/kg respectively (intermediate dose levels), whereas effects of fluvoxamine (3-8 mg/kg) were mainly sedative. Non-social activity was reduced by CD at 4 and 8 mg/kg and by maprotiline at 0.5 mg/kg. At the highest dose tested (10 mg/kg), maprotiline increased immobility, resembling the effects of fluvoxamine, while at 2 mg/kg, it reduced social investigation. Thus, despite some commonalities, there were several differences in behavioral profile of the compounds tested. Data are discussed in relation to the efficacy of each of these compounds in treating anxiety and depressive disorders.

Behavioural effects in mice of subchronic chlordiazepoxide, maprotiline and fluvoxamine. II. The elevated plus-maze

In view of apparent commonalities in the aetiology, symptomatology, and pharmacotherapy of anxiety and depressive disorders, the present study compares the effects of the benzodiazepine, chlordiazepoxide (1.0-8.0 mg/kg), the selective noradrenaline (NA) reuptake inhibitor, maprotiline (0.5-10.0 mg/kg), and the serotonin (5-HT)-selective reuptake inhibitor, fluvoxamine (2.0-8.0 mg/kg), on the behaviour of mice in the elevated plus-maze test of anxiety. To more accurately reflect the clinical situation, subjects were treated daily for 21 days prior to testing, and comprehensive behavioural profiles were obtained through the application of an ethological scoring technique. Results show that subchronic treatment with chlordiazepoxide produced clear anxiolytic-like effects at the highest dose tested, coupled with an inhibition of risk assessment over the entire dose range. With the exception of risk assessment measures, anxiolytic-like effects were also seen with a low dose (0.5 mg/kg) of maprotiline: these effects were lost at higher doses. In contrast to these data, fluvoxamine produced minimal behavioural change under present test conditions. Findings are discussed in relation to the relative efficacy of selective monoamine. reuptake inhibitors in the treatment of anxiety disorders, and the nature of anxiety evoked in mice by exposure to the elevated plus-maze.

The antidepressant drug phenelzine produces antianxiety effects in the plus-maze and increases in rat brain GABA

Research on the effects of antidepressant/ antipanic drugs in animal models of anxiety has yielded equivocal results, even after chronic drug regimens. In contrast, we found that the antidepressant/antipanic drug phenelzine, given acutely, produced a clear anxiolytic effect in the elevated plus-maze, a widely-used animal model of "anxiety" that is primarily sensitive to benzodiazepine-type anxiolytics (e.g., diazepam). Furthermore, the effective dose of phenelzine (15 mg/kg) administered to rats was associated with more than a 2- fold increase in whole brain levels of gamma-aminobutyric acid (GABA), whereas an ineffective dose of phenelzine (5.1 mg/kg) did not significantly change GABA levels. The N-acetylated metabolite of phenelzine, N2-acetylphenelzine, produced neither an anxiolytic effect in the elevated plus-maze nor a significant change in whole-brain levels of GABA. However, both phenelzine and N2-acetylphenelzine potently inhibited monoamine oxidase, a mechanism commonly thought to be involved in the therapeutic effects of monoamine oxidase inhibitors such as phenelzine in the treatment of depression in humans. These results suggest that the mechanism whereby phenelzine produces anxiolytic effects in the plus-maze model is unique to a facilitatory action on brain levels of GABA, in contrast to classical benzodiazepines, which produce anxiolytic effects by enhancing the affinity of the GABAA-receptor for GABA.

Endotoxin produces a depressive-like episode in rats

Activation of the immune system produces psychological and physiological effects, which resemble the characteristics of depression. The present study was designed to investigate further, in rats, the similarity between the behavioral effects of immune activation and a model of depression in animals. Reduction in the preference for and consumption of saccharin solutions and suppression of sexual behavior were used as models of one essential feature of depression, the inability to experience pleasure (anhedonia). Other measures testing this model were the reduction in food consumption, body weight, locomotor activity, and social interaction. It was found that systemic injection of lipopolysaccharide (endotoxin), which is a potent activator of the immune system, significantly decreased saccharin preference in fluid-deprived rats. Lipopolysaccharide (LPS) also decreased free consumption of saccharin, but not water, in non-deprived rats. Several indices of male sexual behavior were significantly suppressed following LPS administration. Chronic, but not acute, treatment with the tricyclic antidepressant imipramine abolished the suppressive effect of LPS on saccharin preference. Moreover, chronic, but not acute, treatment with imipramine also reduced and facilitated the recovery from the suppressive effects of LPS on food consumption, body weight, social interaction and activity in the open-field test. The results suggest that activation of the immune system in rats produces anhedonia and other depressive-like symptoms, which can be attenuated or completely blocked by chronic treatment with an antidepressant drug.

Ethological comparison of the effects of diazepam and acute/chronic imipramine on the behaviour of mice in the elevated plus-maze

Recent clinical evidence suggests that the tricyclic antidepressant imipramine is effective against not only panic disorder but also generalized anxiety disorder. Although most animal models of anxiety appear to be insensitive to this agent, such work has almost invariably employed an acute treatment regimen. In the present study, ethological methods have been used to assess in detail the effects of acute and chronic imipramine treatment on the behaviour of male DBA/2 mice in the elevated plus-maze test. In contrast to acutely administered diazepam (1 mg/kg), which produced a significant anxiolytic profile on standard and ethological measures, neither acute nor chronic (daily, 15 days) treatment with imipramine (0-20 mg/kg) was associated with anxiety reduction. Data are discussed in relation to test sensitivity factors and the nonspecific mechanism of action of imipramine.