Involvement of serotonin receptor subtypes in the antidepressant-like effect of beta receptor agonist Amibegron (SR 58611A): an experimental study

The role of mGluR5 on the therapeutic effects of ketamine in Wistar rats

RATIONALE

Ketamine produces dissociative, psychomimetic, anxiolytic, antidepressant, and anesthetic effects in a dose dependent manner. It has a complex mechanism of action that involve alterations in other glutamate receptors. The metabotropic glutamate receptor 5 (mGluR5) has been investigated in relation to the psychotic and anesthetic properties of ketamine, while its role in mediating the therapeutic effects of ketamine remains unknown.

OBJECTIVES

We investigated the role of mGluR5 on the antidepressant, anxiolytic and fear memory-related effects of ketamine in adult male Wistar rats.

METHODS

Two sets of experiments were conducted. We first utilized the positive allosteric modulator CDPPB to investigate how acute mGluR5 activation regulates the therapeutic effects of ketamine (10 mg/kg). We then tested the synergistic antidepressant effect of mGluR5 antagonism and ketamine by combining MTEP with a sub-effective dose of ketamine (1 mg/kg). Behavioral despair, locomotor activity, anxiety-like behavior, and fear memory were respectively assessed in the forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and auditory fear conditioning.

RESULTS

Enhancing mGluR5 activity via CDPPB occluded the antidepressant effect of ketamine without changing locomotor activity. Furthermore, concomitant administration of MTEP and ketamine exhibited a robust synergistic antidepressant effect. The MTEP + ketamine treatment, however, blocked the anxiolytic effect observed by sole administration of MTEP or the low dose ketamine.

CONCLUSIONS

These findings suggest that suppressed mGluR5 activity is required for the antidepressant effects of ketamine. Consequently, the antagonism of mGluR5 enhances the antidepressant effectiveness of low dose ketamine, but eliminates its anxiolytic effects.

Effects of mirabegron on depression, anxiety, learning and memory in mice

Mirabegron is the first b3-adrenoceptor agonist to enter clinical practice and has been approved for the treatment of symptoms of OAB. The aim of this study is to investigate whether the mirabegron has an effect on depression, anxiety, learning, and memory. We investigated the effects of mirabegron on depression, anxiety, learning and memory by using forced swimming test, elevated plus maze test, passive avoidance and Morris water maze in mice. Imipramine and mirabegron (3, 6 and 9 mg/kg) significantly reduced immobility time in forced swimming test. Diazepam and mirabegron (3, 6 and 9 mg/kg) significantly increased the time spent in open arms and the number of entries to the open arms in elevated plus maze test. Furthermore, cognitive performance impaired with scopolamine has been significantly improved with 9 mg/kg mirabegron. Mirabegron (6 and 9 mg/kg) significantly increased the time spent in the target quadrant in naive mice. While scopolamine significantly increased the swimming speed, mirabegron (9 mg/kg) significantly decreased the swimming speed in scopolamine-treated mice. Mirabegron might be clinically useful for the treatment of OAB in elderly patients that should use drugs against depression and anxiety, without disrupt learning and memory.

Effects of long-term treatment with haloperidol, clozapine and aripiprazole on mice isolated vas deferens

PURPOSE

Sexual dysfunction is a common condition in patients taking antipsychotics and is the most bothersome symptom and adverse drug effect, resulting in a negative effect on treatment compliance. Pharmacology research into human ejeculatory disorders is limited to clinical studies with registered drugs affecting the ejaculation process; therefore, animal research has become the need. We aimed to investigate the effects of haloperidol, clozapine and aripiprazole on serotonin, noradrenaline, adenosine triphosphate (ATP) and potassium chloride (KCl)-induced contractions of the vas deferens in order to evaluate the effect of haloperidol, clozapine and aripiprazole on the contraction of the vas deferens.

METHODS

Male inbred BALB/c ByJ mice aged 7 weeks upon arrival to the laboratory were used in this study. Haloperidol, clozapine, aripiprazole, serotonin, noradrenaline, ATP and KCl were dissolved in 0.9% physiological saline. The mice were randomly divided into experimental groups as follows: saline; haloperidol 0.125 mg/kg; haloperidol 0.25 mg/kg; clozapine 1.25 mg/kg; clozapine 2.5 mg/kg; aripiprazole 3 mg/kg; aripiprazole 6 mg/kg. Mice were treated by ip injection of drugs during 21 days. Mice receiving only the vehicle ip (0.9% saline) during 21 days served as control group (n = 7). Each experimental group consisted of 7 mice. After 21 days of treatment, epididymal and prostatic portions of vas deferens were surgically dissected free and immersed in 20-mL organ baths containing Krebs' solution. The effects of chronic treatment with haloperidol (0.125 and 0.25 mg/kg), clozapine(1.25 and 2.5 mg/kg) and aripiprazole (3 and 6 mg/kg) were investigated on serotonin [10 (-8) to 10 (-4) M], noradrenaline [10 (-8) to 10 (-4) M], ATP [10 (-8) to 10 (-4) M] and 80 mM KCl-induced contractile responses in the epididymal and prostatic portions of mice isolated vas deferens strips. Statistical comparison between the groups was performed using ANOVA supported by Dunnett's post hoc test.

RESULTS

Serotonin-induced contractile responses were significantly increased in the epididymal and prostatic portions of the vas deferens obtained from the haloperidol-treated group and clozapine-treated group. However, aripiprazole treatment had no effect on serotonin responses in both epididymal and prostatic portions of mice vas deferens. On the other hand, haloperidol and clozapine treatments significantly inhibited both noradrenaline and ATP-induced contractions of the prostatic and epididymal portions of the mice vas deferens, but had no effect on KCl-induced contractions of the vas deferens in both portions. There were no significant differences in KCl-induced contractile responses among the groups.

CONCLUSIONS

These results revealed that induced contractions of vas deferens were affected after chronic treatment with haloperidol and clozapine but not aripiprazole. Serotonergic, noradrenergic and purinergic receptors may, at least in part, contribute to changes in vas deferens contractions in mice with chronic treatment of haloperidol and clozapine but not aripiprazole.

Role of Prefrontal Serotonergic and Dopaminergic Systems in Encounter-Induced Hyperactivity in Methamphetamine-Sensitized Mice

BACKGROUND

Isolation-reared mice show social encounter-induced hyperactivity with activation of prefrontal serotonergic and dopaminergic systems, but it is not known whether this stress response is observed in other pathological conditions. Here we examined whether the social encounter stimulation induces abnormal behavior during withdrawal in chronic methamphetamine-treated mice.

METHODS

To induce methamphetamine-induced behavioral sensitization, male mice were injected with methamphetamine (1 mg/kg) once daily for 7 days.

RESULTS

The encounter with an intruder elicited hyperactivity 24 h after the last injection of methamphetamine in methamphetamine-sensitized mice. This response was observed even as long as 2 weeks after withdrawal of methamphetamine. The encounter increased c-Fos expression in the prefrontal cortex, dorsal raphe nucleus and ventral tegmental area in methamphetamine-sensitized mice, while it did not in control mice. Furthermore, the encounter increased extracellular serotonin (5-HT) and dopamine, but not noradrenaline, levels in the prefrontal cortex in methamphetamine-sensitized mice. Local injection of 5,7-dihydroxytryptamine and 6-hydroxydopamine into the prefrontal cortex attenuated encounter-induced hyperactivity in methamphetamine-sensitized mice and it markedly decreased prefrontal 5-HT and dopamine levels, respectively. Pharmacological analysis showed that the encounter-induced hyperactivity is mediated by dopamine D1 receptors and 5-HT2A receptors and attenuated by anxiolytics and antidepressants such as diazepam, osemozotan and selective 5-HT reuptake inhibitors. The effect of paroxetine was blocked by the 5-HT3 receptor antagonist azasetron.

CONCLUSIONS

The present study shows that psychological stress elicits hyperactivity with activation of prefrontal 5-HT and dopamine systems in methamphetamine-dependent mice and suggests that the abnormal behavior is associated with anxiety and depression.

Potentials of Mangifera indica in the treatment of depressive-anxiety disorders: possible mechanisms of action

BACKGROUND

Mangifera indica (Anacardiaceae) is an important herb in the traditional African and Ayurvedic medicines. The stem barks are used in the treatment of hypertension, insomnia, tumour, depression, rheumatism and as a tonic. This study was carried out to investigate antidepressant- and anxiolytic-like effect of the hydroethanol stem bark extract of M. indica (HeMI) in mice.

METHODS

HeMI (12.5-100 mg/kg, p.o.) was administered 1 h before subjecting the animal to the forced swim test (FST), tail suspension test (TST) and elevated plus maze tests (EPM).

RESULTS

HeMI (12.5-100 mg/kg, p.o.) treatment produced significant reduction in immobility time [F(6.56)=8.35, p<0.001], [F(6,56)=7.55, p<0.001] in the FST and TST, respectively. Moreover, co-administration of sub-therapeutic doses of imipramine or fluoxetine with HeMI (3.125 mg/kg) elicited significant reduction in time spent immobile in the FST. However, pretreatment of mice with parachlorophenylalanine, metergoline, yohimbine or sulpiride abolished the antidepressant-like effect elicited by HeMI. In the EPM, HeMI produced significant [F(5,42)=8.91, p<0.001] increase in open arms exploration by 75.55 % and this effect was blocked by pretreatment of mice with flumazenil or metergoline.

CONCLUSIONS

Findings from this study showed antidepressant-like effect of M. indica through interaction with 5-HT2 receptor, α2-adrenoceptor and dopamine D2-receptors. Also, an anxiolytic-like effect through its affinity for 5-HT2 and benzodiazepine receptors. Hence, M. indica could be a potential phytotherapeutic agent in the treatment of mixed anxiety-depressive illness.

Elements toward novel therapeutic targeting of the adrenergic system

Adrenergic receptors belong to the family of the G protein coupled receptors that represent important targets in the modern pharmacotherapies. Studies on different physiological and pathophysiological properties of the adrenergic system have led to novel evidences and theories that suggest novel possible targeting of such system in a variety of pathologies and disorders, even beyond the classical known therapeutic possibilities. Herein, those advances have been illustrated with selected concepts and different examples. Furthermore, we illustrated the applications and the therapeutic implications that such findings and advances might have in the contexts of experimental pharmacology, therapeutics and clinic. We hope that the content of this work will guide researches devoted to the adrenergic aspects that combine neurosciences with pharmacology.

Antidepressant-like effect of the hydroethanolic leaf extract of Alchornea cordifolia (Schumach. & Thonn.) Mull. Arg. (Euphorbiaceae) in mice: involvement of monoaminergic system

ETHNOPHARMACOLOGICAL RELEVANCE

The leaf of Alchornea cordifolia (Euphorbiaceae) is used in traditional African medicine in the treatment of various neurological and psychiatric disorders including depression. Previous studies have shown its potent antidepressant-like effect in the forced swimming test (FST). Hence, this study sought to investigate the involvement of monoaminergic systems in the antidepressant-like effect elicited by hydroethanolic leaf extract of Alchornea cordifolia (HeAC) in the FST.

MATERIALS AND METHODS

HeAC (25-400mg/kg, p.o.) was administered 1h before the FST. To investigate the contribution of monoaminergic systems to antidepressant-like effect, receptors antagonists were injected 15min before oral administration of HeAC (200mg/kg) to mice and 1h thereafter, subjected to FST.

RESULTS

HeAC (200 and 400mg/kg, p.o.) produced dose dependent and significant (P<0.001) antidepressant-like effect, in the FST, without accompanying changes in spontaneous locomotor activities in the open-field test. The anti-immobility effect of HeAC (200mg/kg) in the FST was prevented by pretreatment of mice with SCH 23390 (0.05mg/kg, s.c., a dopamine D1 receptor antagonist), sulpiride (50mg/kg, i.p., a dopamine D2 receptor antagonist), prazosin (1mg/kg, i.p., an α1-adrenoceptor antagonist), yohimbine (1mg/kg, i.p., an α2-adrenoceptor antagonist), and GR 127993 (5-HT1B receptor antagonist). Similarly, 3 days intraperitoneal injection of p-chlorophenylalanine (pCPA, 150mg/kg, i.p., an inhibitor of serotonin synthesis) prevented the antidepressant-like effect elicited by HeAC. The combination of subeffective doses of imipramine (5mg/kg, p.o.) or fluoxetine (5mg/kg, p.o.), with HeAC (25mg/kg, p.o., subeffective dose) produced a synergistic antidepressant-like effect in the FST.

CONCLUSION

The hydroethanolic extract of Alchornea cordifolia possesses antidepressant-like effect mediated through interaction with dopamine (D1 and D2), noradrenergic (α1 and α2 adrenoceptors), and serotonergic (5HT1B receptors) systems. Also, the potentiation of the anti-immobility effect of conventional antidepressants (fluoxetine and imipramine) by Alchornea cordifolia suggest potential therapeutic effect in depression.

Evidence that the anxiolytic-like effects of the beta3 receptor agonist amibegron involve serotoninergic receptor activity

Anxiety disorders are the most common behavioral disorders, and they exhibit high comorbidity rates. The aim of the present study was to confirm the effects of Amibegron, the first selective beta 3 adrenergic agent, on anxiety and to demonstrate that different serotoninergic receptor subtypes are involved in this effect. We administered the serotonin 5-HT1A receptor antagonist WAY-100635, the serotonin 5-HT2A receptor antagonist Ketanserin and the serotonin 5-HT3 receptor antagonist Ondansetron in mice and evaluated their performance in the elevated plus-maze test. Mice administered with Amibegron (5 and 10 mg/kg) showed a dose-dependent prolonged time spent in the open arms and an increase in the number of entries into the open arms during the elevated plus-maze (EPM) test. However, in the control mice, administration of WAY, Ketanserin and Ondansetron demonstrated no effect on the time spent in the open arms and the number of entries into the open arms. In addition, these treatments all significantly reversed the effect of the Amibegron-induced (10 mg/kg) increase in the time spent in the open arms. However, only WAY and Ketanserin treatments reversed the Amibegron-induced increase in the number of entries into the open arms. In conclusion, Amibegron exerted a significant anxiolytic effect, which was as effective as Diazepam, in mice during the EPM test. This effect of Amibegron may be mediated by interactions with the serotonin 5-HT1A, 5-HT2A and 5-HT3 receptors.