Is it possible to predict the activity of a new antidepressant in animals with simple psychopharmacological tests?

Investigating the optimistic in-vitro and in-vivo therapeutic effects of wild grape: Vitis jacqumantii R. Parker

Vitis jacquemontii R. Parker is a wild grape traditionally used by indigenous people as a substitute for cultivated grapes. However, its therapeutic effects have not been extensively studied. In this study, we investigated the antioxidant, anticholinesterase, analgesic, and antidepressant properties of V. jacquemontii. The antioxidant potential of this wild fruit plant was evaluated using two widely recognized assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-asino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). In-vitro anticholinesterase effects were determined by assessing butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) inhibition. The analgesic activity was assessed through writhing and tail immersion test models, while the antidepressant effect was evaluated using forced swimming and tail suspension test models. Results revealed the exceptional potential of V. jacquemontii as a valuable natural resource. The fruit extract (VJF-Crd) demonstrated remarkable free radical scavenging abilities, with an impressive IC50 value of 34.96 μg/mL for DPPH and 56.48 μg/mL for ABTS. The leaf extract (VJL-Crd) also exhibited considerable antioxidant properties, with IC50 values of 73.68 μg/mL for DPPH and 86.72 μg/mL for ABTS. Furthermore, VJF-Crd and VJL-Crd extracts displayed potent inhibitory activity against cholinesterase enzymes, with VJF-Crd demonstrating strong inhibition and VJL-Crd showing moderate inhibition. In terms of analgesia, these extracts exhibited dose-dependent responses in various pain models, with significant protection against acetic acid-induced writhing and tail immersion, showcasing their potential as natural pain relievers. Moreover, both VJF-Crd and VJL-Crd extracts displayed a notable decrease in immobility in the forced swimming and tail suspension test models, indicating their potential as natural antidepressants. These findings underscore the untapped potential of V. jacquemontii as a source of valuable chemical constituents. The isolation and identification of phyto-constituents from this plant hold promise for new bioactive compounds, particularly in pain management. This study sheds light on the multifaceted medicinal attributes of V. jacquemontii and opens new avenues for developing natural remedies for different ailments, especially pain management.

Antidepressant-like effects of Cimicifuga dahurica (Turcz.) Maxim. via modulation of monoamine regulatory pathways

Sheng-ma is recorded in the Compendium of Materia Medica and mainly originates from the rhizomes of Cimicifuga dahurica (Turcz.) Maxim. (CD), Cimicifuga heracleifolia Kom. and Cimicifuga foetida L. The alcoholic extract of Cimicifuga foetida L. (Brand name: Ximingting®) has been approved for the treatment of perimenopausal symptoms accompanying hot flash, depression and anxiety in China. However, there's no further study about the antidepressant-like effects of C. dahurica (CD). The aim of this study is to investigate the antidepressant-like effect of CD extracted by 75% ethanol and its possible mechanisms.The neuro-protective effects of CD on injured PC12 cells induced by corticosterone was measured firstly. Then, forced swim test (FST), tail suspension test (TST), reserpine-induced hypothermia, 5-hydroxytryptophan (5-HTP) induced head twitch response in mice and chronic unpredictable mild stress (CUMS) on sucrose preference tests were executed. Moreover, the potential mechanisms were explored by measuring levels of monoamine neurotransmitter in mice frontal cortex and hippocampus, testing monoamine oxidase enzyme A (MAO-A) activities in the brains of CUMS-exposed mice. Results showed that CD (60, 120 mg/kg) can significantly decreased the immobility period in FST and TST in mice without affecting locomotor activity. CD (30 mg/kg, 60 mg/kg, 120 mg/kg) could significantly counteracted reserpine-induced hypothermia and increased the number of head-twitches in 5-HTP induced head twitch response. It was also found that the monoamine neurotransmitter levels in the hippocampus and frontal cortex were significantly increased in 60 mg/kg and 120 mg/kg CD treated mice. In addition, CD (60 and 120 mg/kg) significantly inhibited MAO-A after 6-week CUMS exposure. CD can effectively produce an antidepressant-like effect, which involved with modulation of monoamine regulatory pathways.

Preclinical reserpine models recapitulating motor and non-motor features of Parkinson’s disease: Roles of epigenetic upregulation of alpha-synuclein and autophagy impairment

Reserpine is an effective drug for the clinical treatment of hypertension. It also induces Parkinson’s disease (PD)-like symptoms in humans and animals possible through the inhibition of monoamine vesicular transporters, thus decreasing the levels of monoamine neurotransmitters in the brain. However, the precise mechanisms remain unclear. Herein, we aimed to develop a preclinical reserpine model recapitulating the non-motor and motor symptoms of PD and investigate the underlying potential cellular mechanisms. Incubation of reserpine induced apoptosis, led to the accumulation of intracellular reactive oxygen species (ROS), lowered DNA methylation of alpha-synuclein gene, resulted in alpha-synuclein protein deposition, and elevated the ratio of LC3-II/LC3-Ⅰ and p62 in cultured SH-SY5Y cells. Feeding reserpine dose-dependently shortened the lifespan and caused impairment of motor functions in male and female Drosophila. Moreover, long-term oral administration of reserpine led to multiple motor and non-motor symptoms, including constipation, pain hypersensitivity, olfactory impairment, and depression-like behaviors in mice. The mechanistic studies showed that chronic reserpine exposure caused hypomethylation of the alpha-synuclein gene and up-regulated its expression and elevated the ratio of LC3-II/LC3-Ⅰ and expression of p62 in the substantia nigra of mice. Thus, we established preclinical animal models using reserpine to recapitulate the motor and non-motor symptoms of PD. Chronic reserpine exposure epigenetically elevated the levels of alpha-synuclein expression possible by lowering the DNA methylation status and inducing autophagic impairment in vitro and in vivo.

Neoechinulins: Molecular, cellular, and functional attributes as promising therapeutics against cancer and other human diseases

Neoechinulins are fungal and plant-derived chemicals extracted from Microsporum sp., Eurotium rubrum, Aspergillus sp., etc. Two analogues of neoechinulin, i.e., A and B, exerted extensive pharmacological properties described in this review. Neoechinulin is an indole alkaloid and has a double bond between C8/C9, which tends to contribute to its cytoprotective nature. Neoechinulin A exhibits protection to PC12 cells against nitrosative stress via increasing NAD(P)H reserve capacity and decreasing cellular GSH levels. It also confers protection via rescuing PC12 cells from rotenone-induced stress by lowering LDH leakage. This compound has great positive potential against neurodegenerative diseases by inhibiting SIN-1 induced cell death in neuronal cells. Together with these, neoechinulin A tends to inhibit Aβ42-induced microglial activation and confers protection against neuroinflammation. Alongside, it also inhibits cervical cancer cells by caspase-dependent apoptosis and via upregulation of apoptosis inducing genes like Bax, it suppresses LPS-induced inflammation in RAW264.7 macrophages and acts as an antidepressant. Whereas, another analogue, Neoechinulin B tends to interfere with the cellular mechanism thereby, inhibiting the entry of influenza A virus and it targets Liver X receptor (LXR) and decreases the infection rate of Hepatitis C. The present review describes the pharmaceutical properties of neoechinulins with notes on their molecular, cellular, and functional basis and their therapeutic properties.

Neonatal Reserpine Administration Produces Widespread Neuronal Losses and ⍺-Synuclein Inclusions in a Rat Model

Historically, reserpine was widely used as an antihypertensive drug. However, severe motor and non-motor symptoms such as dyskinesia and depression led to the discontinuation of reserpine as a first-line treatment for hypertension. Reserpine functions by inhibiting vesicular monoamine transporter 2 (VMAT2), reducing sequestration of monoamines into synaptic vesicles. The consequent reduction in monoamines, most notably dopamine, serotonin and norepinephrine, in the central nervous system, causes well-defined symptoms such as catalepsy, hypoactivity and sedation in animals, and these motor and non-motor symptoms are well defined for reserpine treatment. However, no gross neuropathological changes in response to reserpine treatment have been reported previously in any animal model. In contrast, reducing VMAT2 expression in genetically modified VMAT2 LO mice leads to the production of ⍺-synuclein-positive aggregates and progressive nigrostriatal neuronal loss. These VMAT2 LO mice have reduced VMAT2 functionality during critical brain developmental stages and this could be the key to producing a reserpine model with matching histopathologies. The aim of this study was therefore to investigate the effect of neonatal reserpine administration on brain histology. We report here that a single dose of 5 mg kg^-1 reserpine administered subcutaneously to neonatal rats on postnatal day 3 leads to widespread neuronal loss in various brain regions including the substantia nigra pars compacta, ventral tegmental area, striatum, hippocampus, locus coeruleus, amygdala and cerebral cortex, and the presence of ⍺-synuclein-positive inclusions in the substantia nigra pars compacta and the dorsal striatum within 30 days of administration.

Myrsinoic acid B from Myrsine coriacea reverses depressive-like behavior and brain oxidative stress in streptozotocin-diabetic rats

AIMS

Major depressive disorder (MDD) affects approximately 322 million people worldwide and is a common comorbidity in patients with diabetes mellitus (DM). A possible pathophysiological mechanism correlating both diseases is the increased oxidative stress in brain regions due to hyperglycemia. Myrsine coriacea (Primulaceae) is popularly known as "capororoca" and studies have been shown that this plant exhibits several pharmacological properties attributed to myrsinoic acid A (MAA) and B (MAB). Indeed, previous results have been shown its effects on the central nervous system, leading us to explore possible psychotropic effects.

MAIN METHODS

The effects of treatment with hydroalcoholic extract of the barks from Myrsine coriacea (HEBMC, 150 mg/kg, o.g.), MAA (5 mg/kg, o.g.), and MAB (3 mg/kg, o.g.) were evaluated in streptozotocin (75 mg/kg, i.p.)-induced diabetic female rats. After 28 days of treatments, rats were submitted to the forced swim test (FST) and open field test (OFT). Also, superoxide dismutase (SOD) and catalase (CAT) activities, reduced glutathione (GSH) and lipid hydroperoxides (LOOH) levels were evaluated in the hippocampus (HIP) and prefrontal cortex (PFC) of these rats.

KEY FINDINGS

The treatment with MAA or MAB increased the latency of first immobility in diabetic rats, and the HEBMC administration decreased the immobility time, and increase the climbing in FST. However, only MAB treatment reduces the immobility time, increases the climbing, and swimming in FST, and increases the crossing of diabetic animals in the OFT. Besides, this behavioral improvement promoted by MAB administration was accompanied by reducing in oxidative stress in the HIP and PFC, but not reducing hyperglycemia in diabetic rats.

SIGNIFICANCE

The results suggest that MAB's antioxidant effect in the HIP of diabetic animals may be essential to its antidepressant-like effect.

Neuropharmacological characteristics of antidepressant action of a new 3-substituted thietane-1,1-dioxide derivative

Introduction: Due to severe burden of depressive disorders and a low rate of remission in patients receiving antidepressant therapy, there is an urgent need for developing novel agents with antidepressant action and a fundamentally new mechanism of action. 3-ethoxythietane-1,1-dioxide (N-199/1) is a new molecule that showed significant antidepressant properties when administered intraperitoneally once or repeatedly. The aim of the present study was to investigate the mechanism of action of N-199/1, using reserpine test.

Materials and methods: N-199/1 (2 mg/kg and 4.86 mg/kg) and the reference drugs (imipramine and fluoxetine) were administered once intraperitoneally to outbred male mice 4 h (Experiment 1) and 18 h (Experiment 2) after a single intraperitoneal injection of reserpine (2.5 mg/kg). The severity of reserpine-induced symptoms (hypothermia, ptosis and akinesia) was assessed.

Results and discussion: N-199/1 potentiated reserpine-induced hypothermia at both doses and reduced ptosis at a dose of 2 mg/kg when administered 4 h after reserpine. N-199/1 increased the duration of reserpine akinesia at a dose of 2 mg/kg when administered 18 h after reserpine and at a dose of 4.86 mg/kg when administered 4 h after reserpine. The effect of N-199/1 resembled the effect of fluoxetine and was dose-dependent.

Conclusion: Based on the results obtained, it can be assumed that the antidepressant action of N-199/1 is due to its serotonin-positive properties, and probably the blockade of serotonin 5HT2A/2C receptors and/or α2-adrenergic receptors. The effect of N-199/1 is dose-dependent and resembles the effect of fluoxetine.

Graphical abstract:

Anxiolytic- and antidepressant-like activities of hydroethanol leaf extract of Newbouldia laevis (P.Beauv.) Seem. (Bignoniaceae) in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Newbouldia laevis (Bignoniaceae) is a woody tropical plant commonly found in southwest Nigeria. Ethnobotanical survey and literature revealed its application in the management of CNS disorders e.g. psychosis, insomnia, convulsions and associated anxiety and depression. This study evaluated the anxiolytic and antidepressant activities of the hydroethanol leaf extract of N. laevis in mice.

MATERIALS AND METHODS

The hole-board (HBT), elevated plus maze (EPMT), light/dark exploration (LDET), open field (OFT), social interaction (SIT) (anxiolytic activity), forced swim (FST) and tail suspension (TST) (antidepressant property) tests were employed in this investigation. Mice randomly allotted to different groups were treated orally with distilled water (10 ml/kg), diazepam (1 and 3 mg/kg), imipramine (20 mg/kg) and N. laevis (25-200 mg/kg). The mice were subjected to the various tests 60 min post-treatment.

RESULTS

In the HBT, N. laevis (25 and 100 mg/kg) increased the number of sectional crossings significantly (p < 0.05). In the OFT, N. laevis (25-200 mg/kg) increased the number of general square crossings, centre square crossings, rearings and assisted rearings (p < 0.05). In the EPMT, the extract (25 and 50 mg/kg) increased the open arms time spent, number of head dips and entry (p < 0.05). In the LDET, N. laevis increased the number of transitions at 100 and 200 mg/kg (p < 0.05). For the SIT, N. laevis (25 and 200 mg/kg) increased the frequency and duration of interaction respectively (p < 0.05). In the FST and TST, N. laevis (25-200 mg/kg) increased the latency and reduced the total duration of immobility (p < 0.05). The effect of the extract on duration of immobility was significantly reversed by sulpiride (Dopamine D₂ receptor antagonist).

CONCLUSION

The hydroethanol leaf extract of N. laevis possesses anxiolytic- and antidepressant-like activities, the later possibly mediated by dopaminergic enhancement(s).

Potential antidepressant effect of amantadine: a review of preclinical studies and clinical trials

Objective:

Amantadine blocks N-methyl-D-aspartate (NMDA) receptors and has dopaminergic and noradrenergic action, a neurochemical profile that suggests its potential as an antidepressant drug. We conducted a systematic review of preclinical and clinical studies addressing the effects of amantadine in animal models of depression and in patients with depression.

Methods:

PubMed, Science Direct, and Web of Science were searched up to September 1, 2017 to identify clinical and preclinical studies. The following search terms were used: “amantadine AND depress*”; “amantadine AND mood”; “amantadine AND animal models AND antidepres*”; and “amantadine AND (forced swim, learned helplessness, reserpine, chronic mild stress, anhedonia, sucrose preference).”

Results:

Amantadine had antidepressant-like effects in animal models and appeared to potentiate the antidepressant effects of other antidepressants. These preclinical findings have received some support from the results of small open-label clinical trials, suggesting that amantadine can reduce depressive symptomatology and potentiate the antidepressant effects of monoaminergic drugs. In addition to its glutamatergic and dopaminergic effects, the potential antidepressant-like effects of amantadine have been linked to molecular and cellular actions, such as increased expression of neurotrophic factors (e.g., brain-derived neurotrophic factor), activation of σ₁ receptors, decreased corticosterone levels, and decreased inflammatory response to stress.

Conclusion:

Amantadine is an interesting candidate as new antidepressant drug for the treatment of depression.

Neoechinulin A induced memory improvements and antidepressant-like effects in mice

Neoechinulin A is an isoprenyl indole alkaloid that exhibits scavenging, neurotrophic factor-like, and anti-apoptotic activities. However, the effectiveness of neoechinulin A in animal models of disease has not yet been explored. In the present study, we investigated the effects of neoechinulin A on memory impairment in lipopolysaccharide (LPS)-treated mice and its antidepressant-like effects in mice. In the Y-maze test, the intracerebroventicular (i.c.v.) administration of LPS (10μg/mouse) significantly decreased spontaneous alternation behavior, which was prevented by the prior administration of neoechinulin A (300ng/mouse, i.c.v.). None of the treatments altered the locomotor activity of mice. Moreover, the administration of neoechinulin A decreased the immobility time in the forced-swim test or tail suspension test, which was prevented by the prior administration of WAY100635 (an antagonist of 5-HT1A receptors) and parachlorophenylalanine (an inhibitor of tryptophan hydroxylase). These results suggest that neoechinulin A improves memory functions in LPS-treated mice, and also exerts antidepressant-like effects through changes in the 5-HT system.

The antidepressant-like pharmacological profile of Yuanzhi-1, a novel serotonin, norepinephrine and dopamine reuptake inhibitor

Triple reuptake inhibitors that block dopamine transporters (DATs), norepinephrine transporters (NETs), and serotonin transporters (SERTs) are being developed as a new class of antidepressants that might have better efficacy and fewer side effects than traditional antidepressants. In this study, we performed in vitro binding and uptake assays as well as in vivo behavioural tests to assess the pharmacological properties and antidepressant-like efficacy of Yuanzhi-1. In vitro, Yuanzhi-1 had a high affinity for SERTs, NETs, and DATs prepared from rat brain tissue (Ki=3.95, 4.52 and 0.87nM, respectively) and recombinant cells (Ki=2.87, 6.86 and 1.03nM, respectively). Moreover, Yuanzhi-1 potently inhibited the uptake of serotonin (5-hydroxytryptamine; 5-HT), norepinephrine (NE) and dopamine (DA) into rat brain synaptosomes (Ki=2.12, 4.85 and 1.08nM, respectively) and recombinant cells (Ki=1.65, 5.32 and 0.68nM, respectively). In vivo, Yuanzhi-1 decreased immobility in a dose-dependent manner, which was shown among rats via the forced-swim test (FST) and mice via the tail-suspension test (TST). The results observed in the behavioural tests did not appear to result from the stimulation of locomotor activity. Repeated Yuanzhi-1 treatment (2.5, 5 or 10mg/kg) significantly reversed depression-like behaviours in chronically stressed rats, including reduced sucrose preference, decreased locomotor activity, and prolonged time to begin eating. Furthermore, in vivo microdialysis studies showed that 5- and 10-mg/kg administrations of Yuanzhi-1 significantly increased the extracellular concentrations of 5-HT, NE and DA in the frontal cortices of freely moving rats. Therefore, Yuanzhi-1 might represent a novel triple reuptake inhibitor and possess antidepressant-like activity.

Involvement of norepinephrine and serotonin system in antidepressant-like effects of hederagenin in the rat model of unpredictable chronic mild stress-induced depression

CONTEXT

Previous studies from our laboratory indicated that both acute and subchronic administration of Fructus Akebiae (FAE) [the fruit of Akebiae quinata (Thunb.) Decne, (Lardizabalaceae)] produce antidepressant-like effects in animal depressive behavior tests. FAE contains approximately 70% of hederagenin (HG) as its main chemical component.

OBJECTIVE

This study compared the antidepressant ability of FAE with that of HG in mice and further investigated the antidepressant-like effects and potential mechanisms of HG in rats subjected to unpredictable chronic mild stress (UCMS).

MATERIALS AND METHODS

Mice received FAE (50 mg/kg) and HG (20 mg/kg) once a day via intragastric administration (i.g.) for 3 weeks. The anxiolytic and antidepressant activities of FAE and HG were compared using elevated plus maze (EPM) and behavioral despair tests including tail suspension test (TST) and forced swimming test (FST), respectively. Antidepressant effects of HG (5 mg/kg) were assessed using the UCMS depressive rat model. Moreover, the levels of monoamine neurotransmitters and relevant gene expression in UCMS rats' hippocampi were determined through high-performance liquid chromatography with electrochemical detection and real-time polymerase chain reaction techniques.

RESULTS

The results of our preliminary screening test suggest that HG at 20 mg/kg, while not FAE at 50 mg/kg, significantly decreased the immobility in both TST and FST compared with the vehicle group when administered chronically; however, there were no significant differences observed between the HG and the FAE group. Chronic administration of HG failed to significantly reverse the altered crossing and rearing behavioral performance, time spent in the open arm and closed entries in the EPM, even if they showed an increased tendency, but HG significantly increased the percent of sucrose preference in the sucrose preference test (SPT) and decreased the immobility time in the FST. HG showed that significant increases of norepinephrine and serotonin levels and exhibited a tendency to increase the expression of 5-hydroxytryptamine (serotonin) 1A receptor mRNA, and to significantly decrease the expression of the mRNA for the serotonin transporter (5-HTT). However, there were no significant differences in the expression of the brain-derived neurotrophic factor.

CONCLUSION

These findings confirm the antidepressant-like effects of HG in a behavioral despair test and UCMS rat model, which may be associated with monoamine neurotransmitters and 5-HTT mRNA expression.

Antidepressant-like effect of novel 5-HT3 receptor antagonist N-n-butyl-3-ethoxyquinoxalin-2-carboxamide (6p): an approach using rodent behavioral antidepressant tests

Objective:

The present study was designed to investigate the antidepressant potential of N-n-butyl-3-ethoxyquinoxalin-2-carboxamide (6p), a novel 5-HT₃ receptor antagonist in rodent behavioral models of depression.

Materials and Methods:

The compound 6p was examined in various behavioral models like forced swim test (FST), tail suspension test (TST), mechanistic models [5-hydroxytryptophan (5-HTP)-induced head twitch and reserpine-induced hypothermia (RIH)], and in chronic surgery model-olfactory bulbectomy in rats.

Results:

Compound 6p (1, 2, and 4 mg/kg, i.p.) exhibited antidepressant-like effect in FST and TST after acute treatment without having an effect on baseline locomotor activity. Moreover, 6p (2 mg/kg, i.p.), potentiated the 5-HTP–induced head twitch responses in mice and inhibited the RIH in rats. Chronic treatment (14 days) with 6p (1 and 2 mg/kg, p.o.) and paroxetine (10 mg/kg, p.o.) in rats significantly reversed the behavioral anomalies induced by bilateral olfactory bulbectomy using open field exploration.

Conclusion:

The preliminary studies reveal that compound 6p exhibits antidepressant-like effect in behavioral rodent models of depression.

Antidepressant Potential of 5-HT3 Receptor Antagonist, N-n- propyl-3-ethoxyquinoxaline-2-carboxamide (6n)

The present study was designed to evaluate the antidepressant potential of 5-HT3 receptor antagonist N-n-propyl-3-ethoxyquinoxaline-2-carboxamide (6n). The compound ‘6n’ with optimum log P and pA₂ value identified from a series of compounds synthesized in our laboratory was subjected to forced Swim Test (FST) (1, 2, and 4 mg/kg, i.p) and Tail Suspension Test (TST) (1, 2, and 4 mg/kg, i.p.). The compound ‘6n’ significantly reduced the duration of immobility in mice without affecting the baseline locomotion. Moreover, ‘6n’ (2 mg/kg, i.p.) potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and ‘6n’ at tested dose (1 and 2 mg/kg, i.p.) reversed the reserpine-induced hypothermia in rats. In interaction studies of ‘6n’ with various standard drugs/ligands using FST, ‘6n’ (1 mg/kg, i.p.) potentiated the antidepressant effect of venlafaxine (4 and 8 mg/kg, i.p.) and fluoxetine (10 and 20 mg/kg, i.p.). Additionally, ‘6n’ (1 and 2 mg/kg, i.p.) influenced the effect of harmane (5 mg/ kg, i.p.) as well as reversed the effect of parthenolide (1 mg/kg, i.p.) by reducing the duration of immobility in FST. Furthermore, ‘6n’ (1 mg/kg, i.p.) potentiated the effect of bupropion (10 and 20 mg/kg, i.p.) in TST. Chronic ‘6n’ (1 and 2 mg/kg, i.p.) treatment attenuated the behavioral abnormalities in olfactory bulbectomized rats. In conclusion, these various findings reiterated the antidepressant-like effects of ‘6n’ in behavioral models of depression.

Antidepressant-like effects of methanol extract of Hibiscus tiliaceus flowers in mice

BACKGROUND

Hibiscus tiliaceus L. (Malvaceae) is used in postpartum disorders. Our purpose was to examine the antidepressant, anxiolytic and sedative actions of the methanol extract of H. tiliaceus flowers using animal models.

METHODS

Adult male Swiss albino mice were treated with saline, standard drugs or methanol extract of H. tiliaceus and then subjected to behavioral tests. The forced swimming and tail suspension tests were used as predictive animal models of antidepressant activity, where the time of immobility was considered. The animals were submitted to the elevated plus-maze and ketamine-induced sleeping time to assess anxiolytic and sedative activities, respectively.

RESULTS

Methanol extract of H. tiliaceus significantly decreased the duration of immobility in both animal models of antidepressant activity, forced swimming and tail suspension tests. This extract did not potentiate the effect of ketamine-induced hypnosis, as determined by the time to onset and duration of sleeping time.

CONCLUSION

Our results indicate an antidepressant-like profile of action for the extract of Hibiscus tiliaceus without sedative side effect.

Depressant-like effects of parthenolide in a rodent behavioural antidepressant test battery

The anti-serotonergic effects of parthenolide (PTL) demonstrated in platelets inspired the present psychopharmacological investigation, which employs a battery of rodent behavioural assays of depression. In mice, PTL (0.5-2 mg kg−1) exhibited dose-dependent depressant-like effects in a forced swim test and a tail suspension test, without affecting the baseline locomotor status. The doses (1 and 2 mg kg−1) that induced depressant-like effects were found to significantly reduce 5-hydroxytrypto-phan-induced head twitch response. Interaction studies revealed that the depressant-like effects of PTL (1 mg kg−1) were reversed more efficiently by serotonergic antidepressants (venlafaxine, escitalopram, citalopram, fluoxetine) than by others (desipramine, bupropion) tested. Chronic treatment of PTL (1 and 2 mg kg−1) augmented the hyper-emotionality of olfactory bulbectomized rats, when compared with sham rats, as observed in modified open field, elevated plus maze and social interaction paradigms. This study depicts the severe depressogenic potential of PTL (in its pure form) plausibly mediated by platelet/neuronal hypo-serotonergic effects.

Antidepressant-like effects of glucagon-like peptide-2 in mice occur via monoamine pathways

In this study, we investigated whether glucagon-like peptide-2 (GLP-2) had antidepressant-like effects in mice, and whether these activities were associated with monoamine systems in mice. Antidepressant-like effects were evaluated based on the immobility time in the forced-swim test. GLP-2 (1.5-6 microg/mouse, i.c.v.) significantly reduced the immobility time in a dose-dependent manner without affecting locomotor activity in the wheel running test and memory function in the step-down passive avoidance test. These effects were inhibited by pretreatment with metergoline (an antagonist of non-specific 5-HT receptors), parachlorophenylalanine (an inhibitor of 5-HT synthase), NAN-190 (an antagonist of 5-HT1A receptors), yohimbine hydrochloride (an antagonist of alpha2 adrenoceptors), atenolol (an antagonist of beta1 receptors), and raclopride (an antagonist of D2 receptors), but not prazosin (an antagonist of alpha1 adrenoceptors), ICI118551 (an antagonist of beta2 adrenoceptors), and SCH23394 (an antagonist of D1 receptors). These results suggest that GLP-2 exerts antidepressant-like effects in the forced-swim test in mice, which are associated with 5-HT1A, alpha2, beta1 and D2 receptors.

Hypericum grandifolium Choisy: a species native to Macaronesian Region with antidepressant effect

AIM OF THE STUDY

Various species of Hypericum genus have been used in the Canary Islands as sedative, diuretic, vermifuge, wound healing, antihysteric and antidepressant agent. Studies have shown that methanol extract of Hypericum grandifolium Choisy is active in tetrabenazine-induced ptosis and forced swimming tests. In the current study, the aqueous, butanol and chloroform fractions obtained from the methanol extract as well as three sub-fractions derived from the chloroform fraction were evaluated for their central nervous effects in mice, particularly their antidepressant activity.

MATERIALS AND METHODS

The central nervous effect of different fractions and sub-fractions of Hypericum grandifolium was evaluated in mice using various behavioural models including locomotor and muscle relaxant activity, forced swimming test, effect on normal body temperature, barbiturate-induced sleep, tetrabenazine-induced syndrome and 5-hydroxytryptohan-induced head twitches and syndrome.

RESULTS

We found that the butanol and chloroform fractions and all sub-fractions showed an antidepressant effect in the forced swimming test, the chloroform fraction being the most active. They produced no effects or only a slight depression of locomotor activity. Chloroform fraction significantly increased the pentobarbital-induced sleeping time, produced a slight but significant hypothermia and antagonized tetrabenazine-induced ptosis, whereas the butanol fraction produced a slight potentiation of 5-HTP-induced head twitches and syndrome.

CONCLUSIONS

The present results, together with previous pharmacological and phytochemical data, indicated that Hypericum grandifolium possess antidepressant-like effects in mice and that different constituents, such as the flavonoids and the benzophenone derivatives, could be responsible at least in part for the antidepressant effects observed for this species.

Genetic variation in cortico-amygdala serotonin function and risk for stress-related disease

The serotonin system is strongly implicated in the pathophysiology and therapeutic alleviation of stress-related disorders such as anxiety and depression. Serotonergic modulation of the acute response to stress and the adaptation to chronic stress is mediated by a myriad of molecules controlling serotonin neuron development (Pet-1), synthesis (tryptophan hydroxylase 1 and 2 isozymes), packaging (vesicular monoamine transporter 2), actions at presynaptic and postsynaptic receptors (5-HT1A, 5-HT1B, 5-HT2A, 5-HT2C, 5-HT3A, 5-HT4, 5-HT5A, 5-HT6, 5-HT7), reuptake (serotonin transporter), and degradation (monoamine oxidase A). A growing body of evidence from preclinical rodents models, and especially genetically modified mice and inbred mouse strains, has provided significant insight into how genetic variation in these molecules can affect the development and function of a key neural circuit between the dorsal raphe nucleus, medial prefrontal cortex and amygdala. By extension, such variation is hypothesized to have a major influence on individual differences in the stress response and risk for stress-related disease in humans. The current article provides an update on this rapidly evolving field of research.

Synthesis and antidepressant-like profile of novel 1-aryl-3-[(4-benzyl)piperidine-1-yl]propane derivatives

This study describes the chemical synthesis and pharmacological evaluation of some new 1-aryl-3-[(4-benzyl)piperidine-1-yl]propane derivatives as antidepressants. The structures attributed to the compounds were elucidated using IR and 1H-NMR spectroscopic techniques besides elemental analysis. The antidepressant-like effect of these compounds was assessed by using the forced swimming test (FST), a validated experimental model of depression in mice. A clear antidepressant-like effect was shown for compounds 1, 2 and 4 by a significant decrease in immobility behaviour.

Antidepressant-like effect of hyperfoliatin, a polyisoprenylated phloroglucinol derivative from Hypericum perfoliatum (Clusiaceae) is associated with an inhibition of neuronal monoamines uptake

This study investigated, in mice, the antidepressant like effect of hyperfoliatin, a prenylated phloroglucinol derivative isolated from the aerial parts of Hypericum perfoliatum, as well as its action on monoaminergic systems. In the forced-swimming test, hyperfoliatin dose-dependently reduced immobility time. Immobility was interpreted as an expression of "behavioural despair", which could be a component of depression syndrome. The effect of hyperfoliatin did not result from the stimulation of animal motor activity. Hyperfoliatin inhibited, in a concentration-dependent manner, the [(3)H]-dopamine, [(3)H]-serotonin and [(3)H]-noradrenaline synaptosomal uptakes, but did not prevent the binding of specific ligands to the monoamine transporters. These data suggest that the antidepressant-like effect of hyperfoliatin on the forced-swimming test is probably associated to monoamine uptake inhibition, due to a mechanism of action different from that of known antidepressants.

The endomorphin system and its evolving neurophysiological role

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two endogenous opioid peptides with high affinity and remarkable selectivity for the mu-opioid receptor. The neuroanatomical distribution of endomorphins reflects their potential endogenous role in many major physiological processes, which include perception of pain, responses related to stress, and complex functions such as reward, arousal, and vigilance, as well as autonomic, cognitive, neuroendocrine, and limbic homeostasis. In this review we discuss the biological effects of endomorphin-1 and endomorphin-2 in relation to their distribution in the central and peripheral nervous systems. We describe the relationship between these two mu-opioid receptor-selective peptides and endogenous neurohormones and neurotransmitters. We also evaluate the role of endomorphins from the physiological point of view and report selectively on the most important findings in their pharmacology.

Antidepressant activity of some Hypericum reflexum L. fil. extracts in the forced swimming test in mice

We previously reported that oral administration of the methanol extract obtained from the aerial part in blossom of Hypericum reflexum L. fil. was active in the tetrabenazine and forced swimming test. In the present study, the effect of the aqueous, butanol and chloroform fractions obtained from the methanol extract of this species on the central nervous system was investigated in mice, particularly in animal models of depression. Antidepressant activity was detected in the butanol and chloroform fractions of this species using the forced swimming test since both fractions induced a significant reduction of the immobility time, producing no effects or only a slight depression on spontaneous motor activity when assessed in a photocell activity meter. Moreover, these fractions did not alter significantly the pentobarbital-induced sleeping time. On the other hand, the chloroform fraction produced a slight but significant hypothermia and was also effective in antagonizing the ptosis induced by tetrabenazine. Furthermore, the butanol fraction produced a slight potentiation of the head twitches and syndrome induced by 5-HTP. Taken together, these data indicate that the butanol and chloroform fractions from Hypericum reflexum possess antidepressant-like effects in mice, providing further support for the traditional use of these plants in the Canary Islands folk medicine against central nervous disorders.

Antidepressant-like effect of endomorphin-1 and endomorphin-2 in mice

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2)) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) are two recently isolated mu-opioid selective peptides with a potent antinociceptive activity, involved in a number of physiological processes, including food intake, vasomotricity, sexual behavior, as well as neuroendocrine and cardiorespiratory functions. The neuroanatomical distribution of endomorphins prompted us to study their antidepressant activity in two animal behavioral models of depression: forced-swimming and tail-suspension tests. In both tests, the intracerebroventricular (i.c.v.) injection of either endomorphin-1 or endomorphin-2 significantly decreased the duration of immobility, interpreted as an expression of 'behavioral despair', which could be related to the depression syndrome. These effects of endomorphins did not result from the stimulation of the animal motor activity. We have also demonstrated that the antidepressant-like effect of endomorphins was antagonized by the universal opioid antagonist, naloxone and the mu-opioid receptor selective antagonist, beta-funaltrexamine. In contrast, this effect was not antagonized by delta- and kappa-opioid receptor selective antagonists, naltrindole and nor-binaltorphimine, respectively. The results of the present study demonstrate that endomorphin-1 and endomorphin-2 produce potent antidepressant-like effects after i.c.v. injection in mice. We may suggest that endomorphins and the mu-opioid receptors might be involved in the physiopathology of depressive disorders, and that the endomorphinergic system could serve as a novel target for the development of antidepressant drugs.

Antidepressant-like profile of action of two 4-amine derivatives of 10,11-dihydro-5H-dibenzo [a,d] cycloheptane in mice evaluated in the forced swimming test

This study investigated the antidepressant-like effect of 4-amine derivatives of 10,11-dihydro-5H-dibenzo-alkylamine-cycloheptane, 4-amine (3-N,N-dimethylpropylamine)-10,11-dihydro-5H-dibenzo[a,d]cycloheptane-5-one (ADDCH1) and 1,2,3,4,8,9-hexahydro-dibenzocyclohepta[4,4a,5-ef]1,4-diazepin (ADDCH2), in a validated experimental model of depression, the forced swimming test (FST) in mice. Female adult mice were sub-chronically (three doses in 24 h) or repeatedly (once a day for 10 days) treated with either of the compounds and evaluated in the FST. The sub-chronic treatment promoted a dose-dependent reduction in the immobility time in the FST with the doses of 50 mg/kg (ADDCH1) and 30 mg/kg (ADDCH2) ip being the most effective (33% and 37% of reduction, respectively). A similar profile of action was observed in the animals repeatedly treated with ADDCH1 50 mg/kg or ADDCH2 30 mg/kg ip (for 10 days) and there was no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. These findings suggest that these amine derivatives of the system dibenzocycloheptane have an antidepressant-like action which could be of clinical interest and, therefore, deserves further investigation. In addition, putative underlying mechanisms of action are discussed.

Hypericum caprifoliatum (Guttiferae) Cham. & Schltdl.: a species native to South Brazil with antidepressant-like activity

In this work, previously published and unpublished results on biological activity of Hypericum caprifoliatum, a native species to South Brazil, are presented. Lipophilic extracts obtained from this species showed an antidepressant-like activity in mice and rat forced swimming test. Results from in vivo experiments suggest an effect on the dopaminergic transmission. Besides that, in vitro experiments demonstrated that the extract and its main component (a phloroglucinol derivative) inhibit monoamine uptake in a concentration-dependent manner, more potently to dopamine, but this effect is not related to direct binding at the uptake sites. It was also observed that a 3-day treatment with lipophilic extract prevents stress-induced corticosterone rise in mice frontal cortex but not in plasma. The lipophilic and methanolic H. caprifoliatum extracts also demonstrated antinociceptive effect, which seems to be indirectly mediated by the opioid system. These results indicate that H. caprifoliatum presents a promising antidepressant-like effect in rodents which seems to be related to a mechanism different from that of other classes of antidepressants.

Antidepressant-like effect of saponins extracted from Chaihu-jia-longgu-muli-tang and its possible mechanism

In this study, we investigated the antidepressant-like effect of saponins (SCLM) extracted from a traditional Chinese medicine, Chaihu-jia-longgu-muli-tang (CLM), in mice and rats using the tail suspension test (TST) and forced swimming test (FST). Subchronic administration of 100 and 200 mg/kg (p.o.) SCLM for 7 days reduced immobility time in the TST and FST in mice and also decreased immobility time at 70 and 140 mg/kg (p.o.) in the FST in rats. The results also showed that the anti-immobility activity of SCLM in these two tests is dose-dependent, without accompanying significant effects on locomotor activity. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and lactic dehydrogenase (LDH) assays showed that 25, 50 and 100 microg/ml SCLM or 10 microM fluoxetine (FLU), protected PC12 cells from the lesion induced by 10 microM corticosterone (Cort) treatment for 48 h. In the fura-2/AM (acetoxymethyl ester) labeling assay, 50 and 100 microg/ml SCLM, 10 microM FLU attenuated the intracellular Ca2+ overloading induced by 200 microM Cort treatment for 48 h in PC12 cells. Using RT-PCR, the mRNA level of nerve growth factor (NGF) was also detected. Treatment with SCLM (50, 100 microg/ml) for 48 h elevated the NGF mRNA expression in PC12 cells. In summary, these results suggest that SCLM possesses an antidepressant-like activity in behavioral models that might be mediated via the cytoprotective action shown in PC12 cells.

The antidepressant-like effect of Hypericum caprifoliatum Cham & Schlecht (Guttiferae) on forced swimming test results from an inhibition of neuronal monoamine uptake

A crude (ECH) and a purified cyclohexane extract (HCP) of Hypericum caprifoliatum and their main phloroglucinol derivative (HC1) were evaluated regarding their action on monoaminergic systems, more precisely on dopamine. In rats and mice forced swimming test, ECH and HCP dose-dependently reduced the immobility time. The effect of the highest dose was prevented by a prior administration of either sulpiride or SCH 23390 (D(2) and D(1) dopamine receptor antagonist, respectively). HCP (360 mg/kg) decreased the locomotor activity of mice. ECH (90 mg/kg) caused hypothermia and potentiated apomorphine-induced (16 mg/kg) hypothermia in mice. HCP and HC1 inhibited, in a concentration-dependent and monophasic manner, the [(3)H]-DA, [(3)H]-NA and [(3)H]-5HT synaptosomal uptakes, but did not prevent the binding of specific ligands to the monoamine transporters. Moreover, when tested at the concentrations corresponding to its IC(50) on [(3)H]-DA uptake, HC1 did not induce a significant [(3)H]-DA release, while at a higher concentration (200 ng/ml) it enhanced significantly (by 12%) the synaptosomal DA release. These data suggest that the antidepressant-like effect of H. caprifoliatum on the forced swimming test is due to an increase in monoaminergic transmission, resulting from monoamine uptake inhibition, more potently of dopamine, which may be related to their phloroglucinol contents.

Affective responses to changes in day length in Siberian hamsters (Phodopus sungorus)

The goal of these experiments was to test the hypothesis that day length influences anxious- and depressive-like behaviors in reproductively photoperiodic rodents. Male and female Siberian hamsters (Phodopus sungorus) were exposed to long (16 h light/day; LD) or short (8 h light/day; SD) photoperiods beginning at the time of weaning (day 18). Two weeks later hamsters were subjected to a series of behavioral tests to quantify anxiety-and depressive-like behaviors. In an elevated plus maze, SD males exhibited longer latencies to enter an open arm, entered fewer open arms, and spent less time exploring open arms relative to LD hamsters. SD males were likewise slower to enter either of the distal arms of a completely enclosed T-maze, and in a hunger-motivated exploratory paradigm SD males were slower to enter an open arena for food as compared to LD males. In a forced-swimming model of behavioral despair, SD males exhibited immobility sooner, more often, and for a greater total amount of time relative to LD males. Total activity levels, aversiveness to light, olfactory function, and limb strength were unaffected by SD, suggesting that the behavioral changes consequent to SD are not attributable to sensory or motor deficits, but rather may arise from changes in general affective state. The anxiogenic and depressive effects of SD were largely absent in female hamsters. Together the results indicate that adaptation to short photoperiods is associated with increased expression of anxiety- and depressive-like behaviors relative to those observed under LD photoperiod conditions.

Antidepressant properties of some Hypericum canariense L. and Hypericum glandulosum Ait. extracts in the forced swimming test in mice

It has been shown in a previous work that the methanol extract obtained from the aerial part in blossom of Hypericum canariense L. and Hypericum glandulosum Ait. was active in the tetrabenazine and forced swimming test. In the present study, the central nervous effect of the aqueous, butanol and chloroform fractions obtained from the methanol extracts of these Hypericum species was investigated in mice, particularly in animal models of depression. It was found that the immobility time in the forced swimming test was significantly reduced by the butanol and chloroform fraction of both species assayed, producing no effects or only a slight depression on spontaneous motor activity when assessed in a photocell activity meter. In this regard, the efficacy of the chloroform extract from Hypericum glandulosum Ait. (500 mg/kg p.o.) in the forced swimming test was comparable to that of the tricyclic antidepressant imipramine (50 mg/kg p.o.). In addition, the Hypericum glandulosum chloroform fraction was also effective in antagonizing the ptosis induced by tetrabenazine. Moreover, Hypericum canariense butanol fraction and Hypericum glandulosum chloroform fraction produced a slight but significant hypothermia. Taken together, these data demonstrate that the butanol and chloroform fractions from Hypericum canariense and Hypericum glandulosum possess antidepressant-like effects in mice, providing further support for the traditional use of these plants in the Canary Islands folk medicine against central nervous disorders.

Behavioural characterisation of young adult transgenic mice overexpressing galanin under the PDGF-B promoter

The behavioural phenotype of transgenic mice (3- to 5-months old) overexpressing galanin (GalOE) under the platelet-derived growth factor B (PDGF-B) promoter was evaluated in a battery of tests, including open field, locomotor cages, light-dark exploration test, elevated plus-maze and the Porsolt forced swim test. Learning and memory were assessed in the passive avoidance and the Morris water maze tasks. No difference between genotypes was found in exploratory activity in the open field. GalOE mice showed a slight increase in spontaneous locomotor activity assessed in the locomotor cages, but the amphetamine-induced increase in locomotor activity was somewhat lower in GalOE mice. Anxiety-like behaviour in the three different tests including open field, light-dark exploration and elevated plus-maze did not differ between genotypes. In the Porsolt forced swim test, GalOE mice displayed an increased time of immobility, indicative of increased learned helplessness possibly reflecting increased stress-susceptibility and/or depression-like behaviour. GalOE mice showed normal learning and memory retention in the passive avoidance and the Morris water maze tasks. These data support the hypothesis that galanin may have a role in functions related to mood states including affective disorders.

Forced swimming test in mice: a review of antidepressant activity

RATIONALE

Among all animal models, the forced swimming test (FST) remains one of the most used tools for screening antidepressants.

OBJECTIVE

This paper reviews some of the main aspects of the FST in mice. Most of the sensitivity and variability factors that were assessed on the FST are summarized.

MECHANISMS

We have summarized data found in the literature of antidepressant effects on the FST in mice. From this data set, we have extrapolated information on baseline levels of strain, and sensitivity against antidepressants.

RESULTS

We have shown that many parameters have to be considered in this test to gain good reliability. Moreover, there was a fundamental inter-strain difference of response in the FST.

CONCLUSIONS

The FST is a good screening tool with good reliability and predictive validity. Strain is one of the most important parameters to consider. Swiss and NMRI mice can be used to discriminate the mechanisms of action of drugs. CD-1 seems to be the most useful strain for screening purposes, but this needs to be confirmed with some spontaneous locomotor activity studies.

Mutant mouse models of depression: Candidate genes and current mouse lines

Depression is a multifactorial and multigenetic disease. At present, three main theories try to conceptualize its molecular and biochemical mechanisms, namely the monoamine-, the hypothalamus-pituitary-adrenal- (HPA-) system- and the neurotrophin-hypotheses. One way to explore, validate or falsify these hypotheses is to alter the expression of genes that are involved in these systems and study their respective role in animal behavior and neuroendocrinological parameters. Following an introduction in which we briefly describe each hypothesis, we review here the different mouse lines generated to study the respective molecular pathways. Among the many mutant lines generated, only a few can be regarded as genetic depression models or as models of predisposition for a depressive syndrome after stress exposure. However, this is likely to reflect the human situation where depressive syndromes are complex, can vary to a great extent with respect to their symptomatology, and may be influenced by a variety of environmental factors. Mice with mutations of candidate genes showing depression-like features on behavioral or neurochemical levels may help to define a complex molecular framework underlying depressive syndromes. Because it is conceivable that manipulation of one single genetic function may be necessary but not sufficient to cause complex behavioral alterations, strategies for improving genetic modeling of depression-like syndromes in animals possibly require a simultaneous targeted dysregulation of several genes involved in the pathogenesis of depression. This approach would correspond to the new concept of 'endophenotypes' in human depression research trying to identify behavioral traits which are thought to be encoded by a limited set of genes.

Corticosteroid Receptor Transgenic Mice

Dysregulations and dysfunctions of corticosteroids and their receptors have been implicated in the pathogenesis of stress-related disorders, in particular in depression. It is currently under debate, however, whether corticosteroid imbalances are a cause or rather a consequence of affective disorders. Corticosteroids exert their effects mainly by two receptors: glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs). We present here analyses made on several strains of mice with targeted mutations of corticosteroid receptors. The results help to understand how corticosteroid receptors regulate the hypothalamic-pituitary-adrenal (HPA) system. Furthermore, first behavioral analyses have indicated that corticosteroid receptor mutant mice show alterations in their emotional behavior. Certain mouse strains with specific alterations of GR or MR expression may represent genetic models of depression or at least have a predisposition to develop a depressive or a depression-resistant state upon exposure to stress. The corticosteroid receptor-regulated target genes to be identified in these models may code for proteins that could represent new drug-targets for the treatment of affective disorders.

Amphetamine withdrawal does not produce a depressive-like state in rats as measured by three behavioral tests

Administration of amphetamine (AMPH) can induce symptoms of psychosis in humans and locomotor sensitization in rats; in contrast, withdrawal from a period of AMPH intake is most often associated with symptoms of human endogenous depression. The aim of this study was to determine whether AMPH withdrawal produces a depressive-like state in rats. The present study examined the effects of withdrawal from an escalating-dose AMPH schedule (ESC; three daily injections over 6 days, 1-5 mg/kg, i.p.) and an intermittent-dose AMPH schedule (INT; one daily injection over 6 days, 1.5 mg/kg, i.p.) on animals' performance in three behavioral paradigms related to depression: the Porsolt swim test, the learned helplessness assay and operant responding for sucrose on a progressive ratio schedule. ESC and INT AMPH withdrawal had no effect on any of these tests or on stress responsiveness as measured by increased plasma levels of corticosterone (CORT) and adrenocorticotropin following the swim test, although basal CORT levels were higher in AMPH-withdrawn animals compared to controls. Finally, we confirmed the presence of locomotor sensitization for both AMPH schedules after 30 days of withdrawal. Our results suggest that the ability of AMPH withdrawal to produce symptoms of depression may not be evident in all behavioral screens for depressive symptoms in the rat.

Neuropharmacological study of hetero[2,1]benzothiazepine derivatives analogues of tianeptine

Neuropharmacological studies were conducted in mice with a number of hetero[2,1]benzothiazepine derivatives, analogues of tianeptine. Seven of the 12 compounds under study potentiated the actions of 5-hydroxytryptophan (5-HTP, 50 mg/kg i.p.) and/or antagonised the hypothermia induced by high doses of apomorphine. Moreover, some of them inhibited the head twitches induced by 5-HTP (250 mg/kg i.p.) and the stereotyped behaviour and/or climbing behaviour of low doses of apomorphine. These compounds also produced a slight inhibition of exploratory behaviour in the holeboard test. On the other hand, no significant muscle relaxant, anticonvulsant and anxiolytic activities were observed at any dose employed. Together, these data suggest that some of the compounds under study exert antidepressant and neuroleptic effects in mice with no muscle relaxant, anxiolytic and anticonvulsant activities.

Evaluation of the central properties of several Hypericum species from the Canary Islands

The infusions of the aerial parts in blossom of Hypericum canariense, H. glandulosum, H. reflexum and H. grandifolium (Hypericaceae) were evaluated for their pharmacological activity on the central nervous system in mice using various behavioural models including locomotor and muscle relaxant activity, effect on normal body temperature, pentobarbital-induced sleep, oxotremorine and tetrabenazine-induced syndrome, apomorphine-induced hypothermia and 5-hydroxytryptophan-induced head twitches, as well as a forced swimming test. These infusions did not alter significantly the locomotor activity, pentobarbital induced sleeping time and body temperature, with the exception of H. canariense which produced a slight but significant hypothermia. Additionally, no muscle relaxant or anticholinergic activity were observed. These infusions antagonized the ptosis and/or motor depression induced by tetrabenazine as well as shortening the immobility time in the forced swimming test. The observations suggest that the infusions of these Hypericum species possess antidepressant activity in mice, without inducing muscle relaxation, anticholinergic and sedative properties.

Chronic inositol treatment reduces depression-like immobility of Flinders Sensitive Line rats in the forced swim test

Inositol, a precursor of the PIP cycle that was reported to have therapeutic effects in depressive patients and to be effective in two animal models of depression, was evaluated in the forced swim test using the genetic Flinders Sensitive Line (FSL) rats model of depression. Groups of rats were tested in a 2 x 2 design with Strain (FSL or Control) as one factor and Drug (Inositol or Placebo) as the second factor. Rats received chronic treatment (daily for 14 days) with inositol (1.2 g/kg) or placebo (1:2 glucose/mannitol solution). On day 14 rats were exposed to the forced swim test for 5 min and their behavior videotaped. Tapes were analyzed for three levels of activity: immobility, swimming, and vigorous struggle. Inositol countered the exaggerated immobility of FSL rats in the forced swim test, without affecting control animals. Data support our previous suggestion of inositol as a potential antidepressant.

Experimental conditions for the continuous subcutaneous infusion of four central analgesics in rats

For the analysis of pharmacotherapeutic regimens for chronic pain in animals, it is important to establish delivery methods in which analgesics can be administered continuously and at a constant rate for a prolonged period of time. This allows for the assessment of how drug effects may vary over time in the presence of ongoing pain. The present study determined, for four analgesic compounds, the maximal doses that met all of the following criteria: (i) water-soluble, (ii) stable over 14 days at 38 degrees C, and (iii) devoid of undesirable side-effects in normal rats, as assessed by evolution of body weight and temperature after the subcutaneous implantation of an osmotic mini-pump that continuously infused the compounds over a 14-day period. The results showed the maximal doses to be 5 mg/rat/day for morphine hydrochloride, 2.5 mg/rat/day for imipramine hydrochloride, 20 mg/rat/day for ketamine hydrochloride, and 10 mg/rat/day for gabapentin. These doses were further found to be sufficient to express each compound's representative pharmacological activity. The conditions identified here appear appropriate for future studies of these four compounds in rat models of chronic pain and neuropathic allodynia.

Antidepressant effects of the methanol extract of several Hypericum species from the Canary Islands

The aim of the present study was to investigate several neuropharmacological effects of the methanol extract of the aerial parts in blossom of Hypericum canariense, H. glandulosum, H. grandifolium and H. reflexum (Hypericaceae). These extracts did not alter significantly the locomotor activity, body temperature or the pentobarbital-induced sleeping time, with the exception of H. reflexum which significantly potentiated pentobarbital-induced sleeping time at both doses assayed (500 and 1000 mg/kg p.o.). Additionally, neither muscle relaxant nor anticholinergic activity was observed. These extracts antagonized the ptosis and/or motor depression induced by tetrabenazine and also shortened the immobility time in the forced swimming test. Moreover, the H. glandulosum and H. grandifolium extracts at 1000 mg/kg p.o. potentiated the head twitches induced by 5-HTP. These observations suggest that the methanol extract of the Hypericum species in doses of 500-1000 mg/kg p.o. possess antidepressant activity in mice, without inducing significant muscle relaxation, anticholinergic and sedative properties.