Role of neuronal nitric oxide synthase in hypoxia-induced anapyrexia in rats.

Anapyrexia (a regulated decrease in body temperature) is a response to hypoxia that occurs in organisms ranging from protozoans to mammals, but very little is known about the mechanisms involved. Recently, it has been shown that the NO pathway plays a major role in hypoxia-induced anapyrexia. However, very little is known about which of the three different nitric oxide synthase isoforms (neuronal, endothelial, or inducible) is involved. The present study was designed to test the hypothesis that neuronal nitric oxide synthase (nNOS) plays a role in hypoxia-induced anapyrexia. Body core temperature (T(c)) of awake, unrestrained rats was measured continuously using biotelemetry. Rats were submitted to hypoxia, 7-nitroindazole (7-NI; a selective nNOS inhibitor) injection, or both treatments together. Control animals received vehicle injections of the same volume. We observed a significant (P < 0.05) reduction in T(c) of approximately 2.8 degrees C after hypoxia (7% inspired O(2)), whereas intraperitoneal injection of 7-NI at 25 mg/kg caused no significant change in T(c). 7-NI at 30 mg/kg elicited a reduction in T(c) and was abandoned in further experiments. When the two treatments were combined (25 mg/kg of 7-NI and 7% inspired O(2)), we observed a significant attenuation of hypoxia-induced anapyrexia. The data indicate that nNOS plays a role in hypoxia-induced anapyrexia.     

Antidepressant-like deliverables from the sea: evidence on the efficacy of three different brown seaweeds via involvement of monoaminergic system

Brown seaweeds exhibit several health benefits in treating and managing wide array of ailments. In this study, the antidepressant-like effect of methaolic extracts from Sargassum swartzii (SS), Stoechospermum marginatum (SM), and Nizamuddinia zanardinii (NZ) was examined in forced swimming test (FST), in rats. Oral administration of SS, SM, and NZ extract (30–60 mg/kg) exhibited antidepressant-like activity in FST by reducing immobility time as compared to control group, without inducing significant change in ambulatory behavior in open field test. In order to evaluate the involvement of monoaminergic system, rats were pretreated with the inhibitor of brain serotonin stores p-chlorophenylalanin (PCPA), dopamine (SCH23390 and sulpiride), and adrenoceptor (prazosin and propranolol) antagonists. Rats receiving treatment for 28 days were decapitated and brains were analyzed for monoamine levels. It may be concluded that the extracts of SS, SM, and NZ produces antidepressant-like activity via modulation of brain monoaminergic system in a rat model.     

Antidepressant-like effect of onion (Allium cepa L.) powder in a rat behavioral model of depression

The present study evaluated the antidepressant-like effect of the quercetin-rich vegetable, onion, by using the rat behavioral model of depression, the forced swimming test (FST). Daily administration of onion powder at a dosage of 50 mg/kg of body weight/day for 14 days significantly reduced the immobility time in FST without changing the motor dysfunction, indicating that the daily consumption of onion exerted antidepressant-like activity. The plasma corticosterone level was elevated after an FST trial, and pretreatment with onion powder did not modulate this elevation. Although the FST trial tended to increase the dopaminergic activity in the rat hypothalamus, the administration of onion powder (50 mg/kg) suppressed the increase in the turnover of this neurotransmitter. However, the same prevention was also observed with a higher dosage of onion, in which no significant antidepressant effect was apparent. The results of the present study suggest that onion exerted antidepressant-like activity in a behavioral model that acted independently of the hypothalamic-pituitary-adrenal axis.     

Genistein regulated serotonergic activity in the hippocampus of ovariectomized rats under forced swimming stress

The mortality of individuals suffering from depression has been increasing, especially post-menopausal women; therefore, their care and treatment are important to maintain a high quality of life. In the present study, we evaluated the antidepressant-like effects of a major isoflavonoid, genistein (4',5,7-trihydroxyisoflavone), using a behavioral model of depression, the forced swimming test (FST), in ovariectomized rats. Daily administration of genistein to ovariectomized rats at a dosage of 10 mg/kg of body weight/d for 14 d significantly reduced the immobility time during the FST without changing motor dysfunction. On the other hand, a higher dosage, 100 mg/kg/d, did not have any effects on the immobility time compared with the vehicle control. Repeated administration of genistein at 10 mg/kg of body weight did not affect serotonergic activities in the hippocampus compared to the vehicle control in ovariectomized rats. A 5-min FST trial stimulated these activities. On the other hand, repeated pretreatment with genistein protected against changes in activity during the FST trial. These results suggest that daily consumption of genistein 10 mg/kg/d might have antidepressant-like effect on ovariectomized rats by regulating changes in serotonergic metabolism in the hippocampus under stressful conditions.     

Evaluation of Potential Antidepressant-Like Activity of Chalcone-1203 in Various Murine Experimental Depressant Models

Two classic animal behavior despair tests-the forced swimming test (FST) and the tail suspension test (TST) were used to evaluate antidepressant-like activity of a new chalcone compound, chalcone-1203 in mice. It was observed that chalcone-1203 at dose of 1, 5, and 10 mg/kg significantly reduced the immobility time in the FST and TST in mice 30 min after treatment. In addition, chalcone-1203 was found to exhibit significant oral activity in the FST in mice. It also produced a reduction in the ambulation in the open-field test in mice not previously habituated to the arena, but no effect in the locomotor activity in mice previously habituated to the open-field. The main monoamine neurotransmitters and their metabolites in mouse brain regions were also simultaneously determined by HPLC–ECD. It was found that chalcone-1203 significantly increased the concentrations of the main neurotransmitters 5-HT and NE in the hippocampus, hypothalamus and cortex. Chalcone-1203 also significantly reduced the ratio of 5-HIAA/5-HT in the hippocampus and cortex, shown down 5-HT metabolism compared with mice treated with stress vehicle. In conclusion, chalcone-1203 produced significant antidepressant-like activity, and the mechanism of action may be due to increased 5-HT and NE in the mouse hippocampus and cortex.     

The antidepressant-like effects of Aloysia polystachya (Griseb.) Moldenke (Verbenaceae) in mice

The aim of the present work is to evaluate the putative antidepressant-like effects of a hydro-ethanolic extract (CEAp) and their fractions from the aerial parts of Aloysia polystachya (Griseb.) Moldenke (Verbenaceae) on the performance of male mice in the forced swimming test (FST). A single dose (100.0 mg/kg p.o.) of CEAp, in male mice provoked a significant reduction of the immobility time (p<0.01). Such effect was also observed with short-term treatment (7 days) with single doses of 1.0 (p<0.01), 10.0 (p<0.05) and 100.0 (p<0.05) mg/kg/day of CEAp. Additionally, in a different set of experiments, repeated administration in a 24-h period (24, 18 and 1 h before swimming test) with doses of 1.0 (p<0.05) and 10.0 (p<0.05) mg/kg p.o., of CEAp and 10.0 mg/kg p.o., (p<0.05) of ethyl acetate fraction, provoked significant reduction of the immobility time of male mice in the FST. Moreover, it was noted important differences in the onset of the antidepressant-like effect in the FST, depending on the modality of treatment with CEAp (acute, short-term or repeated). Both, efficacy and potency were higher when repeated administration of CEAp was used, and surprisingly the dose of 10 mg/kg (24, 18 and 1 h before swimming test) was more effective than imipramine. In the same way, the short term administration (7 days) improved significantly efficacy and potency of the CEAp in comparison to a single dose treatment. The ethyl acetate fraction submitted to TLC demonstrated that main and minor components are phenolics and terpenes, respectively. In addition, this fraction gives a negative Shinoda's test for flavonoids. These results indicate an antidepressant-like profile of action for the hydro-ethanolic extract and the component(s) of the ethyl acetate fraction obtained from A. polystachya, which deserve further investigation.     

The involvement of NMDA and AMPA receptors in the mechanism of antidepressant-like action of zinc in the forced swim test

Antidepressant-like activity of zinc in the forced swim test (FST) was demonstrated previously. Enhancement of such activity by joint administration of zinc and antidepressants was also shown. However, mechanisms involved in this activity have not yet been established. The present study examined the involvement of the NMDA and AMPA receptors in zinc activity in the FST in mice and rats. Additionally, the influence of zinc on both glutamate and aspartate release in the rat brain was also determined. Zinc-induced antidepressant-like activity in the FST in both mice and rats was antagonized by N-methyl-d-aspartic acid (NMDA, 75 mg/kg, i.p.) administration. Moreover, low and ineffective doses of NMDA antagonists (CGP 37849, L-701,324, d-cycloserine, and MK-801) administered together with ineffective doses of zinc exhibit a significant reduction of immobility time in the FST. Additionally, we have demonstrated the reduction of immobility time by AMPA receptor potentiator, CX 614. The antidepressant-like activity of both CX 614 and zinc in the FST was abolished by NBQX (an antagonist of AMPA receptor, 10 mg/kg, i.p.), while the combined treatment of sub-effective doses of zinc and CX 614 significantly reduces the immobility time in the FST. The present study also demonstrated that zinc administration potentiated a veratridine-evoked glutamate and aspartate release in the rat’s prefrontal cortex and hippocampus. The present study further suggests the antidepressant properties of zinc and indicates the involvement of the NMDA and AMPA glutamatergic receptors in this activity.     

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.     

Hydroalcoholic Extract of Rabbiteye Blueberry (Vaccinium ashei) Leaves Mitigates Unpredictable Chronic Mild Stress Model Inducing Depressive-Like Behavior in Rats

Several studies reported that rabbiteye blueberry (Vaccinium ashei Reade) leaves present promising biological properties. To the best of our knowledge, no study investigated the possible application of their hydroalcoholic extract for treating mood disorders. Herein, we evaluated if the hydroalcoholic extract of rabbiteye blueberry (Vaccinium ashei Reade) leaves (HEV) promotes an antidepressant-like effect in rodents using chronic experimental approaches. The effect of repeated administration of HEV (50 mg/kg, p.o.) on the immobility time was assessed in the forced swimming test (FST) in an unpredictable chronic mild stress (UCMS) model. Repeated treatment with HEV reversed the depressive-like behavior induced by UCMS by reducing the immobility time. Besides, the exposure to HEV caused no changes in relative organ weights in rats submitted to UCMS. The results indicated that HEV administration presented antidepressant-like action devoid of toxic effects. Thus, it is possible to suggest its potential as a safe and accessible therapeutic tool in the management of depression and other related mood disorders.     

Possible involvement of nitric oxide (NO) signaling pathway in the antidepressant-like effect of MK-801(dizocilpine), a NMDA receptor antagonist in mouse forced swim test

L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) is an important signaling pathway involved in depression. With this information, the present study aimed to study the involvement of this signaling pathway in the antidepressant-like action of MK-801 (dizocilpine; N-methyl-d-aspartate receptor antagonist) in the mouse forced-swim test. Total immobility period was recorded in mouse forced swim test for 6 min. MK-801 (5-25 microg/kg., ip) produced a U-shaped curve in reducing the immobility period. The antidepressant-like effect of MK-801 (10 microg/kg, ip) was prevented by pretreatment with L-arginine (750 mg/kg, ip) [substrate for nitric oxide synthase (NOS)]. Pretreatment of mice with 7-nitroindazole (7-NI) (25 mg/kg, ip) [a specific neuronal nitric oxide synthase inhibitor] produced potentiation of the action of subeffective dose of MK-801 (5 microg/kg, ip). In addition, treatment of mice with methylene blue (10 mg/kg, ip) [direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase] potentiated the effect of MK-801 (5 microg/kg, ip) in the forced-swim test. Further, the reduction in the immobility period elicited by MK-801 (10 microg/kg, ip) was also inhibited by pretreatment with sildenafil (5 mg/kg, ip) [phosphodiesterase 5 inhibitor]. The various modulators used in the study and their combination did not produce any changes in locomotor activity per se and in combination with MK-801. MK-801 however, at higher doses (25 microg/kg, ip) produced hyperlocomotion. The results demonstrated the involvement of nitric oxide signaling pathway in the antidepressant-like effect of MK-801 in mouse forced-swim test.     

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.     

The antidepressant-like effect of inosine in the FST is associated with both adenosine A1 and A2A receptors

Inosine is an endogenous purine nucleoside, which is formed during the breakdown of adenosine. The adenosinergic system was already described as capable of modulating mood in preclinical models; we now explored the effects of inosine in two predictive models of depression: the forced swim test (FST) and tail suspension test (TST). Mice treated with inosine displayed higher anti-immobility in the FST (5 and 50 mg/kg, intraperitoneal route (i.p.)) and in the TST (1 and 10 mg/kg, i.p.) when compared to vehicle-treated groups. These antidepressant-like effects started 30 min and lasted for 2 h after intraperitoneal administration of inosine and were not accompanied by any changes in the ambulatory activity in the open-field test. Both adenosine A₁ and A_2A receptor antagonists prevented the antidepressant-like effect of inosine in the FST. In addition, the administration of an adenosine deaminase inhibitor (1 and 10 mg/kg, i.p.) also caused an antidepressant-like effect in the FST. These results indicate that inosine possesses an antidepressant-like effect in the FST and TST probably through the activation of adenosine A₁ and A_2A receptors, further reinforcing the potential of targeting the purinergic system to the management of mood disorders.     

In vitro and in vivo evidences that antioxidant action contributes to the neuroprotective effects of the neuronal nitric oxide synthase and monoamine oxidase-B inhibitor, 7-nitroindazole

The neuronal nitric oxide synthase (nNOS) inhibitor, 7-nitroindazole (7-NI) is neuroprotective against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism. Monoamine oxidase (MAO)-B inhibitory action partially contributes to this effect. We tested the hypothesis that 7-NI could be a powerful hydroxyl radical (OH) scavenger, and interferes with oxidative stress caused by MPTP. We measured OH, reduced glutathione (GSH), as well as superoxide dismutase (SOD) and catalase activities in the nucleus caudatus putamen and substantia nigra of Balb/c mice following MPTP and/or 7-NI administration. The nNOS inhibitor caused dose-dependent inhibition in the production of OH in (i) Fenton-like reaction employing ferrous citrate in a cell-free system in test tubes, (ii) in isolated mitochondrial preparation in presence of MPP+, and (iii) in the striatum of mice systemically treated with MPTP. An MPTP-induced depletion of GSH in both the nuclei was blocked by 7-NI, which was dose-dependent (10-50mg/kg), but independent of MAO-B inhibition. The nNOS-mediated recovery of GSH paralleled attenuation of MPTP-induced depletion of striatal dopamine. MPTP-induced increase in the activities of striatal or nigral SOD and catalase were significantly attenuated by 7-NI treatment. These results suggest potent antioxidant action of 7-NI in its neuroprotective effects against MPTP-induced neurotoxicity.     

The involvement of AMPA–ERK1/2–BDNF pathway in the mechanism of new antidepressant action of prokinetic meranzin hydrate

It was recently discovered that ketamine can relieve depression in a matter of hours through an action on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. This is much more rapid than the several weeks required for the available antidepressants to show therapeutic efficacy. However, ketamine has negative side effects. The aim of this study was to determine whether the natural prokinetic drug meranzin hydrate (MH) has a fast-acting antidepressant effect mediated by AMPA receptors. By means of in vivo and in vitro experiments, we found that (1) treatment of rats with MH at 9 mg/kg decreased immobility time in a forced swimming test (FST), as did the popular antidepressant fluoxetine and the AMPA receptor positive modulator aniracetam. Pretreatment of rats with NBQX (10 mg/kg), an antagonist of AMPA receptors, blocked this effect of MH. (2) MH increased number of crossings of forced swimming rats in the open field test. (3) FST enhanced hippocampal ERK1/2, p-ERK1/2 and BDNF expression levels. MH (9 mg/kg) treatment further up-regulated hippocampal p-ERK1/2 and BDNF expression levels, and this effect was prevented by NBQX. (4) MH-increased BDNF expression corresponded with MH-decreased immobility time in the FST. (5) In vitro experiments, we found that incubation of rats hippocampus slices with MH (10, 20 μM respectively) increased concentrations of BDNF and p-ERK1/2. This effect of MH (20 μM) were prevented by NBQX. In conclusion, in animals subjected to acute stress, the natural prokinetic drug MH produced a rapid effect mediated by AMPA receptors and involving BDNF modulation through the ERK1/2 pathway.     

TGF-beta1 and HGF coordinately facilitate collagen turnover in subepithelial mesenchyme

Administration of tacrine (5 mg/kg ip), an anticholinesterase agent, in rats pretreated (24 h beforehand) with lithium chloride (LiCl; 12 mEq/kg ip) provides a useful experimental model to study limbic seizures and delayed hippocampal damage. Here we report Western blotting evidence demonstrating that in rat LiCl and tacrine enhance the expression of neuronal nitric oxide synthase (nNOS), but not eNOS, enzyme protein in the hippocampus during the preconvulsive period and this triggers seizures and hippocampal damage. In fact, systemic administration of 7-nitro indazole (7-NI; 50 mg/kg given ip 30 min before tacrine), a selective inhibitor of nNOS, prevented the expression of motor and electrocortical (ECoG) seizures and abolished neuronal cell death in the hippocampus. A lower dose (5 mg/kg ip) of 7-NI was ineffective. In conclusion, the present data support a role for abnormal nNOS expression in the mechanism which triggers limbic seizures and delayed excitotoxic damage in the hippocampus of rat.     

Antidepressant-like activity of a Kampo (Japanese herbal) medicine, Koso-san (Xiang-Su-San), and its mode of action via the hypothalamic–pituitary–adrenal axis

Koso-san (Xiang-Su-San in Chinese), a Kampo (Japanese herbal) medicine, is used clinically in East Asia for the treatment of depression-like symptoms associated with the initial stage of the common cold, allergic urticaria due to food ingestion, irritable bowel syndrome, chronic fatigue syndrome, insomnia, and autonomic imbalance. However, the antidepressant-like activity of Koso-san has never been evaluated scientifically. In this study, ddY mice subjected to a combination of forced swimming and chronic mild stresses were termed depression-like model mice. The degree of the depression-like state was measured by the animal's duration of immobility using the forced swimming test (FST). Oral administration of Koso-san (1.0 g/kg/body wt./day, 9 days) significantly shortened the duration of immobility of the depression-like model mice in the FST; however, locomotor activity was not affected. Hyperactivity of the hypothalamic–pituitary–adrenal (HPA) axis plays an important role in the pathophysiology of depression. Levels of corticotropin-releasing hormone mRNA expression in the hypothalamus and proopiomelanocortin mRNA expression in the pituitary were significantly increased, and glucocorticoid receptor protein expression in the hypothalamus paraventricular nucleus was downregulated in the depression-like model mice. However, Koso-san ameliorated these alterations to the normal conditions.

The results of this study suggest that Koso-san shows the antidepressant-like effect through suppressing the hyperactivity of the HPA axis in depression-like model mice.     

Inhibition of neuronal nitric oxide synthase increases aggressive behavior in mice.

BACKGROUND: Mice with targeted disruption of the gene for the neuronal isoform of nitric oxide synthase (nNOS) display exaggerated aggression. Behavioral studies of mice with targeted gene deletions suffer from the criticism that the gene product is missing not only during the assessment period but also throughout development when critical processes, including activation of compensatory mechanisms, may be affected. To address this criticism, we have assessed aggressive behavior in mice treated with a specific pharmacological inhibitor of nNOS. MATERIALS AND METHODS: Aggressive behavior, as well as brain citrulline levels, were monitored in adult male mice after treatment with a specific nNOS inhibitor, 7-nitroindazole (7-NI) (50 mg/kg i.p.), which is known to reduce NOS activity in brain homogenates by > 90%. As controls, animals were treated with a related indazole, 3-indazolinone (3-I) (50 mg/kg i.p.) that does not affect nNOS or with on oil vehicle. RESULTS: Mice treated with 7-NI displayed substantially increased aggression as compared with oil- or 3-I-injected animals when tested in two different models of aggression. Drug treatment did not affect nonspecific locomotor activities or body temperature. Immunohistochemical staining for citrulline in the brain revealed a dramatic reduction in 7-NI-treated animals. CONCLUSIONS: 7-NI augmented aggression in WT mice to levels displayed by nNOS- mice, strongly implying that nNOS is a major mediator of aggression. NOS inhibitors may have therapeutic roles in inflammatory, cardiovascular, and neurologic diseases. The substantial aggressive behavior soon after administration of an nNOS inhibitor raises concerns about adverse behavioral sequelae of such pharmacological agents.     

Involvement of monoaminergic system in the antidepressant-like effect of the hydroalcoholic extract of Siphocampylus verticillatus

The antidepressant-like effect of the hydroalcoholic extract obtained from aerial parts of Siphocampylus verticillatus, a Brazilian medicinal plant, was investigated in two models of depression in mice and against synaptosomal uptake of serotonin, noradrenaline and dopamine. The immobility times in the forced swimming test (FST) and in the tail suspension test (TST) were significantly reduced by the extract (dose range 100-1000 mg/kg, i.p.), without accompanying changes in ambulation when assessed in an open-field. In addition when given orally the extract was also effective in reducing the immobility time in the TST. The efficacy of extract in the TST was comparable to that of the tricyclic antidepressant imipramine (15 mg/kg, i.p.) and with fluoxetine (32 mg/kg, i.p.). The anti-immobility effect of the extract (600 mg/kg, i.p.) assessed in the TST was not affected by pre-treatment with naloxone (1 mg/kg, i.p., a non-selective opioid receptor antagonist) or L-arginine (750 mg/kg, i.p., a nitric oxide precursor). In contrast, the extract (600 mg/kg, i.p.) antidepressant-like effect was significantly reduced by pre-treatment of animals with p-chlorophenylalanine (PCPA, 100 mg/kg, i.p., an inhibitor of serotonin synthesis), sulpiride (50 mg/kg, i.p., a selective D2 receptor antagonist), prazosin (62.5 microg/kg, i.p., an alpha1 adrenoreceptor antagonist) or by guanosine 5'-monophosphate (GMP, 250 mg/kg, i.p., a nucleotide known to block some actions elicited by NMDA). The biochemical data show that the extract of S. verticillatus inhibited in a graded manner the uptake of monoamines. However, at the IC50 level, the extract was approximately 3.2 to 3.4-fold more potent and also more efficacious in inhibiting the synaptosomal uptake of noradrenaline and serotonin than dopamine. Taken together these data demonstrate that the extract of S. verticillatus elicited a significant antidepressant-like effect, when assessed in the TST and FST in mice. Its action seems to involve an interaction with adrenergic, dopaminergic, glutamatergic and serotonergic systems.     

Evaluation of antidepressant-like activity of aqueous and ethanolic extracts of Terminalia bellirica Roxb. fruits in mice

The present study was undertaken to investigate the effect of aqueous and ethanolic extracts of T. bellirica on depression in mice using forced swim test (FST) and tail suspension test (TST). The extracts were administered orally for 10 successive days in separate groups of Swiss young male albino mice. Aqueous extract (50, 100 and 200 mg/kg) in a dose-dependent manner and ethanolic extract (100 mg/kg) significantly reduced the immobility time of mice in both FST and TST. The extracts were without any significant effect on locomotor activity of mice. The efficacies of aqueous extract (200 mg/kg) and ethanolic extract (100 mg/kg) were found to be similar to that of imipramine (15 mg/kg, po) and fluoxetine (20 mg/kg, po) administered for 10 successive days. Both extracts reversed reserpine-induced extension of immobility period of mice in FST and TST. Prazosin (62.5 microg/kg, ip; an alpha1-adrenoceptor antagonist), sulpiride (50 mg/kg, ip; a selective D2 receptor antagonist) and p-chlorophenylalanine (100 mg/kg, ip; an inhibitor of serotonin synthesis) significantly attenuated the aqueous and ethanolic extract-induced antidepressant-like effect in TST. Thus, both the aqueous and ethanolic extracts of T. bellirica elicited a significant antidepressant-like effect in mice by interaction with adrenergic, dopaminergic and serotonergic systems.