The effects of carbamazepine on two animal models of depression

An Effective Phytoconstituent Aconitine: A Realistic Approach for the Treatment of Trigeminal Neuralgia

Trigeminal neuralgia pain remains a challenge to treat. Natural compounds may be promising options for relieving pain. This study was aimed at investigating the effects of aconitine in a rat model of trigeminal neuralgia pain. Infraorbital nerve chronic constriction injury was performed in adult Wistar Albino rats. After the neuropathic pain developed, the rats were assigned to one of the treatment groups: carbamazepine 40 or 80 mg/kg; aconitine 0.25, 0.50, or 0.75 mg/kg; or saline injection (control group). Behavioral testing with von Frey filaments and the rotarod test were carried out before the surgical procedure and on the 24th to 29th postoperative days. Following the completion of tests, ipsilateral and contralateral spinal cords were harvested for Western blot analyses to assess NR-1 protein expression. ANOVA followed by Mann-Whitney U test was performed for the statistical analyses. P values of <0.05 were considered significant. Aconitine significantly reduced mechanical sensitivity in a dose-dependent manner. A significant reduction in motor coordination was noted for the higher doses of aconitine which was similar with the 40 and 80 mg/kg doses of carbamazepine. NR-1 expression was reduced in the ipsilateral spinal cord, whereas no significant difference was noted between the groups in the expression of NR-1 in the contralateral spinal cord. Aconitine had a significant pain relieving effect, which was similar to carbamazepine, in a dose-dependent manner. Aconitine may be an alternative pharmacological agent for the control of trigeminal neuralgia pain.

Pharmacological evaluation of NO/cGMP/KATP channels pathway in the antidepressant-like effect of carbamazepine in mice

Carbamazepine, an anticonvulsant drug, has shown antidepressant effects in clinical and experimental models. Nitric oxide (NO) is a neurotransmitter in the central nervous system and has been involved in a variety of diseases including depression. In the present study, the involvement of NO/cyclic GMP/KATP channels pathway in the antidepressant action of carbamazepine was investigated in mice. The antidepressant-like activity was assessed in the forced swim test (FST) behavioral paradigm. Carbamazepine reduced (40 mg/kg, intraperitoneal) immobility period. The antidepressant-like effect of carbamazepine (40 mg/kg, intraperitoneal) was prevented by pretreatment with L-arginine [substrate for NO synthase (NOS), 750 mg/kg, intraperitoneal], sildenafil (a PDE-5 inhibitor, 5 mg/kg, intraperitoneal) and diazoxide (K+ channels opener, 10 mg/kg). Pretreatment of mice with L-NAME (a non-selective NOS inhibitor, 10 mg/kg, intraperitoneal), methylene blue (direct inhibitor of both NOS and soluble guanylate cyclase, 10 mg/kg, intraperitoneal) and glibenclamide (an ATP-sensitive K+ channel blocker, 1 mg/kg, intraperitoneal) produced potentiation of the action of a sub-effective dose of carbamazepine (30 mg/kg, intraperitoneal). Also, carbamazepine (30 mg/kg) potentiated the antidepressant-like effect of fluoxetine through NO modulation. The various modulators used in the study did not produce any changes in locomotor activity per se. The results demonstrated that the antidepressant-like effect of carbamazepine in the FST involved an interaction with the NO/cGMP/KATP channels pathway.

Chronic oral carbamazepine treatment elicits mood-stabilising effects in mice

OBJECTIVE

The underlying biology of bipolar disorder and the mechanisms by which effective medications induce their therapeutic effects are not clear. Appropriate use of animal models are essential to further understand biological mechanisms of disease and treatment, and further understanding the therapeutic mechanism of mood stabilisers requires that clinically relevant administration will be effective in animal models. The clinical regimens for mood-stabilising drugs include chronic oral administration; however, much of the work with animal models includes acute administration via injection. An effective chronic and oral administration of the prototypic mood stabiliser lithium was already established and the present study was designed to do the same for the mood stabiliser carbamazepine.

METHODS

Mice were treated for 3 weeks with carbamazepine in food. ICR mice were treated with 0.25%, 0.5% and 0.75%, and C57bl/6 mice with 0.5% and 0.75%, carbamazepine in food (w/w, namely, 2.5, 5.0 or 7.5 g/kg food). Mice were then tested for spontaneous activity, forced swim test (FST), tail suspension test (TST) and amphetamine-induced hyperactivity.

RESULTS

Oral carbamazepine administration resulted in dose-dependent blood levels reaching 3.65 μg/ml at the highest dose. In ICR mice, carbamazepine at the 0.5% dose had no effect on spontaneous activity, but significantly reduced immobility in the TST by 27% and amphetamine-induced hyperactivity by 28%. In C57bl/6 mice, carbamazepine at the 0.75% dose reduced immobility time in the FST by 26%.

CONCLUSIONS

These results demonstrate a behaviourally effective oral and chronic regimen for carbamazepine with mood stabilising-like activity in a standard model for mania-like behaviour and two standard models for depression-like behaviour.

Magnesium sulfate and sodium valproate block methylphenidate-induced hyperlocomotion, an animal model of mania

Magnesium sulfate (MgSO4) is used to treat and prevent eclamptic seizures, and several anticonvulsant drugs (e.g., sodium valproate) are clinically effective antimanic drugs. Psychostimulant-induced hyperlocomotion has been proposed as an animal model for the study of antimanic drugs. The present study evaluated the effects of MgSO4 and sodium valproate (as a positive control) on hyperlocomotion induced by methylphenidate in mice. Acute MgSO4 (300-400 mg/kg), but not sodium valproate (100-300 mg/kg), prevented the increase in locomotor activity induced by methylphenidate (5.0 mg/kg). In contrast, repeated treatment (14 days) with valproate (300 mg/kg), but not MgSO4 (400 mg/kg), blocked methylphenidate-induced hyperlocomotion. Thus, acute MgSO4 exerted antimanic-like effects in this animal model.

Allopregnanolone microinjected into the lateral septum or dorsal hippocampus reduces immobility in the forced swim test: participation of the GABAA receptor

Allopregnanolone is a 5α-reduced metabolite of progesterone with actions on γ-aminobutyric acid-A (GABAA) receptors that produce antidepressant-like effects. However, little is known about the target brain regions that mediate its antidepressant-like effects. In this study, allopregnanolone (2.0 μg/0.3 μl/rat) or its vehicle (35% cyclodextrin solution) were microinjected into the lateral septum, septofimbrial, or dorsal hippocampus of male Wistar rats that had previously received intraperitoneal injections of either saline or the GABAA antagonist bicuculline (1.0 mg/kg), and its effects were evaluated in the open field and forced swim tests. Allopregnanolone microinjected into the lateral septum or dorsal hippocampus, but not septofimbrial nucleus, induced a longer latency to the first immobility and a shorter total immobility time in the forced swim test compared with vehicle. Bicuculline pretreatment reversed the effect of allopregnanolone. None of the treatments produced significant changes in crossings in the open field test. In conclusion, allopregnanolone produces an antidepressant-like effect in rats submitted to the forced swim test through actions on GABAA receptors located in the lateral septum and dorsal hippocampus, which is consistent with the antistress effect of GABAA agonists in these particular brain structures.

Veratrine blocks the lamotrigine-induced swimming increase and immobility decrease in the modified forced swimming test

Lamotrigine exhibits an anti-immobility effect in the modified forced swimming test, increasing swimming and climbing, behaviors that are related to serotonergic and noradrenergic effects, respectively. However, these effects could be secondary to lamotrigine blockade of Na(+) sensitive channel. Thus, this study investigated the influence of veratrine (0.1 mg/kg, ip, 10 min before each lamotrigine administration), an Na(+) channel activator, in the effect of lamotrigine (20 mg/kg, ip, 24, 5, 1 h before the test session) in the modified forced swimming test. Veratrine pre-treatment blocked lamotrigine-induced immobility decrease and swimming increase but it did not change the effect of lamotrigine on climbing. These results suggest that the serotonergic effect of lamotrigine in the modified forced swimming test is dependent on Na(+) voltage sensitive channel blockade, whereas its noradrenergic effect is not.

Dual monoamine modulation for the antidepressant-like effect of lamotrigine in the modified forced swimming test

Lamotrigine is an anticonvulsant drug that exhibits a clinical antidepressant effect. However, few studies have been conducted with lamotrigine in animal models of depression and its mechanism of antidepressant action is still unclear. The present study evaluates the effect of lamotrigine (5-20mg/kg, i.p.) in the modified forced swimming test and compare its behavior pattern in the test with those of paroxetine (20mg/kg, i.p.), nortriptyline (20mg/kg, i.p.) and dizolcipine-MK-801 (0.1mg/kg, i.p.). The effect of lamotrigine on locomotor activity and memory was also studied in order to exclude false-positive results. At low doses, lamotrigine (10mg/kg) decreased immobility and increased climbing scores, a similar pattern to nortriptyline. A higher lamotrigine dose (20mg/kg) also increased swimming scores. Lamotrigine neither changed locomotion in the open-field test nor impaired habituation. Paroxetine and dizolcipine decreased immobility and increased swimming. Dizolcipine also decreased climbing. However, although the effects of paroxetine and nortriptyline were seen without effect on locomotor activity, dizolcipine increased locomotor activity. The present study indicates that the antidepressant-like effect of lamotrigine is probably related to noradrenergic/serotonergic systems.

The antidepressive-like effect of oxcarbazepine: possible role of dopaminergic neurotransmission

It has been previously shown that oxcarbazepine (OXCBZ), a keto-analogue of carbamazepine, exhibits an antidepressive-like effect profile in the learned helplessness and forced swimming test (FST). Since carbamazepine possesses dopaminergic effect, the present study was carried out to evaluate the extent to which the antidepressive effect of OXCBZ might be mediated by dopaminergic system. Thus, the effects of OXCBZ in haloperidol-induced catalepsy and apomorphine-induced stereotypy were studied. The anti-immobility effect of OXCBZ in the FST was also evaluated in haloperidol pre-treated rats. OXCBZ (40 and 80 mg/kg, i.p.) dose-dependently reduced the catalepsy induced by haloperidol (2.0 mg/kg, i.p.). Moreover, OXCBZ (80 mg/kg, but not 20 or 40 mg/kg, i.p.) increased the intensity of apomorphine-induced stereotypy (0.6 mg/kg, s.c.). Finally, it was observed that the combination of OXCBZ (80 mg/kg, i. p.) and haloperidol (0.5 mg/kg, i.p.) antagonized the anti-immobility effect of OXCBZ and further increased the immobility time when compared to haloperidol alone. Haloperidol alone (0.5 or 1. 0 mg/kg) did not change the immobility time. Thus, these results suggest that OXCBZ could enhance dopaminergic neurotransmission, which might mediate its antidepressive-like effect.

Decrease in erythrocyte:plasma lithium ratio by concurrent administration of psychotropic drugs and lithium in mice

1. Previous studies paying attention to concurrent use of lithium (Li+) with a neuroleptic were not done under constant and controlled conditions. We were therefore encouraged to do a prospectively controlled study, presuming constant relevant factors, on concomitant use of Li+ with neuroleptic as well as other psychotropic agents. 2. The effects of concurrent administration of chlorpromazine, haloperidol, imipramine and carbamazepine with Li+ on the erythrocyte:plasma Li+ ratio and the intraerythrocyte Li+ concentration were studied in mice by using a new, direct method of measuring erythrocyte Li+ concentration. 3. All of the foregoing agents with the exception of carbamazepine were observed to significantly decrease the Li+ ratio. 4. Lack of any significant effect by carbamazepine on Li+ transport may be an indication of this drug's efficacy as a supplement in Li+ therapy of bipolar affective disorders. 5. The decrease in Li+ ratio observed with chlorpromazine, haloperidol and imipramine may be explained through the mechanism by which these drugs stabilize the cell membrane and consequently affect Li+ transport in erythrocytes. 6. Moreover, our study proves that, although the Li(+)-sodium countertransport mechanism does not exist in mice, the same interaction between Li+ and other psychotropic drugs is seen. It can be concluded that such interaction is not mediated through Li(+)-sodium countertransport. 7. It is suggested that, with concurrent use of a psychotropic drug and Li+, the amount of intraerythrocyte Li+ concentration be measured, instead of relying on the plasma Li+ concentration alone.

The effect of oxcarbazepine on behavioural despair and learned helplessness

The effect of oxcarbazepine was evaluated in two tests of depression (forced swimming and learned helplessness) and in the open-field test. Acute (three times over 24 h) oxcarbazepine 80 mg/kg (but not 40 mg/kg) decreased immobility time in the forced swimming test. In the learned helplessness test, 4 days of treatment with oxcarbazepine 80 mg/kg reversed the deficits induced by foot-shock in rats submitted to the two-way active avoidance test. Oxcarbazepine 80 mg/kg did not modify the behaviour of rats in the open-field test, an indication that, at this dose, oxcarbazepine did not show a locomotor stimulatory effect. Thus, the data of the present study suggest that oxcarbazepine has a potential antidepressive effect.

Prolonged treatment with carbamazepine increases the stimulatory effects of ethanol in mice

Carbamazepine (CBZ) has been used in the treatment of alcohol withdrawal (AW). However, cases of induction of euphoric feelings when mixed with alcohol have been reported. We verified whether CBZ could potentiate ethanol stimulatory effects in animals. Two groups of mice were injected with saline (group I) or 2 g/kg ethanol (group II) IP, for 20 days. On the next day, each group was divided into two subgroups that received either a single dose of CBZ (10 mg/kg) or vehicle IP, followed, 30 min later, by saline or ethanol injection. Locomotor activity was measured. Acute CBZ did not change locomotor activity of ethanol-treated mice. Treatment with CBZ or vehicle continued for 6 days. Finally, on the 28th day, 30 min after the last CBZ or vehicle injection, an ethanol challenge was given to group II and a saline injection to group I. The results showed a significant potentiation of ethanol stimulatory effects by chronic CBZ treatment. Data indicated that CBZ should be cautiously administered to alcohol-dependent patients.

Depressive behavior and stress ulcer in Wistar Kyoto rats

Wistar Kyoto (WKY) rats, as compared to several other rat strains, are hypoactive in the open field test and in the defensive burying test. WKY rats readily acquire a learned helplessness task as well as a passive avoidance tasks. WKY rats also reveal a greater susceptibility to restraint-induced stress ulcer. The behavioral tests suggest the presence of depressive behavior in WKY rats. When exposed to the Porsolt forced-swim test of 'behavioral despair', WKY rats are judged as exhibiting more depressive behavior. Desipramine not only reduced immobility in the forced-swim test, but also diminished the severity of restraint-induced stress ulcer. These data suggested a heightened activity of the hypothalamic-pituitary axis. Basal plasma ACTH levels did not differ between WKY rats and Wistar rats, but serial plasma ACTH response to restraint stress was significantly greater for WKY rats. These data suggest that depressive behavior is a characteristic of WKY rats and this strain is a valuable model for studying depression which may be induced by an exaggerated stress response.

Effects of acute or chronic carbamazepine on experimentally-induced conflict in the rat

The effects of acutely or chronically administered carbamazepine were studied in rats submitted to the modified Geller-Seifter conflict test. Diazepam was used as a standard anxiolytic. The results showed an increase in punished response after carbamazepine, as observed with diazepam, leading to the suggestion of an anti-conflict-effect for this drug. No tolerance to the anti-punishment-effect was seen after chronic carbamazepine administration.

Stress ulcer susceptibility and depression in Wistar Kyoto (WKY) rats

In a series of studies, Wistar Kyoto (WKY) normotensive rats were more susceptible to water-restraint-induced stress ulcer as compared to spontaneously hypertensive rats (SHR) Fisher-344 (F344) and Wistar rats. In these same studies, WKY rats were also deficient in several behavioral tasks. The four strains were observed in the open-field test of emotionality and WKYs were judged more emotional. In a study on "learned helplessness" WKYs were more deficient in the acquisition of a shuttlebox escape response following unavoidable shock the day before. The prevalence of freezing behavior in the shuttlebox task and the low ambulation scores in the open-field test suggested depressive behavior as a WKY behavior characteristic. WKY rats were judged more depressed in the Porsolt forced-swim test as compared to the other strains. A possible depression-ulcer relationship may exist in WKY rats. This strain may represent a good model for studying possible relationships between depression and stress-induced disease.

"Behavioral despair" test predicts stress ulcer in WKY rats

Spontaneously hypertensive rats (SHR), Wistar Kyoto (WKY) and Wistar rats were exposed to Porsolt's forced-swimming test of "behavioral despair." In addition to floating time, which was the measure of despair, headshakes, bobbing, diving and struggling time were also recorded. Rats were subsequently exposed to the activity stress (A-S) ulcer procedure. Wistar rats had the highest struggling time scores and the fewest A-S ulcers. WKY rats were judged as more depressed and their ulcer severity scores were significantly greater as compared to SHR and Wistar rats. In addition, a within strains analysis revealed that WKY rats with high despair scores also had the most severe stress-ulcer scores. These data suggested that stress-ulcer disease may be more prevalent in animals which are prone to depression as defined by the Porsolt test. The value of WKY rats as an animal model to study the relationship between depression and stress ulcer is discussed.

Learned immobility explains the behavior of rats in the forced swimming test

The rat forced-swimming test (FST) is widely used for screening substances with a potential antidepressant effect. The rat immobility shown in the FST has been interpreted as "behavioral despair" and has been suggested as an animal model of human depression. In the following series of experiments it is shown that measuring rat mobility by an automatic recording device is more accurate than measuring immobility time by direct observation (Experiment 1 and 5). The automatic recording procedure was tested with imipramine and mianserin showing similar results to those reported in the literature using a direct observation procedure by the researcher (Experiment 2). In Experiment 3 it was demonstrated that: (a) rat mobility decreased with experience, (b) switching water depth on Day 2 of the test increased mobility and (c) anisomycin acts as a false positive. In Experiment 4 the possible state dependent effect of imipramine in the FST was studied. The effect of imipramine on rat behavior in the FST is not state dependent. The imipramine-saline group shows greater mobility than the saline-saline group and does not differentiate from the imipramine-imipramine group. Thus, it was suggested that imipramine could interfere with the acquisition and/or consolidation processes. In Experiment 5, it is shown that a single dose of 25 mg/kg of imipramine, administered before or immediately after training on Day 1, increases rat's mobility on Day 2, thus suggesting that imipramine alters the consolidation process. From these results it is suggested that the behavioral process involved in the FST is "learning to be immobile" instead of "behavioral despair" as previously suggested in the literature.