Effects of the Pulsed Electromagnetic Fields on Experimental Periodontitis and Estrogen Deficiency.

Periodontitis is an inflammatory disease resulting from a complex polymicrobial infection that causes tissue destruction in susceptible individuals. Osteoporosis has been associated with greater clinical attachment loss in patients with periodontitis. Experimental studies have shown positive results in the treatment of osteoporosis through pulsed electromagnetic field (PEMF) stimulation. The aim of this study was to evaluate the effects of PEMF in the presence of estrogen deficiency associated with periodontitis, verifying its role in bone metabolism and in the inflammatory response. Sixty rats were divided into four groups: Sham surgery + ligature-induced periodontitis (P); Sham surgery + ligature-induced periodontitis + PEMF therapy (P + PEMF); Ovariectomy surgery + ligature-induced periodontitis (P + OVX); Ovariectomy surgery + ligature-induced periodontitis + PEMF therapy (P + OVX + PEMF). The area of bone loss in the furcation region (BL), connective tissue attachment loss (CTAL) and alveolar bone loss (ABL), BV/TV and BMD were evaluated. In addition to immunohistochemical labelling of RANKL, OPG, and TRAP and the inflammatory response of interleukin (IL)-1b, IL-6, TNF-α, IL-10, and vascular endothelial growth factor. P + OVX showed significant BL in relation to P + PEMF and the greatest CTAL and ABL. P + OVX and P + OVX + PEMF showed a significant reduction in BV/TV (%). P and P + PEMF showed a significantly lesser amount of Tb.Sp (mm) while P + OVX and P + OVX + PEMF showed a lesser of Tb.N. P + PEMF had the greatest BMD. P + OVX presented higher RANKL and lower OPG immunolabeling than other groups. P + PEMF and P + OVX + PEMF showed a reduction on all biomarkers evaluated. The application of PEMF seems to attenuate the effects of bone loss in the presence of periodontitis and ovariectomy. © 2022 Bioelectromagnetics Society.

Imipramine induces hyperactivity in rats pretreated with ouabain: Implications to the mania switch induced by antidepressants.

BACKGROUND: Bipolar disorder (BD) is a psychiatric disorder with complex therapy, besides the treatment with antidepressants induce a mania switch. OBJECTIVE: Investigate the effect of the administration of imipramine (IMI) in rats submitted to intracerebroventricular (ICV) administrations of ouabain (OUA). METHODS: Adult Wistar rats (n = 28) were submitted to only one ICV administration of OUA or artificial cerebrospinal fluid. On the 7th and 9th days following the ICV administration, animals were submitted to a behavioral analysis comprising open field task and forced swimming test. Between the 9th and 14th days, the rats received one daily intraperitoneal administration of IMI or saline (Sal). On the 15th day rats were submitted to the last session of behavioral analysis, followed by euthanasia. The frontal cortex and hippocampus were dissected for the subsequent biochemical assessments: oxidative parameters, and Na+/K+-ATPase activity. RESULTS: OUA administration induced a manic-like effect on the 7th day and a depressive-like behavior on the 14th day. In contrast, IMI administration elicited significant mania switch-like effect on this same stage in animals who received OUA. OUA increased oxidative damage and activity of antioxidant enzymes in the brain of rats. IMI potentialized the oxidative damage of OUA. No significant differences between groups were observed in the Na+/K+-ATPase activity. CONCLUSION: The present study suggests that residual effects from inhibition of the Na+K+ATPase could be involved in the manic-switch observed in bipolar patients. Besides, the OUA model of bipolar disorder could be used to study bipolar disorder in the context of mania switch.

Coadministration of lithium and celecoxib attenuates the behavioral alterations and inflammatory processes induced by amphetamine in an animal model of mania.

The present study evaluated the effects of the coadministration of lithium (Li) and Cel on inflammatory parameters in an animal model of mania induced by dextroamphetamine (D-amph). It was used Wistar rats 60 days old (250-350 g). The animals (n = 10 per group) received D-amph (2 mg/kg) or saline solution of NaCl 0.9% (Sal) intraperitoneally once a day for 14 days. From day eight until 14, the animals from the D-amph and Sal groups received Li (24 mg/kg), Cel (20 mg/kg), Li + Cel or water via gavage. Behavioral analyses were performed using the open-field test. The levels of IL-1ß, IL-4, IL-10, and TNF-α were evaluated. The administration of D-amph induced hyperactivity in the rats, as well increased the IL-4, IL-10, and TNF-α levels in the serum, frontal cortex, and striatum of rats compared to those of the controls, and treatment with Li plus Cel reversed these alterations. In general, the administration of Li or Cel per se did not have effects on the behavioral and biochemical parameters. However, the treatment with Cel per se decreased only the IL-10 levels in the serum of animals. Besides, the treatment with Li or Cel decreased the IL-4 levels in the serum and reversed the effects of D-amph on this parameter in the frontal cortex. The treatment with Li reversed the effects of D-amph on the TNF-α levels in all tissues evaluated, and the administration of Cel reversed this alteration only in the striatum. It can be observed that treatment with Li plus Cel was more effective against damages caused by D-amph when compared to the administration of both treatments per se, suggesting that the coadministration can be more effective to treat BD rather than Li or Cel itself. The treatment with Li plus Cel was effective against the inflammation induced by D-amph.

Resveratrol protects the brain against oxidative damage in a dopaminergic animal model of mania.

The present study aimed to evaluate the effects of resveratrol on behavior and oxidative stress parameters in the brain of rats submitted to the animal model of mania induced by m-AMPH. In the first model (reversal treatment), rats received intraperitoneal (i.p.) injection of saline or m-AMPH (1 mg/kg body weight) once a day for 14 days, and from the 8th to the 14th day, they were orally treated with water or resveratrol (15 mg/kg), once a day. In the second model (maintenance treatment), rats were orally pretreated with water or resveratrol (15 mg/kg) once a day, and from the 8th to the 14th day, they received saline or m-AMPH i.p., once a day. Locomotor and exploratory activities were assessed in the open-field test. Oxidative and nitrosative damage parameters to lipid and proteins were evaluated by TBARS, 4-HNE, carbonyl, and 3-nitrotyrosine in the brain submitted to the experimental models. m-AMPH administration increased the locomotor and exploratory activities; resveratrol was not able to reverse or prevent these manic-like behaviors. Additionally, m-AMPH increased the lipid and protein oxidation and nitrosylation in the frontal cortex, hippocampus, and striatum of rats. However, resveratrol prevented and reversed the oxidative and nitrosative damage to proteins and lipids in all cerebral areas assessed. Since oxidative stress plays an important role in BD pathophysiology, supplementation of resveratrol in BD patients could be regarded as a possible adjunctive treatment with mood stabilizers.

The role of neurotrophic factors in manic-, anxious- and depressive-like behaviors induced by amphetamine sensitization: Implications to the animal model of bipolar disorder.

BACKGROUND: Bipolar disorder (BD) and substance use disorders share common symptoms, such as behavioral sensitization. Amphetamine-induced behavioral sensitization can serve as an animal model of BD. Neurotrophic factors have an important role in BD pathophysiology. This study evaluated the effects of amphetamine sensitization on behavior and neurotrophic factor levels in the brains of rats. METHODS: Wistar rats received daily intraperitoneal (i.p) injections of dextroamphetamine (d-AMPH) 2 mg/kg or saline for 14 days. After seven days of withdrawal, the animals were challenged with d-AMPH (0.5 mg/kg, i.p) and locomotor behavior was assessed. In a second protocol, rats were similarly treated with d-AMPH (2 mg/kg, i.p) for 14 days. After withdrawal, without d-AMPH challenge, depressive- and anxiety-like behaviors were evaluated through forced swimming test and elevated plus maze. Levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin 3 (NT-3), neurotrophin 4/5 (NT-4/5) and glial-derived neurotrophic factor (GDNF) were evaluated in the frontal cortex, hippocampus, and striatum. RESULTS: D-AMPH for 14 days augmented locomotor sensitization to a lower dose of d-AMPH (0.5 mg/kg) after the withdrawal. d-AMPH withdrawal induced depressive- and anxious-like behaviors. BDNF, NGF, and GDNF levels were decreased, while NT-3 and NT-4 levels were increased in brains after d-AMPH sensitization. LIMITATIONS: Although d-AMPH induces manic-like behavior, the mechanisms underlying these effects can also be related to phenotypes of drug abuse. CONCLUSIONS: Together, vulnerability to mania-like behavior following d-AMPH challenge and extensive neurotrophic alterations, suggest amphetamine-induced behavioral sensitization is a good model of BD pathophysiology.

Histone deacetylase activity and brain-derived neurotrophic factor (BDNF) levels in a pharmacological model of mania

Objective: In the present study, we aimed to examine the effects of repeated D-amphetamine (AMPH) exposure, a well-accepted animal model of acute mania in bipolar disorder (BD), and histone deacetylase (HDAC) inhibitors on locomotor behavior and HDAC activity in the prefrontal cortex (PFC) and peripheral blood mononuclear cells (PBMCs) of rats. Moreover, we aimed to assess brain-derived neurotrophic factor (BDNF) protein and mRNA levels in these samples. Methods: We treated adult male Wistar rats with 2 mg/kg AMPH or saline intraperitoneally for 14 days. Between the 8th and 14th days, rats also received 47.5 mg/kg lithium (Li), 200 mg/kg sodium valproate (VPT), 2 mg/kg sodium butyrate (SB), or saline. We evaluated locomotor activity in the open-field task and assessed HDAC activity in the PFC and PBMCs, and BDNF levels in the PFC and plasma. Results: AMPH significantly increased locomotor activity, which was reversed by all drugs. This hyperactivity was associated with increased HDAC activity in the PFC, which was partially reversed by Li, VPT, and SB. No differences were found in BDNF levels. Conclusion: Repeated AMPH administration increases HDAC activity in the PFC without altering BDNF levels. The partial reversal of HDAC increase by Li, VPT, and SB may account for their ability to reverse AMPH-induced hyperactivity. .

Histone deacetylase activity and brain-derived neurotrophic factor (BDNF) levels in a pharmacological model of mania.

OBJECTIVE: In the present study, we aimed to examine the effects of repeated D-amphetamine (AMPH) exposure, a well-accepted animal model of acute mania in bipolar disorder (BD), and histone deacetylase (HDAC) inhibitors on locomotor behavior and HDAC activity in the prefrontal cortex (PFC) and peripheral blood mononuclear cells (PBMCs) of rats. Moreover, we aimed to assess brain-derived neurotrophic factor (BDNF) protein and mRNA levels in these samples. METHODS: We treated adult male Wistar rats with 2 mg/kg AMPH or saline intraperitoneally for 14 days. Between the 8th and 14th days, rats also received 47.5 mg/kg lithium (Li), 200 mg/kg sodium valproate (VPT), 2 mg/kg sodium butyrate (SB), or saline. We evaluated locomotor activity in the open-field task and assessed HDAC activity in the PFC and PBMCs, and BDNF levels in the PFC and plasma. RESULTS: AMPH significantly increased locomotor activity, which was reversed by all drugs. This hyperactivity was associated with increased HDAC activity in the PFC, which was partially reversed by Li, VPT, and SB. No differences were found in BDNF levels. CONCLUSION: Repeated AMPH administration increases HDAC activity in the PFC without altering BDNF levels. The partial reversal of HDAC increase by Li, VPT, and SB may account for their ability to reverse AMPH-induced hyperactivity.

Effects of lithium and valproate on oxidative stress and behavioral changes induced by administration of m-AMPH.

In the last years our research group has studied and validated the animal model of mania induced by dextroamphetamine (d-AMPH). Considering the lack of animal models of mania reported in the literature; this study evaluated the possibilities to validate the animal model induced by methamphetamine (m-AMPH). Then, we evaluated the effects of lithium (Li), valproate (VPA) on the behavior and parameters of oxidative damage in rat brain after administration of m-AMPH. In the prevention treatment, Wistar rats were pretreated with Li, VPA or saline (Sal) for 14 days, and then, between days 8 and 14, rats were treated with m-AMPH (1, 0.5 or 0.25 mg/kg) or Sal. In the reversal treatment, rats were first given m-AMPH (0.25 mg/kg) or Sal. Locomotor behavior was assessed using the open-field task and parameters of oxidative damage were measured in brain structures. Our results show that the hyperactivity was prevented and reverted by Li and VPA only when m-AMPH was administered in the dose of 0.25mg/kg. In addition, the m-AMPH in all doses administrated induced oxidative damage in both structures tested in two models. Li and VPA reversed and prevented this impairment, however in a way dependent of cerebral area, the dose of m-AMPH and technique.

Differences between dextroamphetamine and methamphetamine: behavioral changes and oxidative damage in brain of Wistar rats.

In this study methamphetamine (m-AMPH) and dextroamphetamine (d-AMPH) were compared to determine the potency of the two drugs on behavior and oxidative damage in brain of rats. Male adult Wistar rats were given single (acute administration) or repeated (chronic administration, 14 days) intraperitoneal injections of saline (0.9% NaCl), d-AMPH (2 mg/kg) or m-AMPH (0.25, 0.5, 1 or 2 mg/kg). Locomotor activity was evaluated in open-field apparatus 2 h after the last drug injection. Additionally, thiobarbituric acid reactive substances (TBARS) and protein carbonyl formation were measured in the prefrontal cortex, amygdala, hippocampus and striatum. In both experiments, d-AMPH and m-AMPH (all doses administered) increased the locomotor activity of animals, meantime, no significant difference between d-AMPH and m-AMPH was observed. d-AMPH and m-AMPH increased lipid and protein damage, but m-AMPH was more potent than d-AMPH, however, this effect varies depending on the brain region and the experimental protocol. The results of this study show that d-AMPH and m-AMPH have similar behavioral effects, which previous studies had already reported. On the other hand, this study demonstrated that the m-AMPH induces oxidative damage greater than d-AMPH, showing neurochemical differences previously unknown.

Decreased BDNF levels in amygdala and hippocampus after intracerebroventricular administration of ouabain / Diminuição dos níveis de BDNF em amígdala e hipocampo após a administração intracerebroventricular de ouabaína

OBJECTIVE: The present study aims to investigate the effects of ouabain intracerebroventricular injection on BDNF levels in the amygdala and hippocampus of Wistar rats.METHODS: Animals received a single intracerebroventricular injection of ouabain (10-3 and 10-2 M) or artificial cerebrospinal fluid and immediately, 1h, 24h, or seven days after injection, BDNF levels were measured in the rat's amygdala and hippocampus by sandwich-ELISA (n = 8 animals per group).RESULTS: When evaluated immediately, 3h, or 24h after injection, ouabain in doses of 10-2 and 10-3 M does not alter BDNF levels in the amygdala and hippocampus. However, when evaluated seven days after injection, ouabain in 10-2 and 10-3 M, showed a significant reduction in BDNF levels in both brain regions evaluated.DISCUSSION: In conclusion, we propose that the ouabain decreased BDNF levels in the hippocampus and amygdala when assessed seven days after administration, supporting the Na/K ATPase hypothesis for bipolar illness.

OBJETIVO: O presente estudo tem como objetivo investigar os efeitos da injeção intracerebroventricular de ouabaína sobre os níveis de BDNF na amígdala e no hipocampo de ratos Wistar.MÉTODOS: Os animais receberam uma única injeção intracerebroventricular de ouabaína (10-3 and 10-2 M) ou fluido cerebroespinhal artificial e, imediatamente, 3h, 24h ou sete dias após a injeção, os níveis de BDNF foram mensurados na amígdala e hipocampo dos ratos por ELISA sandwich (n = 8 animais por grupo).RESULTADOS: Quando avaliados imediatamente após a injeção, 3h ou 24h, ouabaína nas doses 10-2 e 10-3 M não alterou os níveis de BDNF em ambas as estruturas avaliadas. Entretanto, quando avaliados sete dias após a injeção, ouabaína nas doses 10-2 e 10-3 M mostrou uma significante redução nos níveis de BDNF em amígdala e hipocampo.CONCLUSÃO: Em conclusão, propõe-se que a administração de ouabaína diminuiu os níveis de BDNF em amígdala e hipocampo quando avaliados sete dias após a injeção, suportando a hipótese da participação da Na/K ATPase no transtorno bipolar.

Behavioral and neurochemical effects of sodium butyrate in an animal model of mania.

The present study investigated the effect of the histone deacetylase inhibitor, sodium butyrate (SB), on locomotor behavior and on mitochondrial respiratory-chain complexes activity in the brain of rats subjected to an animal model of mania induced by d-amphetamine (d-AMPH). In the reversal treatment, Wistar rats were first treated with d-AMPH or saline (Sal) for 14 days. Thereafter, between days 8 and 14, rats were administered SB or Sal. In the prevention treatment, rats were treated with SB or Sal for 14 days and received d-AMPH or Sal between days 8 and 14. The d-AMPH treatment increased locomotor behavior in Sal-treated rats under reversion and prevention treatment, and SB reversed and prevented d-AMPH-related hyperactivity. Moreover, d-AMPH decreased the activity of mitochondrial respiratory-chain complexes in Sal-treated rats in the prefrontal cortex, hippocampus, striatum, and amygdala in both experiments, and SB was able to reverse and prevent this impairment. The present study suggests that the mechanism of action of SB involves induction of mitochondrial function in parallel with behavioral changes, reinforcing the need for more studies on histone deacetylase inhibitors as a possible target for new medications for bipolar disorder treatment.

Neuroanatomical profile of antimaniac effects of histone deacetylases inhibitors.

An increasing number of studies have evaluated the potential therapeutic relevance of histone deacetylases (HDAC) inhibitors in mood disorder including bipolar disorder (BD). It has been suggested that the anterior limbic, which controls impulsivity and psychosis, is dysfunctional in BD. The present studies aims to evaluate the effects of microinjection of HDAC inhibitors in the ventricle, amygdala, striatum, prefrontal, and hippocampus on m-amphetamine-induced manic-like behavior in rats. Rats were given a single intracerebral (in the ventricle, amygdala, striatum, prefrontal, or hippocampus) injection of artificial cerebrospinal fluid, sodium butyrate (SB), or valproate (VPA) followed by an intraperitoneal injection of saline or m-AMPH 2 h before the open-field task. The activity of HDAC was evaluated in amygdala, striatum, prefrontal, and hippocampus of animals. The microinjection of SB and VPA in the ventricle, amygdala, striatum, and prefrontal, but not in hippocampus blocked the hyperactivity induced by m-AMPH. In addition, SB and VPA inhibited the HDAC activity; however, this effect varied depending on the experimental procedure and the brain structure evaluated. Our results suggest that the antimanic effects of SB and VPA, HDAC inhibitors, are related to the amygdala, striatum, and prefrontal, but not the hippocampus. More studies are needed to clarify the therapeutic effects of the HDAC inhibitor in BD and thereby develop new drugs.

Lithium and valproate modulate antioxidant enzymes and prevent ouabain-induced oxidative damage in an animal model of mania.

In this study, we assessed the oxidative stress parameters in rats submitted to an animal model of mania induced by ouabain (OUA), which included the use of lithium (Li) and valproate (VPA). Li and VPA treatment reversed and prevented the OUA-induced damage in these structures, however, this effect varies depending on the brain region and treatment regimen. Moreover, the activity of the antioxidant enzymes, namely, superoxide dismutase (SOD) and catalase (CAT) was found to be increased and decreased, respectively, in the brain of OUA-administered rats. Li and VPA modulated SOD and CAT activities in OUA-subjected rats in both experimental models. Our results support the notion that Li and VPA exert antioxidant-like properties in the brain of rats submitted to animal model of mania induced by ouabain.

Effects of mood stabilizers on mitochondrial respiratory chain activity in brain of rats treated with d-amphetamine.

Bipolar disorder (BD) is a devastating major mental illness associated with high rates of suicide and work loss. There is an emerging body of data suggesting that bipolar disorder is associated with mitochondrial dysfunction. In this context, the present study aims to investigate the effects of mood stabilizers lithium (Li) and valproate (VPT) on mitochondrial respiratory chain activity in brain of rats undergoing treatment with the pro-manic agent d-AMPH d-amphetamine (d-AMPH). In the reversal treatment, Wistar rats were first given d-AMPH or saline for 14 days, and then, between days 8 and 14, rats were treated with Li, VPA or saline (Sal). In the prevention treatment, rats were pretreated with Li, VPA or Sal. Locomotor behavior was assessed using the open-field task and mitochondrial chain activity complexes I, II, III and IV were measured in brain structures (hippocampus, striatum and prefrontal). Li and VPA reversed and prevented d-AMPH-induced hyperactivity. In both experiments, d-AMPH inhibited mitochondrial respiratory chain activity in all analyzed structures. In the reversal treatment, VPA reversed d-AMPH-induced dysfunction in all brain regions analyzed. In the prevention experiment, the effects of Li and VPA on d-AMPH-induced mitochondrial dysfunction were dependent on the brain region analyzed. These findings suggested that dopamine can be an important link for the mitochondrial dysfunction seen in BD and, Li and VPA exert protective effects against this d-AMPH-induced mitochondrial dysfunction, but this effect varies depending on the brain region and the treatment regimen.

Intracerebroventricular ouabain administration induces oxidative stress in the rat brain.

Intracerebroventricular (ICV) injection of ouabain (a potent Na(+)/K(+)-ATPase inhibitor) in rats resulted in manic-like effects. There is an emerging body of data indicating that major neuropsychiatric disorders, such as bipolar disorder and schizophrenia, are associated with increased oxidative stress. In this study, we investigated the effects of ICV ouabain injection on oxidative stress parameters in total tissue of rat brain. Our findings demonstrated that ICV injection increased thiobarbituric acid reactive species levels and protein carbonyl generation in the prefrontal cortex and hippocampus of rats. Moreover, the activity of the antioxidants enzymes catalase and superoxide dismutase was altered in several areas of the rat brain and cerebrospinal fluid of ICV ouabain-subjected rats. These results showed that Na(+)/K(+)-ATPase inhibition can lead to oxidative stress in the brain of rats.

DNA damage after intracerebroventricular injection of ouabain in rats.

There is an emerging body of data suggesting that bipolar disorder is associated with DNA damage. Intracerebroventricular (i.c.v.) administration of ouabain in rats results in manic-like alterations. We evaluated DNA damage of peripheral blood, cerebrospinal fluid and hippocampus of rats after i.c.v. ouabain injection. Ouabain-induced hyperlocomotion was examined in an open field. Additionally, we used single cell gel electrophoresis (comet assay) to measure early transient damage in cerebrospinal fluid (CSF), hippocampus and blood; and the micronucleus test to measure persistent damage in total blood samples of rats after ouabain administration. Our findings demonstrated that ouabain induced hyperlocomotion in rats, and this response remained up to 7 days following a single i.c.v. injection. In addition, we observed that the persistent increase in the rat spontaneous locomotion is associated with increased hippocampal and peripheral index of early DNA damage in rats. No significant alterations were observed in the micronucleus frequency in total blood samples of the rats after the ouabain i.c.v. injection. These results suggest that ouabain may induce peripheral and central early DNA damage, but this early damage may be repaired.

Effects of mood stabilizers on hippocampus and amygdala BDNF levels in an animal model of mania induced by ouabain.

There is a body of evidence suggesting that BDNF is involved in bipolar disorder (BD) pathogenesis. Intracerebroventricular (ICV) injection of ouabain (OUA), a specific Na(+)/K(+) ATPase inhibitor, induces hyperlocomotion in rats, and has been used as an animal model of mania. The present study aims to investigate the effects of the lithium (Li) and valproate (VPT) in an animal model of mania induced by ouabain. In the reversal model, animals received a single ICV injection of OUA or cerebrospinal fluid (aCSF). From the day following the ICV injection, the rats were treated for 6 days with intraperitoneal (IP) injections of saline (SAL), Li or VPT twice a day. In the maintenance treatment (prevention model), the rats received IP injections of Li, VPT, or SAL twice a day for 12 days. In the 7th day of treatment the animals received a single ICV injection of either OUA or aCSF. After the ICV injection, the treatment with the mood stabilizers continued for more 6 days. Locomotor activity was measured using the open-field test and BDNF levels were measured in rat hippocampus and amygdala by sandwich-ELISA. Li and VPT reversed OUA-related hyperactive behavior in the open-field test in both experiments. OUA decreased BDNF levels in first and second experiments in hippocampus and amygdala and Li treatment, but not VPT reversed and prevented the impairment in BDNF expression after OUA administration in these cerebral areas. Our results suggest that the present model fulfills adequate face, construct and predictive validity as an animal model of mania.

Na+,K+-ATPase activity in an animal model of mania.

We evaluated Na(+),K(+)-ATPase activity in hippocampus of rats submitted to an animal model of mania which included the use of lithium and valproate. In the acute treatment, amphetamine or saline was administered to rats for 14 days, between day 8 and 14, rats were treated with lithium, valproate or saline. In the maintenance treatment, rats were treated with lithium, valproate or saline, between day 8 and 14, amphetamine or saline were administered. Locomotor activity was assessed by open field test and Na(+),K(+)-ATPase activity was measured. Our results showed that mood stabilizers reversed and prevented amphetamine-induced behavioral effects. Moreover, amphetamine (acute treatment) increased Na(+),K(+)-ATPase activity, and administration of lithium or valproate reversed this effect. In the maintenance treatment, amphetamine increased Na(+),K(+)-ATPase activity in saline-pretreated rats. Amphetamine administration in lithium- or valproate-pretreated animals did not alter Na(+),K(+)-ATPase activity. The findings suggest that amphetamine-induced hyperactivity may be associated with an increase in Na(+),K(+)-ATPase.