Administration of memantine and imipramine alters mitochondrial respiratory chain and creatine kinase activities in rat brain.

Several studies have appointed for a role of glutamatergic system and/or mitochondrial function in major depression. In the present study, we evaluated the creatine kinase and mitochondrial respiratory chain activities after acute and chronic treatments with memantine (N-methyl-D: -aspartate receptor antagonist) and imipramine (tricyclic antidepressant) in rats. To this aim, rats were acutely or chronically treated for 14 days once a day with saline, memantine (5, 10 and 20 mg/kg) and imipramine (10, 20 and 30 mg/kg). After acute or chronic treatments, we evaluated mitochondrial respiratory chain complexes (I, II, II-III and IV) and creatine kinase activities in prefrontal cortex, hippocampus and striatum. Our results showed that both acute and chronic treatments with memantine or imipramine altered respiratory chain complexes and creatine kinase activities in rat brain; however, these alterations were different with relation to protocols (acute or chronic), complex, dose and brain area. Finally, these findings further support the hypothesis that the effects of imipramine and memantine could be involve mitochondrial function modulation.

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.

Evaluation of brain and kidney energy metabolism in an animal model of contrast-induced nephropathy.

Contrast-induced nephropathy is a common cause of acute renal failure in hospitalized patients, occurring from 24 to 48 h and up to 5 days after the administration of iodinated contrast media. Encephalopathy may accompany acute renal failure and presents with a complex of symptoms progressing from mild sensorial clouding to delirium and coma. The mechanisms responsible for neurological complications in patients with acute renal failure are still poorly known, but several studies suggest that mitochondrial dysfunction plays a crucial role in the pathogenesis of uremic encephalopathy. Thus, we measured mitochondrial respiratory chain complexes and creatine kinase activities in rat brain and kidney after administration of contrast media. Wistar rats were submitted to 6.0 ml/kg meglumine/sodium diatrizoate administration via the tail vein (acute renal failure induced by contrast media) and saline in an equal volume with the radiocontrast material (control group); 6 days after, the animals were killed and kidney and brain were obtained. The results showed that contrast media administration decreased complexes I and IV activities in cerebral cortex; in prefrontal cortex, complex I activity was inhibited. On the other hand, contrast media administration increased complexes I and II-III activities in hippocampus and striatum and complex IV activity in hippocampus. Moreover, that administration of contrast media also decreased creatine kinase activity in the cerebral cortex. The present findings suggest that the inhibition of mitochondrial respiratory chain complexes and creatine kinase caused by the acute renal failure induced by contrast media administration may be involved in the neurological complications reported in patients and might play a role in the pathogenesis of the encephalopathy caused by acute renal failure.

Treatment with olanzapine, fluoxetine and olanzapine/fluoxetine alters citrate synthase activity in rat brain.

A growing body of evidence has indicated that energy metabolism impairment may be involved in pathophysiology of some neuropsychiatric disorders. In this study, we evaluated the effect of acute and chronic administration of fluoxetine, olanzapine and the combination of fluoxetine/olanzapine on citrate synthase activity in brain of rats. For acute treatment, Wistar rats received one single injection of olanzapine (3 or 6mg/kg) and/or fluoxetine (12.5 or 25mg/kg). For chronic treatment, rats received daily injections of olanzapine (3 or 6mg/kg) and/or fluoxetine (12.5 or 25mg/kg) for 28 days. In the present study we observed that acute administration of olanzapine inhibited citrate synthase activity in cerebellum and prefrontal cortex. The acute administration of olanzapine increased citrate synthase activity in prefrontal cortex, hippocampus and striatum and fluoxetine increased citrate synthase activity in striatum. Olanzapine 3mg/kg and fluoxetine 12.5mg/kg in combination increased citrate synthase activity in prefrontal cortex, hippocampus and striatum. In the chronic treatment we did not observed any effect on citrate synthase activity. Our results showed that olanzapine and fluoxetine increased citrate synthase activity after acute, but not chronic treatment.

Tamoxifen effects on respiratory chain complexes and creatine kinase activities in an animal model of mania.

The present study aimed to investigate the effects of tamoxifen (TMX) on locomotor behavior and on the activities of mitochondrial respiratory chain complexes and creatine kinase (CK) in the brain of rats subjected to an animal model of mania induced by d-amphetamine (D-AMPH)-reversion and prevention protocols. The D-AMPH administration increased locomotor activity in saline-treated rats under prevention and reversion treatment; furthermore, there was evident reduction in the locomotion in the D-amphetamine group treated with TMX. D-AMPH significantly decreased the activity of mitochondrial respiratory chain complexes in saline-treated rats in prefrontal cortex, hippocampus, striatum and amygdala in both prevention and reversion treatment. Depending on the cerebral area and evaluated complex, TMX was able to prevent and reverse this impairment. A decrease in CK activity was also verified in the brain of rats when D-AMPH was administrated in both experiments; the administration of TMX reversed but not prevented the decrease in CK activity induced by D-AMPH. The present study demonstrated that TMX reversed and prevented the alterations in behavioral and energy metabolism induced by D-AMPH (alterations were also observed in bipolar disorder), reinforcing the need for more studies about inhibitors of PKC as possible targets for new medications in the treatment of bipolar disorder.

Inhibition of brain citrate synthase activity in an animal model of sepsis. / Inibição da atividade da citrato sintase cerebral em um modelo animal de sepse.

OBJECTIVE: An extensive body of evidence from experimental studies indicates that sepsis is associated with increased reactive oxygen species production, depletion of antioxidants, and accumulation of markers of oxidative stress. Moreover, mitochondrial dysfunction has been implicated in the pathogenesis of multiple organ dysfunction syndrome (MODS). Citrate synthase is an enzyme localized in the mitochondrial matrix and an important component of the Krebs cycle; consequently, citrate synthase has been used as a quantitative enzyme marker for the presence of intact mitochondria. Thus, we investigated citrate synthase activity in the brains of rats submitted to a cecal ligation puncture model of sepsis. METHODS: At several times points (3, 6, 12, 24 and 48 hours) after the cecal ligation puncture operation, six rats were killed by decapitation. Their brains were removed, and the hippocampus, striatum, cerebellum, cerebral cortex and prefrontal cortex were dissected and used to determine citrate synthase activity. RESULTS: We found that citrate synthase activity in the prefrontal cortex was inhibited 12, 24 and 48 hours after cecal ligation puncture. In the cerebral cortex, citrate synthase activity was inhibited 3, 12, 24 and 48 hours after cecal ligation puncture. Citrate synthase was not affected in the hippocampus, striatum or cerebellum up to 48 hours after cecal ligation puncture. CONCLUSION: Considering that energy impairment due to mitochondrial dysfunction in sepsis has been well described and that oxidative stress plays a crucial role in sepsis development, we believe that energy impairment may also be involved in these processes. If citrate synthase inhibition also occurs in a sepsis model, it is tempting to speculate that a reduction in brain metabolism may be related to the pathophysiology of this disease.

Evaluation of Krebs cycle enzymes in the brain of rats after chronic administration of antidepressants.

Several works report brain impairment of metabolism as a mechanism underlying depression. Citrate synthase and succinate dehydrogenase are enzymes localized within cells in the mitochondrial matrix and are important steps of Krebs cycle. In addition, citrate synthase has been used as a quantitative enzyme marker for the presence of intact mitochondria. Thus, we investigated citrate synthase and succinate dehydrogenase activities from rat brain after chronic administration of paroxetine, nortriptiline and venlafaxine. Adult male Wistar rats received daily injections of paroxetine (10mg/kg), nortriptiline (15mg/kg), venlafaxine (10mg/kg) or saline in 1.0mL/kg volume for 15 days. Twelve hours after the last administration, the rats were killed by decapitation, the hippocampus, striatum and prefrontal cortex were immediately removed, and activities of citrate synthase and succinate dehydrogenase were measured. We verified that chronic administration of paroxetine increased citrate synthase activity in the prefrontal cortex, hippocampus, striatum and cerebral cortex of adult rats; cerebellum was not affected. Chronic administration of nortriptiline and venlafaxine did not affect the enzyme activity in these brain areas. Succinate dehydrogenase activity was increased by chronic administration of paroxetine and nortriptiline in the prefrontal cortex, hippocampus, striatum and cerebral cortex of adult rats; cerebellum was not affected either. Chronic administration of venlafaxine increased succinate dehydrogenase activity in prefrontal cortex, but did not affect the enzyme activity in cerebellum, hippocampus, striatum and cerebral cortex. Considering that metabolism impairment is probably involved in the pathophysiology of depressive disorders, an increase in these enzymes by antidepressants may be an important mechanism of action of these drugs.

Brain creatine kinase activity is increased by chronic administration of paroxetine.

Major depression is a serious and recurrent disorder often manifested with symptoms at the psychological, behavioral, and physiological levels. In addition, several works also suggest brain metabolism impairment as a mechanism underlying depression. Creatine kinase (CK) plays a central role in the metabolism of high-energy consuming tissues such as brain, where it functions as an effective buffering system of cellular ATP levels. Considering that CK plays an important role in brain energy homeostasis and that some antidepressants may modulate energy metabolism, we decided to investigate CK activity from rat brain after chronic administration of paroxetine (selective serotonin reuptake inhibitor), nortriptiline (tricyclic antidepressant) and venlafaxine (selective serotonin-norepinephrine reuptake inhibitor). Adult male Wistar rats received daily injections of paroxetine (10 mg/kg), nortriptiline (15 mg/kg), venlafaxine (10 mg/kg) or saline in 1.0 mL/kg volume for 15 days. Twelve hours after the last administration, the rats were killed by decapitation, the hippocampus, striatum and prefrontal cortex were immediately removed, and activity of CK was measured. Our results demonstrated that chronic administration of paroxetine increased CK activity in the prefrontal cortex, hippocampus and striatum of adult rats. On the other hand, nortriptiline and venlafaxine chronic administration did not affect CK activity in these brain areas. In order to verify whether the effect of paroxetine on CK is direct or indirect, we also measured the in vitro effect of this drug on the activity of the enzyme. We verified that paroxetine did not affect CK activity in vitro. Considering that metabolism impairment is probably involved in the pathophysiology of depressive disorders, an increase in CK activity by antidepressants may be an important mechanism of action of these drugs.

Inibição da atividade da citrato sintase cerebral em um modelo animal de sepse / Inhibition of brain citrate synthase activity in an animal model of sepsis

OBJETIVO: Um amplo corpo de evidência oriundo de estudos experimentais indica que a sepse se associa com um aumento da produção de espécies de oxigênio reativo, depleção de antioxidantes, e acúmulo de marcadores de estresse oxidativo. Além disto, a disfunção mitocondrial foi implicada na patogênese da síndrome de disfunção de múltiplos órgãos. A citrato sintase é uma enzima que se localiza no interior das células, na matriz mitocondrial, sendo uma etapa importante do ciclo de Krebs; esta enzima foi utilizada como um marcador enzimático quantitativo da presença de mitocôndrias intactas. Assim, investigamos a atividade da citrato sintase no cérebro de ratos submetidos ao modelo sepse com de ligadura e punção do ceco. MÉTODOS: Em diferentes horários (3, 6, 12, 24 e 48 horas) após cirurgia de ligadura e punção do ceco, seis ratos foram sacrificados por decapitação, sendo seus cérebros removidos e dissecados o hipocampo, estriato, cerebelo, córtex cerebral e córtex pré-frontal, e utilizados para determinação da atividade de citrato sintase. RESULTADOS: Verificamos que a atividade de citrato sintase no córtex pré-frontal estava inibida após 12, 24 e 48 horas da ligadura e punção do ceco. No córtex cerebral, esta atividade estava inibida após 3, 12, 24 e 48 horas da ligadura e punção do ceco. Por outro lado a citrato sintase não foi afetada no hipocampo, estriato e cerebelo até 48 horas após a ligadura e punção do ceco. CONCLUSÃO: Considerando-se que é bem descrito o comprometimento da energia decorrente da disfunção mitocondrial na sepse, e que o estresse oxidativo desempenha um papel essencial no desenvolvimento da sepse, acreditamos que o comprometimento da energia pode também estar evolvido nestes processos. Se a inibição da citrato sintase também ocorre em um modelo de sepse, é tentador especular que a redução do metabolismo cerebral pode provavelmente estar relacionada com a fisiopatologia desta doença.

OBJECTIVE: An extensive body of evidence from experimental studies indicates that sepsis is associated with increased reactive oxygen species production, depletion of antioxidants, and accumulation of markers of oxidative stress. Moreover, mitochondrial dysfunction has been implicated in the pathogenesis of multiple organ dysfunction syndrome (MODS). Citrate synthase is an enzyme localized in the mitochondrial matrix and an important component of the Krebs cycle; consequently, citrate synthase has been used as a quantitative enzyme marker for the presence of intact mitochondria. Thus, we investigated citrate synthase activity in the brains of rats submitted to a cecal ligation puncture model of sepsis. METHODS: At several times points (3, 6, 12, 24 and 48 hours) after the cecal ligation puncture operation, six rats were killed by decapitation. Their brains were removed, and the hippocampus, striatum, cerebellum, cerebral cortex and prefrontal cortex were dissected and used to determine citrate synthase activity. RESULTS: We found that citrate synthase activity in the prefrontal cortex was inhibited 12, 24 and 48 hours after cecal ligation puncture. In the cerebral cortex, citrate synthase activity was inhibited 3, 12, 24 and 48 hours after cecal ligation puncture. Citrate synthase was not affected in the hippocampus, striatum or cerebellum up to 48 hours after cecal ligation puncture. CONCLUSION: Considering that energy impairment due to mitochondrial dysfunction in sepsis has been well described and that oxidative stress plays a crucial role in sepsis development, we believe that energy impairment may also be involved in these processes. If citrate synthase inhibition also occurs in a sepsis model, it is tempting to speculate that a reduction in brain metabolism may be related to the pathophysiology of this disease.