Ketamine plus imipramine treatment induces antidepressant-like behavior and increases CREB and BDNF protein levels and PKA and PKC phosphorylation in rat brain.

A growing body of evidence has pointed to the N-methyl-d-aspartate (NMDA) receptor antagonists as a potential therapeutic target for the treatment of major depression. The present study investigated the possibility of synergistic interactions between antidepressant imipramine with the uncompetitive NMDA receptor antagonist ketamine. Wistar rats were acutely treated with ketamine (5 and 10mg/kg) and imipramine (10 and 20mg/kg) and then subjected to forced swimming tests. The cAMP response element bindig (CREB) and brain-derived neurotrophic factor (BDNF) protein levels and protein kinase C (PKC) and protein kinase A (PKA) phosphorylation were assessed in the prefrontal cortex, hippocampus and amygdala by imunoblot. Imipramine at the dose of 10mg/kg and ketamine at the dose of 5mg/kg did not have effect on the immobility time; however, the effect of imipramine (10 and 20mg/kg) was enhanced by both doses of ketamine. Ketamine and imipramine alone or in combination at all doses tested did not modify locomotor activity. Combined treatment with ketamine and imipramine produced stronger increases of CREB and BDNF protein levels in the prefrontal cortex, hippocampus and amygdala, and PKA phosphorylation in the hippocampus and amygdala and PKC phosphorylation in prefrontal cortex. The results described indicate that co-administration of antidepressant imipramine with ketamine may induce a more pronounced antidepressant activity than treatment with each antidepressant alone. This finding may be of particular importance in the case of drug-resistant patients and could suggest a method of obtaining significant antidepressant actions whilst limiting side effects.

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.