The involvement of glutamate in the pathophysiology of depression

In spite of more than 40 years of thorough studies, conventional antidepressants still have many limitations that hinder the effective treatment of depression. It seems that a breakthrough in the therapy of depression will require going beyond a monoamine-based theory of depression. Converging lines of evidence indicate that the glutamatergic system might be a promising target for a novel antidepressant therapy. Both ionotropic glutamate receptor ligands (functional NMDA receptor antagonists and AMPA receptor potentiators) and compounds acting at metabotropic glutamate receptors (mGluRs; group I mGluR antagonists, group II antagonists and group III agonists) produce antidepressant-like activity in several preclinical and some clinical studies. In this review, current knowledge and crucial hypotheses concerning the role of glutamate in the pathophysiology of depression are discussed.

Antidepressant-like effect of MPEP, a potent, selective and systemically active mGlu5 receptor antagonist in the olfactory bulbectomized rats

Using the olfactory bulbectomy model of depression, we examined the antidepressant-like activity of 2-methyl-6-(phenylethynyl)-pyridine (MPEP) in rats. Bulbectomized rats required a significantly greater number of trials to acquire the response similar to sham-operated controls in the passive avoidance model. Both the prolonged (but not acute) treatment with MPEP and with antidepressant drug-desipramine restored the learning deficit. The results indicate that the prolonged blockade of mGlu5 receptors exerts antidepressant-like effects in rats.

Antidepressant-like properties of zinc in rodent forced swim test

The effects of zinc, the N-methyl-D-aspartate glutamate receptor inhibitor, were studied in mice and rats using the forced swim test. Zinc (ZnSO4) in a dose of 30 mg/kg and imipramine (30 mg/kg), reduced the immobility time in the forced swim test in both species. Moreover, combined treatment in this test with zinc and imipramine at their ineffective doses (1 and 5 mg/kg, respectively) induced a statistically significant effect in rats. The doses active in the forced swim test reduced (in mice) or did not affect (in rats) locomotor activity. The results obtained indicate that zinc induces an antidepressant-like effect and enhances the effect of imipramine in the forced swim test, suggesting a potential antidepressant activity of zinc in humans.

The effect of prolonged imipramine and electroconvulsive shock treatment on calcium/calmodulin-dependent protein kinase II in the hippocampus of rat brain

The phosphorylation of substrate proteins by protein kinases plays a key role in signal transduction and function of neurons. Protein kinases have been associated with several physiological and pathological states including depression. The aim of the present study was to investigate the effect of imipramine and electroconvulsive treatment (ECS), both clinically effective treatments of depression, on the activity of calcium/calmodulin dependent protein kinase II (CaM-KII) in the hippocampus. Our results indicate that repeated (but not acute) imipramine and ECS administration significantly decreased CaM-KII activity by 65 and 70%, respectively, in the soluble fractions from hippocampus. This decreased enzyme activity was accompanied by a proportional decrease (60-70%) of the amount of a-CaM-KII in the same fraction. A single and repeated administration of imipramine produced a significant increase in the activity of CaM-KII (50 and 337%, respectively) in the particulate fraction from hippocampus. Similarly, a single and repeated ECS produced an increase in the enzyme activity by 22 and 240%, respectively. The amount of a-CaM-KII in the particulate fraction was not significantly affected by repeated antidepressant administration. It is postulated that changes in CaM-KII activity following chronic antidepressant treatment might represent and important step in expression of its antidepressive action.

Outbreak of ceftazidime-resistant Klebsiella pneumoniae in a pediatric hospital in Warsaw, Poland: clonal spread of the TEM-47 extended-spectrum beta-lactamase (ESBL)-producing strain and transfer of a plasmid carrying the SHV-5-like ESBL-encoding gene

In 1996 a large, 300-bed pediatric hospital in Warsaw, Poland, started a program of monitoring infections caused by extended-spectrum beta-lactamase (ESBL)-producing microorganisms. Over the first 3-month period eight Klebsiella pneumoniae isolates were identified as being resistant to ceftazidime. Six of these were found to produce the TEM-47 ESBL, which we first described in a K. pneumoniae strain recovered a year before in a pediatric hospital in Lódź, Poland, which is 140 km from Warsaw. Typing results revealed a very close relatedness among all these isolates, which suggested that the clonal outbreak in Warsaw was caused by a strain possibly imported from Lódź. The remaining two isolates expressed the SHV-5-like ESBL, which resulted from the horizontal transfer of a plasmid carrying the blaSHV gene between nonrelated strains. The data presented here exemplify the complexity of the epidemiological situation concerning ESBL producers typical for large Polish hospitals, in which no ESBL-monitoring programs were in place prior to 1995.

The sequence of 29.7 kb from the right arm of chromosome II reveals 13 complete open reading frames, of which ten correspond to new genes

We have determined the complete nucleotide sequence of a 29.7 kb segment from the right arm of chromosome II carried by the cosmid alpha 61. The sequence encodes the 3' region of the IRA1 gene and 13 complete open reading frames, of which ten correspond to new genes and three (CIF1, ATPsv and CKS1) have been sequenced previously. The density of protein coding sequences is particularly high and corresponds to 84% of the total length. Two new genes encode membrane proteins, one of which is particularly large, 273 kDa. In one case (ATPsv), the comparison of our sequence and the published sequence reveals significant differences.

Construction of cys:lac gene fusions in Escherichia coli and their use in the isolation of constitutive cysBc mutants

Operon fusions of the lacZ gene to two different genes of the cysteine regulon controlled by the cysB regulatory protein were isolated. The fusion strains were used for selection of cysB constitutive mutants. Three cysBc alleles have been characterized and cloned into multicopy plasmids.