The effects of antidepressant drugs on kainate receptor mRNA levels

Genes involved in glucocorticoid receptor signalling affect susceptibility to mood disorders

OBJECTIVES

In mood disorders chronic stress contributes to decreased glucocorticoid receptor signalling in the brain and resistance in the periphery. We hypothesised that aberrant glucocorticoid receptor function may result from genetic predisposition and that decreased GR signalling in the brain correlates with the expression of genes regulating GR complex formation.

METHODS

We performed the association analysis of 698 patients: 490 patients with bipolar disorder and 208 patients with major depressive disorder and 564 control subjects. We genotyped 11 variants using TaqMan assays. Gene expression in the brain tissue was done in male Wistar rats after chronic mild stress protocol. The SRSF5 serum concentration was performed using ELISA. Data were analysed in Statistica and GraphPad.

RESULTS

We found an association of STIP1 and SRSF5 variants with major depressive disorder and BAG1 variant with bipolar disorder. Gene expression analysis in a rat model of depression confirmed significant changes in the expression of SRSF5, BAG1, and FKBP4 in the brain. For SRSF5, we observed significantly increased expression in the serum of depressed females and male rats exposed to chronic stress.

CONCLUSIONS

Our results indicate the involvement of genes associated with GR function, SRSF5, BAG1, and FKBP4 with susceptibility to mood disorders.

Lack of effect of antipsychotic and antidepressant drugs on glutamate receptor mRNA levels in rat brains

By employing multiprobe oligonucleotide solution hybridisation (MOSH) we have measured the levels of mRNA encoding the NMDA receptor subtypes (R1, R2A, R2B and R2C) and the non-NMDA glutamate receptor subtypes (GluR1, 2, 3, and 4) within rat brain following, 1-32 days of antipsychotic or antidepressant drug administration. The results suggest that the drugs studied do not significantly alter rat glutamatergic system mRNA levels when compared to controls.

Differential changes in glutamate receptor subunit messenger RNAs in rat brain after haloperidol treatment

Glutamate receptors are implicated in several neuropsychiatric disorders and in the actions of neuroleptic drugs used to treat them. To help clarify how these drugs impinge upon the glutamatergic system, we have studied the effects of 2 weeks' haloperidol (2 mg kg(-1) d(-1)) upon the distribution and abundance of glutamate receptor mRNAs in rat brain. The mRNAs detected were those encoding the glutamate-binding protein (GBP), the N-methyl D-aspartate (NMDA) receptor (NR1 subunit) and the flip and flop isoforms of α-amino-3-hydroxy- 5-methyl-4-isoxazolpropionate (AMPA)-preferring non-NMDA receptors gluR1 and gluR2. The mRNAs were studied using in situ hybridization histochemistry in dorsolateral striatum, nucleus accumbens, frontal cortex and hippocampus. Haloperidol led to an increase in GBP mRNA in striatum and frontal cortex but not in hippocampus. AMPA receptor mRNAs showed gene- and isoform-specific alterations in treated animals, with a significant increase in the proportion of gluR2 flip compared to gluR2 flop. The gluR1 flop:gluR2 flop ratio also increased. No differences were observed for NR1 mRNA in any area. Thus, subchronic administration of haloperidol has a molecularly and spatially specific effect upon expression of glutamate receptor-related transcripts. The data have several implications. Firstly, the enhanced expression of GBP mRNA may contribute to the alterations in other glutamatergic parameters observed after neuroleptics. Secondly, the pattern of changes for the NMDA and AMPA receptor mRNAs suggests that the alterations in density of these receptors and their mRNAs reported in schizophrenia are not an artefact of neuroleptic treatment. Finally, the specific increase in flip:flop mRNA ratio for gluR2, together with the increased proportion of gluR1 flop:gluR2 flop mRNA, is likely to affect the properties of the encoded AMPA receptors. Such changes may be relevant to the desired or undesired effects of these drugs.

Effects of the serotonin reuptake inhibitor fluvoxamine on yohimbine-induced anxiety in panic disorder

To assess the effects of the selective serotonin reuptake blocker fluvoxamine on noradrenergic function in patients with panic disorder, an intravenous yohimbine challenge test was administered to eight patients with panic disorder before and after 8 weeks of fluvoxamine treatment and to a parallel group of eight patients treated with placebo. Fluvoxamine treatment reduced yohimbine-induced anxiety while placebo treatment had no effect on this variable. Both fluvoxamine and placebo treatment had little effect on biochemical or physiologic responses to yohimbine.