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Diazepam-induced adaptive plasticity revealed by alpha1 GABAA receptor-specific expression profiling
Laura Huopaniemi1, Ruth Keist, Ann Randolph
1Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland.
Journal of Neurochemistry
|March 11, 2004
Summary
Diazepam, a benzodiazepine, reduces specific gene expression related to neuronal plasticity and neurotrophic responses. This effect, mediated by alpha1 GABAA receptors, may explain long-term changes in brain function.
Area of Science:
- Neuroscience
- Pharmacology
- Molecular Biology
Background:
- Benzodiazepines are widely used for sedation and tranquilization, primarily acting through alpha1-containing GABAA receptors.
- The precise signal transduction pathways activated by benzodiazepines beyond the receptor remain incompletely understood.
Purpose of the Study:
- To investigate the downstream molecular effects of diazepam on gene expression in the brain.
- To elucidate the role of the alpha1 GABAA receptor subunit in mediating diazepam's effects on transcript levels.
Main Methods:
- Microarray analysis was employed to compare transcript level changes in the cerebral cortex of wild-type and alpha1(H101R) mutant mice following acute diazepam administration.
- The alpha1(H101R) mouse model possesses a point mutation rendering the alpha1 GABAA receptor subunit insensitive to diazepam.
Main Results:
- In wild-type mice, diazepam significantly down-regulated transcripts including CaMKIIalpha, BDNF, MKP, GIF, c-fos, and NGI-A.
- These transcript changes were absent in alpha1(H101R) mice, indicating mediation via the alpha1 GABAA receptor subunit.
- The down-regulation of CaMKIIalpha transcript persisted for at least 40 hours post-treatment, suggesting long-term effects.
Conclusions:
- Diazepam's sedative effects are associated with the down-regulation of genes critical for neuronal plasticity and neurotrophic signaling.
- The alpha1 GABAA receptor is essential for mediating these transcriptomic changes.
- Persistent alterations in gene expression, particularly CaMKIIalpha, may contribute to rebound phenomena, tolerance, and dependence observed with chronic benzodiazepine use.