Gene expression profile of neurodegeneration induced by α _1B-adrenergic receptor overactivity: NMDA/GABA_A dysregulation and apoptosis

The α₁-adrenergic receptors (α₁ARs) play an important role in mediating sympathetic neurotransmission in peripheral organ systems; however, central α₁ARs are not well characterized. Additionally, due to the lack of sufficiently subtype-selective drugs or high avidity antibodies, the contribution of each α ₁AR subtype to various central functions is currently unclear. Transcription regulation through α₁AR subtypes in the CNS is also unknown. Of interest, transgenic mice that systemically overexpress the α_1BAR show central symptoms that include age-progressive impaired mobility, neurodegeneration and susceptibility to epileptic seizure. To investigate the molecular basis of this phenotype, oligonucleotide microarray studies of whole brains of various ages were carried out to compare gene expression profiles between transgenic and normal brains. The results indicated changes in expression of apoptotic, calcium regulatory, neurodegenerative and genes involved in neurotransmission. Defects in regulation of intracellular calcium are known to play a role in cell death; thus, these genes may provide clues as to the molecular basis of α _1BAR-induced neurodegeneration. Epilepsy is a disorder that can be caused by an imbalance between excitatory (e.g. glutamate) and inhibitory (e.g. GABA) signals. Microarray analysis of transgenic brains showed increased N-methyl-D-aspartate (NMDA) receptors and decreased GABA_A, which were confirmed with immunohistochemistry, western blot and radioligand binding studies. The α_1BAR also co-localized with the glutamatergic distribution, suggesting a glutamate imbalance as a molecular rationale for the epileptic seizures.