Damage incurred by traumatic brain injury is believed to be caused in part by mass depolarization leading to excitotoxicity . One way in which progesterone helps to alleviate some of this excitotoxicity is by blocking the voltage-dependent calcium channels that trigger neurotransmitter release.  It does so by manipulating the signaling pathways of transcription factors involved in this release. Another method for reducing the excitotoxicity is by up-regulating the GABA A , a widespread inhibitory neurotransmitter receptor. 
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