Astrocytic Responses to Binge Alcohol Intake in the Mouse Hindbrain

Ethanol is the most commonly used toxic chemical in human cultures. Ethanol predominantly damages the brain causing various neurological disorders. Astrocytes are important cellular targets of ethanol in the brain and are involved in alcoholic symptoms. Recent studies have revealed the diversity of astrocyte populations in the brain. However, it is unclear how the different astrocyte populations respond to an excess of ethanol. Here we examined the effect of binge ethanol levels on astrocytes in the mouse brainstem and cerebellum. Ethanol administration for four consecutive days increased the glial fibrillary acidic protein (GFAP)-immunoreactive signals in the spinal tract of the trigeminal nerve (stTN) and reticular nucleus (RN). Another astrocyte marker, aquaporin 4 (AQP4), was also increased in the stTN with a pattern similar to that of GFAP. However, in the RN, the immunoreactive signals of AQP4 were different from that of GFAP and were not changed by ethanol administration. In the cerebellum, GFAP-positive signals were found in all four astrocytic populations, and those in the Bergmann glia were selectively eliminated by ethanol administration. We next examined the effect of estradiol on the ethanol-induced changes in astrocytic immunoreactive signals. The administration of estradiol alone increased the AQP4-immunoreactivity in the stTN with a pattern similar to that of ethanol, whereas the co-administration of estradiol and ethanol suppressed the intensity of the AQP4-positive signals. Thus, binge levels of ethanol intake selectively affect astrocyte populations in the brainstem and cerebellum. Sex hormones can affect the ethanol-induced neurotoxicity via modulation of astrocyte reactivity.