Shiromani, P. J. | bioRxiv Science

bioRxiv2021

Divergent sex differences in functional brain connectivity networks in excessively drinking C57BL/6J mice

Individuals with alcohol use disorder continue to drink in excess despite the health and societal consequences, and the rate of problematic drinking and alcohol-related harms is increased in women. Clinical imaging studies report widespread adaptations in brain structure after chronic, heavy drinking, and alcohol-related cues enhance brain reactivity in reward-related regions. In rodents, alcohol drinking induces expression of the immediate early gene c-Fos, which can be a marker of cellular activity, across multiple brain regions. Recent evidence also suggests that abstinence from chronic intermittent alcohol exposure can produce mesoscale changes in c-Fos expression. However, there is a substantial gap in our understanding of how excessive drinking affects functional connectivity networks to influence alcohol-seeking behaviors. For this study, male and female C57BL/6J mice were given access to either water or a choice between water and ethanol in the intermittent access drinking model for 4 weeks. After a short-access drinking session, whole brains from high alcohol drinking male and female mice and water drinking controls were then subjected to c-Fos immunolabeling, iDISCO+ clearing, light sheet imaging, and whole-brain c-Fos mapping. Correlation matrices were then generated and graph theoretical statistical approaches were used to determine changes in functional connectivity across sex and drinking condition. We observed robust sex differences in the network of c-Fos+ cells in water drinking mice, and excessive alcohol drinking produce divergent and robust changes in functional network connectivity in male and female mice. In addition, these analyses identified novel hub regions in excessively drinking mice that were unique for each sex. In conclusion, the whole-brain c-Fos mapping analysis identified sex difference in functional network connectivity and unique and understudied regions that may play a critical role in controlling excessive ethanol drinking in male and female mice.

neuroscience↗

bioRxiv2020

Vesicular GABA-transporter neurons in the zona incerta are maximally active during non rapid-eye movement (NREM) and rapid-eye movement (REM) sleep

Sleep and wake are opposing behavioral states controlled by the activity of specific neurons. The neurons responsible for sleep/wake control have not been fully identifed due to the lack of in-vivo high throughput technology. We use the deep-brain calcium (Ca2+) imaging method to identify activity of hypothalamic neurons expressing the vesicular GABA transporter (vGAT), a marker of GABAergic neurons. vGAT-cre mice (n=5) were microinjected with rAAV-FLEX-GCaMP6M into the lateral hypothalamus and 21d later the Ca2+ influx in vGAT neurons (n=372) was recorded in freely-behaving mice during waking (W), NREM and REM sleep. Post-mortem analysis revealed the lens tip located in the zona incerta/lateral hypothalamus (ZI-LH) and the change in fluorescence of neurons in the field of view was as follows: 54.9% of the vGAT neurons had peak fluorescence during REM sleep (REM-max), 17.2% were NREM-max, 22.8% were wake-max while 5.1% were both wake+REM max. Thus, three quarters of the recorded vGAT neurons in the ZI-LH were most active during sleep. In the NREM-max group Ca2+ fluorescence anticipated the initiation of NREM sleep onset and remained high throughout sleep (NREM and REM sleep). In the REM-max neurons Ca2+fluorescence increased before the onset of REM sleep and stayed elevated during the episode. Activation of the vGAT NREM-max neurons in the zona incerta and dorsal lateral hypothalamus would inhibit the arousal neurons to initiate and maintain sleep.

neuroscience↗