Neural Perturbations Associated With Recurrent Binge Alcohol in Male and Female Rats

Abstract

Background Binge drinking, characterized by brief periods of high intoxication interspersed with periods of abstinence, appears to be particularly damaging to the brain. Binge drinking is increasing among American women, yet few preclinical studies have assessed sex differences in the neurobehavioral effects of binge alcohol. Methods Adult Long–Evans rats were administered 4 g/kg ethanol (EtOH; or an isocaloric control dose) via intragastric gavage once‐weekly. Brains were collected after 3 or 8 binge doses, and immunohistochemistry for mature neurons (NeuN), microglia (Iba1), neurogenesis (DCX), and reactive astrogliosis (vimentin) performed. Stereology was used to quantify target cell populations in the hippocampus and medial prefrontal cortex (mPFC). In a separate cohort of animals, cognition (spatial navigation and reversal learning), affect (tickling‐evoked ultrasonic vocalizations), and task‐induced c‐fos activation were assessed after 3 or 8 binge doses. Results Blood EtOH concentration did not differ significantly between females (175 ± 3.6 mg/dl) and males (180 ± 3.7 mg/dl) and did not change significantly over time, indicating that tolerance did not develop. After 3 or 8 binge doses, the number of granule neurons in the hippocampal dentate gyrus of both sexes was significantly reduced in comparison with controls, although there was no binge effect on newly generated neurons. Moreover, 8 (but not 3) binge doses significantly increased the total number of microglia and the number of partially activated microglia in the hippocampus and mPFC in both sexes. There was no detectable reactive astrogliosis (vimentin) in either region at any timepoint. There was no effect of binge alcohol on behavior outcomes in either sex, but binged rats showed increased cellular activation in the mPFC following reversal learning. Conclusions Our data indicate that recurrent binge alcohol results in similar neural damage and neuroimmune activation in alcohol‐vulnerable corticolimbic brain regions in males and females.

Changes in Affective Behavior and Oxidative Stress after Binge Alcohol in Male and Female Rats

“…There also was no effect of sex and no significant interaction ( Table 1 ). This is consistent with our prior findings that BEC does not differ by sex [ 41 ]. For plasma corticosterone, two-way ANOVA revealed a significant main effect of treatment (F(2, 50) = 3.502, p = 0.038) but not sex (F(1, 50) = 0.007, p = 0.93) and no significant interaction (F(2, 50) = 1.92, p = 0.15).…”

“…Blood alcohol levels that exceed 80 mg/dL within 2 h is considered a binge episode, though these levels could 2–3 times higher in the average American binge drinker, who consumes seven drinks per binge [ 73 ]. Here, we report equivalent BECs between male and female groups each week confirming that both groups received similar alcohol treatments regardless of weight and consistent with our prior findings showing similar BEC between the sexes [ 41 ]. Moreover, the BEC are substantial (mean 176 mg/dL) and consistent with those linked to brain damage and neurodegeneration [ 74 ].…”

“…In males, gavage increased GSH levels compared to naïve in the hippocampus and striatum. This is not likely due to stress, as gavage experience alone did not increase corticosterone, consistent with our prior evidence that gavage experience is not detectably stressful [ 41 ]. Although the control diet is isocaloric with the alcohol diet, the calories are derived from refined sugar (rather than alcohol).…”

“…The animals were separated into three groups: alcohol binge, binge control, and naïve. Within these groups, a total of 23 (11 males) rats were treated with 5 g/kg of ethanol diluted in Ensure ® -water solution (40% w / v ) once a week for 4 weeks, as we have previously shown that 3 or more weekly binge exposures is associated with significantly fewer neurons in the hippocampal dentate gyrus [ 41 ]. Eighteen binge control rats (9 males) were treated with an isocaloric Ensure ® -glucose solution, and 18 naïve rats (9 males) were handled daily and weighed once a week.…”

Astrogliosis and compensatory neurogenesis after the first ethanol binge drinking‐like exposure in the adolescent rat

“…In the CA1 area, 48 h after the two binges, there were no morphologic change in microglia and no increase in the number of CD68‐expressing cells, suggesting there was no increase in activated microglia. These results are in contradiction with a lot of literature indicating an increase in microglia activation after EtOH exposure (Alfonso‐Loeches et al, 2010; Li et al, 2019; Marshall et al, 2020; Peng & Nixon, 2021; West et al, 2021). However, EtOH exposure in these studies includes chronic or intermittent exposure over several days.…”