Voluntary binge‐patterned alcohol drinking and sex‐specific influences on monoamine‐related neurochemical signatures in the mouse gut and brain

Abstract

Background Altered monoamine (i.e., serotonin, dopamine, and norepinephrine) activity following episodes of alcohol abuse plays key roles not only in the motivation to ingest ethanol, but also physiological dysfunction related to its misuse. Although monoamine activity is essential for physiological processes that require coordinated communication across the gut–brain axis (GBA), relatively little is known about how alcohol misuse may affect monoamine levels across the GBA. Therefore, we evaluated monoamine activity across the mouse gut and brain following episodes of binge‐patterned ethanol drinking. Methods Monoamine and select metabolite neurochemical concentrations were analyzed by ultra‐high‐performance liquid chromatography in gut and brain regions of female and male C57BL/6J mice following “Drinking in the Dark” (DID), a binge‐patterned ethanol ingestion paradigm. Results First, we found that alcohol access had an overall small effect on gut monoamine‐related neurochemical concentrations, primarily influencing dopamine activity. Second, neurochemical patterns between the small intestine and the striatum were correlated, adding to recent evidence of modulatory activity between these areas. Third, although alcohol access robustly influenced activity in brain areas in the mesolimbic dopamine system, binge exposure also influenced monoaminergic activity in the hypothalamic region. Finally, sex differences were observed in the concentrations of neurochemicals within the gut, which was particularly pronounced in the small intestine. Conclusion Together, these data provide insights into the influence of alcohol abuse and biological sex on monoamine‐related neurochemical changes across the GBA, which could have important implications for GBA function and dysfunction.

Distinct Cecal and Fecal Microbiome Responses to Stress Are Accompanied by Sex- and Diet-Dependent Changes in Behavior and Gut Serotonin

“…Cecal tissue was collected for neurochemical analysis. As previously described ( Bauer et al, 2021 ) all intestinal tissue samples were immediately acidified in 0.2N perchloric acid and stored at −80°C until Ultra High Performance Liquid Chromatography with Electrochemical Detection (UHPLC-ECD) analysis.…”

“…Tissues were thawed and then homogenized twice for 30 s at 5 m/s in a Bead Ruptor (Catalog #: 19-040E, Omni International) before centrifugation at 3,000 × g at 4 °C for 15 min. Supernatant was purified through 2–3 kDA molecular weight cut-off spin filters (Catalog #: 89132-006, VWR Life Science) after which flow-through was collected and stored at − 80 °C until analysis by UHPLC-ECD as previously described ( Bauer et al, 2021 ). The UHPLC-ECD setup included a Dionex Ultimate 3000 autosampler, a Dionex Ultimate 3000 pump, and a Dionex Ultimate 3000 RS electrochemical detector (Thermo Fisher Scientific, Sunnyvale, CA).…”

Acute Stress Exposure Alters Food-Related Brain Monoaminergic Profiles in a Rat Model of Anorexia

“…One nonstressed rat and one stressed rat were killed simultaneously by rapid decapitation without sedation or anesthetic, and brains were quickly extracted. Brain regions containing the prefrontal cortex, remaining caudal cortical area, hypothalamus, cerebellum, striatum, hippocampus, and hindbrain brainstem areas were rapidly microdissected on a glass plate placed over ice [for detailed methods, see our previous publications ( 35 , 36 )]. Microdissected brain areas were placed in preweighed cryovials containing 0.2 M perchloric acid, flash-frozen with liquid nitrogen, weighed again to obtain sample weights, and then stored at –80°C in an ultra-low freezer until ultra-HPLC (UHPLC) processing.…”

“…Microdissected brain areas were placed in preweighed cryovials containing 0.2 M perchloric acid, flash-frozen with liquid nitrogen, weighed again to obtain sample weights, and then stored at –80°C in an ultra-low freezer until ultra-HPLC (UHPLC) processing. Detailed UHPLC methodology for assessing monoamine-related neurochemicals can be found in our previous publications [see ( 35 , 36 )].…”

“…Neurochemical measurements obtained from UHPLC were corrected for by gram weight of frozen tissue for each rat (i.e., μg of neurochemical/gram of tissue). The ratio of metabolite to respective neurotransmitter concentration [i.e., 5HIAA/5HT and (HVA + DOPAC)/DA] was calculated as a measure of neurotransmitter turnover in each sample condition [see ( 35–41 )]. Moreover, imbalances between 5HT and DA activity in the brain may be of significance to AN (see Introduction).…”