Effects of alcohol exposure on the glutamatergic system: a combined longitudinal 18F‐FPEB and 1H‐MRS study in rats. (23rd May 2018)

• Record Type: Journal Article
• Authors: de Laat, Bart; Weerasekera, Akila; Leurquin‐Sterk, Gil; Gsell, Willy; Bormans, Guy; Himmelreich, Uwe; Casteels, Cindy; Van Laere, Koen
• Is Part Of: Addiction biology. Volume 24:Number 4(2019)
• Page Start: 696
• Page End: 706
• Publication Date: 2018-05-23
• Subjects: alcohol -- magnetic resonance spectroscopy -- metabotropic glutamate receptor 5 -- open field test -- positron emission tomography -- preclinical; Substance abuse -- Periodicals; Substance abuse -- Physiological aspects -- Periodicals; Substance-Related Disorders -- periodicals; 616.86
• DOI: 10.1111/adb.12635
• Languages: English
• ISSNs: 1355-6215

Abstract

Abstract : In a longitudinal rat model of alcohol consumption, we showed that exposure to alcohol decreased the concentration of glutamate in the prefrontal cortex, whereas a normalization occurred during abstinence. 18F‐FPEB PET scans revealed that pre‐exposure mGluR5 availability in the nucleus accumbens was associated with future alcohol preference. Finally, alcohol exposure induced a decrease in mGluR5 availability in the bilateral hippocampus and amygdala compared with baseline, and in the hippocampus and striatum compared with saccharin (Figure). Abstract: To study the role of the glutamatergic system in alcohol abuse disorders, we conducted a longitudinal study of alcohol exposure in rats. Rats were followed with 1 H‐magnetic resonance spectroscopy during a baseline, exposure and abstinence phase to measure prefrontal glutamate and glycine concentrations. Additionally, 18 F‐FPEB PET was used to assess metabotropic glutamate receptor 5 (mGluR5) availability before and after exposure to alcohol or saccharin. Finally, individual anxiety levels were assessed with an open field test at baseline. We found that the total distance traveled in the open field test and mGluR5 availability in the nucleus accumbens were associated with future alcohol preference ( P = 0.02). Furthermore, prefrontal glutamate concentration decreased significantly during alcohol exposure (> −1.25 ± 0.55 mmol/L, P = 0.038), but normalized during abstinence. Finally, 18 F‐FPEB PET showed that self‐administration of alcohol resulted in decreased mGluR5 availability in the hippocampus (>14 ± 3 percent, pCluster = 0.047) and amygdala (>16 ± 2 percent, pCluster = 0.004), whereas saccharin induced decreases in the prefrontal cortex (>11 ± 1 percent, pCluster = 0.035) and hippocampus (>15 ± 2 percent, pCluster = 0.003). A direct comparison of both groups showed differences in mGluR5 availability in the bilateral striatum (−2 ± 4 percent versus +2 ± 2 percent, pCluster = <0.0001) and hippocampus (−16 ± 4 percent versus −5 ± 4 percent, pCluster = <0.0001). In conclusion, this study corroborates the anxiolytic effect of alcohol and provides evidence for mGluR5 downregulation in the amygdala as potential underlying mechanism. Saccharin and alcohol differentially affect prefrontal glutamate concentrations, but both induce an mGluR5 decrease, potentially to modulate the dopamine release elicited by these drugs.