Altered glr-1 expression is linked to EtOH cessation-mediated behavior deficits in C. elegans
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Chronic ethanol (EtOH) exposure and withdrawal are linked to worsened memory and cognitive outcomes. One target of EtOH is the glutamatergic α-amino-3-hydroxy-5methyl-4-isoxazoleproprionic acid receptor (AMPAR). Both EtOH exposure and cessation influences AMPAR expression, function, and broad glutamate signaling. Studies of EtOHrelated AMPAR regulation suggest that EtOH regulation of AMPARs drives behaviors related to dependence and memory phenotypes. However, due to the complexity of the mammalian brain, it is difficult to unravel the precise mechanism by which EtOH regulates AMPARs in mammals to modify specific memory behaviors. In C. elegans , GLR-1, an AMPAR ortholog, has tightly defined expression in relatively few neurons, has conserved regulatory mechanisms, and is linked to molecularly conserved associative behaviors including those disrupted by EtOH. Using an established paradigm that exposes worms to chronic EtOH and cessation (“withdrawal”), we examined the relationship between cessation from chronic EtOH exposure, associative memory, and GLR-1/AMPAR regulation. We found that cessation from chronic EtOH disrupts intermediate-term associative memory (ITM) in wild-type worms, phenocopying loss of GLR-1 function. Next, we found that loss of GLR-1 occludes the ITM deficit and EtOH-ceased wild-types phenocopy glr-1 loss-of-function in other glutamate-dependent behaviors. We demonstrate that cessation downregulates glr-1 , and increases CREB-mediated transcriptional activity in neurons, whereas losing CREB protects against cessationinduced glr-1 downregulation and associated behavior deficits. Overall, CREB-mediated repression of glr-1 may regulate behavior deficits in cessation.
Significance statement
Animals must navigate and remember their environments to survive. The neuronal processes underlying these behaviors can be disrupted by chronic EtOH. EtOH interacts with many processes and pathways in the complex mammalian nervous system. Here, we established a paradigm combining chronic EtOH exposure with associative memory conditioning in C. elegans to study the consequences of EtOH exposure and cessation on memory behaviors and their underlying molecular pathways. We found cessation leads to memory deficits that depend on functional excitatory transmission and master transcriptional regulator, CREB.
