An NMDA-R mediated short-term memory resistant to anesthesia in adult Danio rerio

Memory in animals is labile in the early phase post-training. Memory in the early phase has been shown to be disrupted by treatments such as electroconvulsive shock or cold-shock (Quinn and Dudai, 1976). Using hypothermic shock and other pharmacological interventions, the various underlying memory pathways in Drosophila can be identified as an immediate short-lasting anesthesia sensitive memory and a delayed anesthesia resistant memory which is followed by a more stable protein synthesis dependent long-term memory (Margulies et al., 2005). In another ectothermic animal, Danio rerio, a popular vertebrate model, we ask if such a memory component exists which is sensitive to hypothermic disruption. To test this, we developed a fear conditioning assay with a green light at the bottom of the tank as the conditioned stimulus (CS) and electric shock as the unconditioned stimulus (US). We also standardized a cold anesthesia protocol in adult zebrafish to induce stage V anesthesia. The learning/memory was found to be NMDA-R mediated. Cold anesthesia as well as tricaine mediated anesthesia did not significantly affect the early-acting memory trace induced by a fear-conditioning protocol in adult zebrafish. We suggest future directions to tease out the underlying memory components in the early phase of memory in zebrafish.