Gap Junctions Underlying Labile Memory

Neuroscientists are eager to decipher the mechanisms underlying learning and memory in the brain. Whether gap junction plays a role remains uncertain. The olfactory associative memory in genetically tractable fruit fly, Drosophila melanogaster, provides great opportunity to address this question because simple circuits and few genes underlie the well-characterized memory. Mushroom body (MB), the learning and memory center, is composed of 2000 intrinsic Kenyon cells (KCs) that represent the odor information. As a result of learning, the neuroplasticity of a sparse population of KCs representing the conditioned odor changes and eventually leads to conditioned behavioral outcome. Anterior paired lateral (APL) and dorsal paired medial (DPM) neurons are two modulatory neurons broadly innervating the whole MB and both involved in memory consolidation. Here, we showed by dye coupling that the APL and DPM neurons form a gap-junctional communication. Knockdown of inx7 and inx6 in the APL and DPM neurons, respectively, abolished the labile memory component while leaving the other consolidated memory component and learning ability unaffected, indicating a specific role of the heterotypic gap-junctional communication between APL and DPM neurons. Labile memory is a memory component that would be totally erased by anesthetization-induced retrograde amnesia. We proposed that the gap junctions between APL and DPM neurons sustain labile memory throughout the intermediate time course.