Molecular and Neural Circuit Mechanisms Underlying Sexual Experience-dependent Long-Term Memory in Drosophila.

The neural and molecular underpinnings of sexual experience-dependent long-term memory (SELTM) in male Drosophila melanogaster remain poorly understood, despite its significance for reproductive success. Here, we dissect the role of a specific class of neurons, termed 'Yuelao' (YL) neurons, in the formation of SELTM and the associated molecular pathways. We employed a combination of genetic manipulations, immunohistochemistry, and behavioral assays in Drosophila to investigate the function of YL neurons and their molecular interactors in SELTM. Utilizing the RNA sequencing data and transgenic tools, we delineated the neural circuits involved in taste and pheromone processing relevant to SELTM. Our findings reveal that the YL neurons, expressing the Orb2 scaffolding protein, are indispensable for the formation of SELTM following sexual experience. These neurons are regulated by the neuromodulator short neuropeptide F (sNPF) and its receptor (sNPF-R), which modulate glutamate release via NMDAR2. We demonstrate that sexual experience triggers synaptic plasticity in YL neurons, characterized by an increase in dendritic and presynaptic terminal areas, and a decrease in intracellular calcium levels. Furthermore, we show that YL neurons are specialized for the generation of appetitive sexual experience-dependent memory and project to brain regions implicated in memory formation. Our study uncovers the YL neurons as a key neural substrate for SELTM in Drosophila, shedding light on the molecular and circuit mechanisms that mediate the formation of long-term memories following sexual experience. These findings provide novel insights into the neural basis of taste-related memory and have broader implications for understanding the interplay between experience, memory formation, and behavior.