Monday, February 3, 2025 11:05am to 12pm
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1905 Colorado Avenue, Boulder, CO 80309
The Department of Psychology and Neuroscience proudly presents Dr. Giacomo Maddaloni, postdoctoral fellow in the Department of Genetics at Harvard Medical School.
Title: Adaptation to seasonal changes in daylength via dynamic serotonin-glutamate neurotransmitter segregation
Abstract: The neural capacity to decode seasonal changes in daylength (photoperiod) and accordingly adjust physiology and behavior is vital to survival and well-being, yet underlying brain mechanisms remain elusive. I will present a previously unknown neural circuit and system of axon branch-specific and reversible neurotransmitters deployment that prove critical for behavioral and sleep adaptation to photoperiods. We found that the dual serotonin-glutamate neuron type called En1-Pet1 located in the mouse Median Raphe segregates serotonin versus VGLUT3 (proxy for glutamate) to different axonal branches innervating specific brain regions involved in circadian rhythm and sleep/wake. Such configuration was stable across the sleep/wake cycle; however, it reorganized on photoperiod change. Axonal boutons but not cell soma changed neurochemical phenotype upon shift away from equinox light/dark conditions that reversed upon equinox return. When this remodeling was genetically disabled, sleep/wake periods, activity, and clock gene expression failed to synchronize to the new photoperiod. Combining intersectional rabies virus tracing and projection-specific neuronal silencing, we delineated a Preoptic Area-to-En1Pet1 connection responsible for decoding the photoperiodic inputs, driving the neurotransmitter reorganization and promoting synchronization. Our results reveal a previously unrecognized brain circuit and periodic, branch-specific neurotransmitter deployment that regulates organismal adaptation to photoperiod change.
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