Poster #263 Anatomical and Physiological Charaterization of Long Range Pathways from Hippocampus to Anterior Olfactory Nucleus |
Cosar Uzun, Meigeng Hu, Alexander Kershaw, Yaping Li, Shaolin Liu Center for Neurological Disease Research, Department of Physiology & Pharmacology, Department of Biomedical Science, University of Georgia, Athens, GA, United States |
The physiological and pathophysiological roles of the anterior olfactory nucleus (AON) have drawn increasing recognition due to its pivotal position in the olfactory system, receiving input from the olfactory bulb and sending output to several downstream structures. Additionally, AON is subject to significant top-down modulation from multiple cortical and subcortical brain regions, including the hippocapmpus (HPC). Recent studies have identified two major topographic HPC to AON pathways: intermediate HPC to the dorsal/lateral AON (iHPC-AOD/AOL) and ventral HPC to the medial AON (vHPC-AOM), both of which are crucial in encoding odor-based episodic memory. However, the physiological mechanisms driving top-down modulation of signal processing via these long-range pathways at the cellular and synaptic levels remain elusive. In this study, we addressed this question in mice by combining retrograde and anterograde tracing, whole brain clearing, optogenetics, in vivo and in vitro electrophysiology, leading to the following major findings: (1) HPC-AON projections were visualized in three dimensions within the whole-brain context; (2) spiking activities were evoked by optogenetic stimulation of HPC projections in the AON; (3) glutamate-mediated excitatory responses were observed in both pyramidal cells and interneurons upon stimulation of HPC projections. Although these results align with previous studies, our study provides the first electrophysiological evidence for the HPC-AON projections. Moving forward, further investigations will aim to characterize the pathway- and cell-type-specific synaptic transmission in the AON with the ultimate goal of advancing our mechanistic understanding of the functional significance of this particular top-down modulation. |