Altered synaptic plasticity of the longitudinal dentate gyrus network in noise-induced anxiety

Hippocampal interlamellar cell–cell connectome that counts

“…Moreover, interlamellar axons easily escape detection, mainly because they are too thin to be visualized and are weakly identified via classical staining and electrophysiological methods (Choi et al, 2021 ; Yang et al, 2014 ). Along with previous studies that have observed the presence of interlamellar axons (Amaral & Witter, 1989 ; Claiborne et al, 1986 ; Henze et al, 2000 ), there are several lines of anatomical and electrophysiological evidence showing connections between hippocampal regions, such as CA1‐CA1, CA3‐CA3, and DG‐DG connections (Choi et al, 2021 ; Pak et al, 2022 ; Strange et al, 2014 ; Sun et al, 2018 ; Yang et al, 2014 ). In this review, we describe the anatomical and physiological aspects of interlamellar networks along the longitudinal axis, which corresponds to the septotemporal (or dorsoventral) axis in rodents and the anterior–posterior axis in primates (Table 1 ).…”

“…These data suggest the presence of a DGGC‐DGGC connection along the longitudinal axis (Figure 2 ). A more recent study using two‐photon axon imaging confirms the presence of direct and bidirectional longitudinal axons between granule cells in the DG (Choi et al, 2021 ; Pak et al, 2022 ). The primary axon of a DG granule cell heading to the CA3 region bifurcates to the longitudinal direction.…”

“…Longitudinal axons have denser varicosities and are thinner than the primary axons that head toward the CA3 area, suggesting heavy synaptic weight and rapid signal transfer along the longitudinal axis (Table 2 ). At the circuit level, enhanced synaptic excitability and plasticity are observed in the DG‐DG network (Table 3 ) (Pak et al, 2022 ). In local field recordings with longitudinal hippocampal slices, the longitudinal DG‐DG connection shows more robust synaptic efficacy and long‐term potentiation (LTP) than the transverse network, implicating a pivotal role of longitudinal axons in the regulation of cognition and behavior (Pak et al, 2022 ).…”

“…At the circuit level, enhanced synaptic excitability and plasticity are observed in the DG‐DG network (Table 3 ) (Pak et al, 2022 ). In local field recordings with longitudinal hippocampal slices, the longitudinal DG‐DG connection shows more robust synaptic efficacy and long‐term potentiation (LTP) than the transverse network, implicating a pivotal role of longitudinal axons in the regulation of cognition and behavior (Pak et al, 2022 ).…”

“…The colors indicate representative neurons and their projections: red, DG; blue, CA3; black, CA2; green, CA1; orange, EC. Adapted from previous studies (Andersen et al, 1969 , 1971 ; Bliss & Lomo, 1973 ; Choi et al, 2021 ; Pak et al, 2022 ; Sloviter & Lomo, 2012 ; Steffenach et al, 2002 ; Strange et al, 2014 ; Sun et al, 2018 ; Witter et al, 1989 ; Yang et al, 2014 ). CA3, cornu ammonis 3; DG, dentate gyrus; EC, entorhinal cortex layer.…”