Noise Exposure Alters Glutamatergic and GABAergic Synaptic Connectivity in the Hippocampus and Its Relevance to Tinnitus

Figure 8

Tinnitus animals exhibit diminished recovery of VGAT labeling relative to no-tinnitus animals in the dentate gyrus (DG) and areas CA3 and CA1. (a) Representative images of VGAT labeling from distal molecular layer of the DG (DG-ml_d), stratum oriens of CA3 (CA3-s.o), and stratum oriens of CA1 (CA1-s.o) at 400x magnification; . (b–d) Mean (±SEM) change of VGAT density (normalized to respective control) in the DG (b), CA3 (c), and CA1 (d) in two-week and 12-week postnoise-exposure animals. Compared to 2-week postexposure animals (2w), 12-week postexposure animals (ENT and ET) largely recovered to or near to baseline levels. Tinnitus animals (ET) exhibit better recovery of VGAT labeling relative to no-tinnitus animals (ENT) in the dentate gyrus(DG) and areas CA3 and CA1. ^#For comparison to the paired controls (dashed line), . For comparison between 2w, ENT, and ET groups, . ml_d: distal region of molecular layer; ml_m: middle region of molecular layer; ml_p: proximal region of molecular layer; g: granule cell layer; h: hilus; s.o: stratum oriens; s.p: stratum pyramidale; s.l: stratum lucidum; s.r: stratum radiatum; s.r_p: proximal region of stratum radiatum; s.r_d: distal region of stratum radiatum; s.lm: stratum lacunosum-moleculare.

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