Glutamatergic and GABAergic puncta and their ratio in the hippocampal CA1 region. (a) Representative confocal images of VGLUT1 immunostaining in the stratum oriens (SO) of wild type (WT) and TgCHRNA5/A3/B4 (Tg) mice that received either saline (Sal) or nicotine (Nic, 3.25 mg/Kg/d) for 7 d, Scale bar 5 μm. (b) Quantification of VGLUT1 puncta showing that Tg mice presented reduced glutamatergic puncta in SO and stratum radiatum (SR), as compared to their WT littermates. Chronic infusion of nicotine rescued the reduced density of VGLUT1 puncta in the CA1 SO of Tg mice, but caused opposite effects in WT, leading to a significant decrease both in SO and SR. (c) Representative confocal images of VGAT immunostaining in the SO of mice with the conditions indicated, Scale bar 5 μm. (d) Quantification of VGAT puncta showing reduced GABAergic input in SO and SR of Tg mice, compared to WT. Chronic nicotine increased VGAT puncta in SO in Tg. In contrast, the same treatment reduced VGAT puncta in SO and SR in WT mice. (e) The glutamatergic (Glu)/GABAergic ratio in CA1 SO and SR regions was increased in Tg mice, as compared to WT. Chronic nicotine treatment rescued the increased Glut/GABA ratio in Tg, with no effect in WT (n = ≥100 images animal; 4-5 animals/group from ≥ 3 experiments). *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001.