Fig 1.
A diagrammatic representation of the electrode implantation arrangement.
(A) The platinum-iridium cuff stimulating electrode was positioned on the left vagal nerve. (B) The recording electrode was implanted in the right hippocampal formation and the injection cannula in the right medial septum (see details in the text).
Table 1.
Experimental group and injection compounds.
Fig 2.
A schematic arrangement of protocols applied in each experimental group (I-VI).
Each 5-min pre- and post-VNS period is marked with a thin vertical line. Each 10-s VNS is marked with a thick line (see details in the text).
Fig 3.
Microphotographs (A and B) and a diagrammatic reconstruction of representative locations of the injection sites in the medial septum in three representative rat preparations of each group (18 sites, C) and representative HPC electrode tip location.
Fig 4.
The effect of MS 0.9% NaCl injection on VNS-induced HPC field potential and related power-frequency (FFT) histogram.
(A) VNS is marked with a horizontal line. The parameters of VNS are marked below this line. Arrows indicate the power-frequency histograms calculated from the analog examples of hippocampal field potentials taken pre-injection of 0.9% NaCl (control) and 15 min post-injection of 0.9% NaCl during 10 s VNS. Calibration: 1 s, 150 μV. (B) Statistical analysis (Mann-Whitney U test) of mean ± SEM power and frequency (VNS(1) vs VNS(2)).
Table 2.
Summated statistical details concerning power and frequency of VNS-induced theta rhythm after intraseptal injection of different agents (group I–group VI).
Statistical analysis: Shapiro-Wilk and Kruskal-Wallis tests.
Fig 5.
The effect of MS procaine injection on VNS-induced HPC field potential and related power-frequency (FFT) histogram.
(A) VNS is marked with a horizontal line. The parameters of VNS are marked below this line. Arrows indicate the power-frequency histograms calculated from the analog examples of hippocampal field potentials taken pre-injection of procaine (control), 15 and 60 min post-injection of procaine during 10 s VNS. Calibration: 1s, 150 μV. (B) Statistical analysis (Mann-Whitney U test) of mean ± SEM power and frequency (VNS (1) vs VNS(3)).
Fig 6.
The effect of MS atropine injection on VNS-induced HPC field potential and related power-frequency (FFT) histogram.
VNS is marked with a horizontal line. The parameters of VNS are marked below this line. Arrows indicate the power-frequency histograms calculated from the analog examples of hippocampal field potentials taken pre-injection of atropine (control), 15 and 180 min post-injection of atropine during 10 s VNS. Calibration: 1s, 150 μV.
Fig 7.
The effect of MS dicyclomine injection on VNS-induced HPC field potential and related power-frequency (FFT) histogram.
VNS is marked with a horizontal line. The parameters of VNS are marked below this line. Arrows indicate the power-frequency histograms calculated from the analog examples of hippocampal field potentials taken pre-injection of dicyclomine (control), 15 and 180 min post-injection of dicyclomine during 10 s VNS. Calibration: 1s, 150 μV.
Fig 8.
The effect of MS gallamine injection on VNS-induced HPC field potential and related power/frequency (FFT) histogram.
(A) VNS was marked with a horizontal line. Parameters of VNS were marked below this line. Arrows indicate the power-frequency histograms calculated from analog examples of hippocampal field potentials taken pre-injection of gallamine (control) and 15 min post-injection of gallamine during 10 s VNS. Calibration: 1s, 150 μV. (B) Statistical analysis (Mann-Whitney U test) of mean ± SEM power and frequency (VNS(1) vs VNS(2)).
Fig 9.
The effect of MS McN-A343 injection on VNS-induced HPC field potential and related power-frequency (FFT) histogram.
(A) VNS is marked with a horizontal line. The parameters of VNS are marked below this line. Arrows indicate the power-frequency histograms calculated from analog examples of hippocampal field potentials taken pre-injection of McN-A343 (control), 15 and 60 min post-injection of McN-A343 during 10 s VNS. Calibration: 1 s, 150 μV. (B) Statistical analysis (Mann-Whitney U test) of mean ± SEM power and frequency (VNS(1) vs VNS(2), and VNS(1) vs VNS(3)).