Cognitive effects of electro-acupuncture and pregabalin in a trigeminal neuralgia rat model induced by cobra venom

Figures & data

Figure 1 Pictures showing the EA points (1–42) and EA procedure.

Note: The rat showed no signs of distress during EA.
Abbreviation: EA, electro-acupuncture.

Figure 2 Frequency and length of face grooming and exploratory behavior were observed before the operation and at eight postoperative time points.

Notes: (A–D) No significant differences among groups were found before and 3 days after the operation (P>0.05). At postoperative day 6, the frequency and length of exploratory behavior of rats after cobra venom injection showed remarkable decrease in comparison to the rats in sham-operated group (*: compared between cobra venom and sham-operated groups, frequency: *P=0.011, length: *P=0.041; ^&: compared between EA and sham-operated groups, frequency: ^&P=0.007, length: ^&P=0.024; ^#: compared between pregabalin and sham-operated groups, frequency: ^#P=0.002, length: ^#P=0.019), while the frequency and length of grooming behavior showed increase in comparison to the rats in sham-operated group (*: compared between cobra venom and sham-operated groups, frequency: *P=0.003, length: *P=0.028; ^&: compared between EA and sham-operated groups, frequency: ^&P=0.005, length: ^&P=0.002; ^#: compared between pregabalin and sham-operated groups, frequency: ^#P=0.011, length: ^#P=0.040). Significant differences were observed at postoperative day 20 after EA and pregabalin treatment, respectively, compared to cobra venom group (*: compared between cobra venom and sham-operated groups, frequency of exploratory behavior: *P=0.003, length of exploratory behavior: *P=0.012, frequency of grooming behavior: *P=0.031, length of grooming behavior: *P=0.003; ⁺: compared between EA and cobra venom groups, frequency of exploratory behavior: ⁺P=0.040, length of exploratory behavior: ⁺P=0.040, frequency of grooming behavior: ⁺P=0.011, length of grooming behavior: ⁺P=0.002; ⁻: compared between pregabalin and cobra venom groups, frequency of exploratory behavior: ⁻P=0.038, length of exploratory behavior: ⁻P=0.037, frequency of grooming behavior: ⁻P=0.001, length of grooming behavior: ⁻P=0.001).
Abbreviation: EA, electro-acupuncture.

Figure 3 (A–D) Morris water maze training. (E, F) Morris water maze probe trial.

Notes: (A, B) No differences were found in the latency curve among all groups before the model was established and at 1 week after the operation. (C, D) At 3 and 5 weeks after the operation, the latency curve in the cobra venom and pregabalin groups showed a slower learning rate, compared to the sham-operated group (*: compared between cobra venom and sham-operated groups, *P<0.05; ^#: compared between pregabalin and sham-operated groups, ^#P<0.05). However, the EA group showed a faster learning rate compared with cobra venom group (^&: compared between EA and cobra venom groups, ^&P<0.05). Data represent mean±SD (repeated measures one-way ANOVA followed by LSD t-test). (E) No differences were found in the number of platform crossings among all groups 7 days before and after the operation. At postoperative days 21 and 35, the number of platform site crossings showed a decrease in cobra venom group compared with that in the sham-operated group (*: compared between cobra venom and sham-operated groups, *P<0.05). However, the number of platform site crossings showed an increase in EA group compared with the cobra venom group (^&: compared between EA and cobra venom groups, ^&P<0.05). Meanwhile, the number of platform site crossings showed a decrease in pregabalin group compared with the sham-operated group (^#: compared between pregabalin and sham-operated groups, ^#P<0.05), while there was no difference between EA and sham-operated groups or between cobra venom and pregabalin groups. (F) The average percentages of the total probe trial time in the target quadrant (without the platform). No differences were found in the average percentages of the total probe trial time in the target quadrant among all groups 7 days before and after the operation. At postoperative days 21 and 35, the average percentages of the total probe trial time in the target quadrant showed a decrease in cobra venom group compared with that in sham-operated group (*: compared between cobra venom and sham-operated groups, *P<0.05). However, the average percentages of the total probe trial time in the target quadrant showed an increase in EA group compared with cobra venom group (^&: compared between EA and cobra venom groups, ^&P<0.05). Meanwhile, the average percentages of the total probe trial time in the target quadrant showed a decrease in pregabalin group compared with sham-operated group (^#: compared between pregabalin and sham-operated groups, ^#P<0.05), while there was no difference between EA group and sham-operated group or between cobra venom group and pregabalin group.
Abbreviations: ANOVA, analysis of variance; EA, electro-acupuncture.

Figure 4 (A) The normal Gasserian ganglion, (B) medulla oblongata and (C) hippocampus. Electron microscopy showed that the structure of myelin sheaths and axon was entire (marked by arrows). (D) Gasserian ganglion, (E) medulla oblongata and (F) hippocampus with cobra venom injection. Electron microscopy showed severe demyelination and loss of axons (marked by arrows). The structure of myelin was disturbed and the layers were altered. The ultrastructure of neurons in hippocampus was altered obviously. Swelling of mitochondria and severe vacuolar degeneration in cells were observed. (G) Gasserian ganglion, (H) medulla oblongata and (I) hippocampus after EA treatment. Electron microscopy showed mild demyelination and loss of axons (marked by arrows). Microscopic examination of hippocampus neurons showed mild vacuolar degeneration and swelling of mitochondria in cells. (J) Gasserian ganglion, (K) medulla oblongata and (L) hippocampus after pregabalin treatment. Electron microscopy showed mild demyelination and loss of axons in part (marked by arrows). Microscopic examination of hippocampus neuron showed moderately severe vacuolar degeneration and swelling of mitochondria in cells.

Abbreviation: EA, electro-acupuncture.

Figure 5 The fEPSP slope reveals differential time-dependent alternations in hippocampus CA1 in different groups.

Notes: Vertical axis indicates the maximal fEPSP slope. Lateral axis indicates the time course of changes. Baseline is set at 100%. Black curve, sham-operated slices (n=10); red curve, cobra venom slices (n=10); blue curve, EA-treated slices (n=10) and green curve, slices treated by pregabalin (n=10). Data shown are mean±SD. P<0.05, significantly different as indicated. The four groups presented significant differences (ANOVA, two-tailed) in fEPSP slope at postoperative day 50, when compared with the baseline records. The fEPSP slope collected from the sham-operated group showed a significant increase compared to those collected from rats in the cobra venom group at the indicated times (*P=0.029). Nevertheless, the fEPSP slope showing responses in rats in the EA group showed an increase compared to the cobra venom group (^&P=0.001), but showed no difference with the sham-operated group. Meanwhile, the fEPSP slope showing responses in rats in the pregabalin group showed a significant decrease compared to the sham-operated group (^#P=0.046), while it showed no difference with the cobra venom group.
Abbreviations: ANOVA, analysis of variance; EA, electro-acupuncture; fEPSP, field excitatory postsynaptic potential; TBS, Theta-burst stimulation.