Effect of ivabradine on cognitive functions of rats with scopolamine-induced dementia

Figures

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  Figure 1. Analysis of behavioral tests: (A) Effect of ivabradine on time taken to enter the dark compartment in passive avoidance test in the first day which presented as IL in scopolamine induced dementia (in seconds). (B) Effect of ivabradine on time taken to enter the dark compartment in passive avoidance test which presented as STL in scopolamine induced dementia (in seconds). PA passive avoidance, IL initial latency, STL step-through latency. (C) Effect of ivabradine on time spent on the target quadrant where the platform was located during the probe trial in seconds in scopolamine induced dementia. (D) Effect of ivabradine on time taken to locate the position of the platform is presented as escape latency during the probe trial in seconds in scopolamine induced dementia (in seconds). (A–C) Data have been analyzed by using one way ANOVA p < 0.01. (E) The effect of ivabradine on the time spent exploring objects in the sample phase in scopolamine induced dementia in seconds. Values are analyzed using by two way ANOVA P = 0.8532 and expressed as mean ± SEM. of (8–10) rats. (F) The effect of ivabradine on the time spent exploring objects during novel object recognition test in scopolamine…

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  Figure 2. Analysis of inflammatory cytokines and oxidative stress: (A) Effect of ivabradine on hippocampal TNF-α level of scopolamine treated rats. (B) Effect of ivabradine on hippocampal inflammatory cytokines (IL-2) level of scopolamine treated rats. (C) Effect of ivabradine on hippocampal inflammatory cytokines (IL-6) level of scopolamine treated rats. (D) Effect of ivabradine on hippocampal lipid peroxidase (MDA) level of scopolamine treated rats. (E) Effect of ivabradine on hippocampal superoxide dismutase (SOD) level of scopolamine treated rats. (F) Effect of ivabradine on hippocampal total antioxidant capacity (TAC) level of scopolamine treated rats. *Significant (P > 0.05) difference from control group and #Significant (P > 0.05) difference from dementia control group.

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  Figure 3. showing the microscopic features of scopolamine administrated groups: (A–C) the pyramidal layers of the control group I. (D–F) In group II there were signs of mild neurodegeneration, such as, Balloon cells (BC) with a remnant of the cytoplasm encircling the balloon. (G–I) In group III, there were more signs of neurotoxicity after the ES, for example complete ballooning of the entire cells (balloon achromatic cells) in all hippocampal subfields. (J–L) One rat of the ES group (III) showed a highly deformed hippocampus. CA1-CA2 pyramidal cells had been deformed with dysmorphic shapes and CA3 disappeared and few vacuoles were seen instead.

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  Figure 4. Showing the microscopic features of scopolamine administrated groups: (A,B) the granular layer and cells in the hilum of the control. (C,D) In group II, most of the granular layers and hilum cells became BC cells. (E,F) In group III, both densely stained elongated cells and a lot of BC were shown in the granular layer and the cells of the hilum. (G) A rat of the ES group showed a severely deformed hippocampus, where the DG had no hilum and the granular cells were severely reduced, with only a few remaining condensed, and dysmorphic cells and separated by large spaces.

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  Figure 5. Showing pyramidal layers of the low and high dose ivabradine and donepezil treated groups. More normal healthy cells and less deformed cells were seen in the pyramidal layer of the three groups. (A–C) The pyramidal layer of ES group III. (D–F) In group IV, low ivabradine dose, the thickness and the number of the pyramidal layers in CA1, CA2 and CA3 were increased. (G–I) In group V, high ivabradine dose, the thickness of the pyramidal layer increase in CA1, CA3 and CA3 and there were significant distances between cells. (J–L) In group VI, donepezil, the shape was comparable to that of the high ivabradine dose. Additionally, the pyramidal layer of CA2 and CA3 showed few densely stained cells. (M–O) Quantification of the thickness of pyramidal layers in all groups of the experiment including the control (I), the scopolamine (II), the ES (III), the low ivabradine (IV) and high dose (V)of ivabradine and donepezil (VI) on of ES administrative group.

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  Figure 6. Showing the dentate gyrus of low and high dose ivabradine and donepezil treated groups. (A,B) The cells degenerated in the granular layer and in the hilum of the ES group III. (C,D) Group IV, low ivabradine dose. (E,F) Group V, high ivabradine dose, (G,H) group VI, donepezil. In the later three groups, the mean number of the cells per section in the hilum increased. The inner layers of the granular layer were dense and small. (M–O) Quantification of the thickness of granular layer of the dentate gyrus in all groups of the experiment including the control (I), the scopolamine (II), the ES (III), the low ivabradine (IV) and high dose (V) of ivabradine and donepezil (VI) on of ES administrative group.

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  Figure 7. Showing the amyloid plaques stained with congo red. On the left panel, there are many plaques of both large and small sizes in the extended scopolamine group. In the middle, after low ivabradine the plaques become less frequent and of small sizes only. The plaques disappear from the cortex and hippocampus in case of ES group.

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  Figure 8. Expression of HCN in scopolamine administrated groups in CA: (A–C) The HCN1 immunoreactivity in the pyramidal layer of CA of the control group. (D–F) The HCN1 immunoreactivity in group II was comparable to that of the control group in CA. (G–I) The HCN1 immunoreactivity decreased significantly in ES group III in CA.

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  Figure 9. The expression of HCN1 in scopolamine administrated groups expression in DG and hilum: (A,B) The HCN1 immunoreactivity of the control. (C,D) The HCN1 immunoreactivity in group II was comparable to that of the control group in DG and hilum. (E) The HCN1 expression decreased significantly after ES in group III in DG and hilum.

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  Figure 10. The expression of HCN in low and high doses of ivabradine and donepezil groups in CA: (A–C) The HCN1 immunoreactivity of the ES group III in CA. The HCN1 expression in CA increased in group IV, low ivabradine dose (D–F), increased dramatically in group V, high ivabradine dose (G–I). In group VI, donepezil (J–L), was comparable to that of the high ivabradine treated group. (M–O) Quantification of the optical density of HCN1 immunoreactivity in CA1 (M), in CA2 (N) and in CA3 (O) in different groups.

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  Figure 11. The expression of HCN in low and high doses of ivabradine and donepezil groups in DG and hilum: the high ivabradine dose and donepezil-treated rats showed a comparable increase in HCN1 immunoreactivity, which was much higher than the control group. Note that the hilum disappeared in the same group. (H,I) Quantification of the optical density of HCN1 immunoreactivity in DG (H) and in the cells of the hilum (I) in different groups.

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  Figure 12. The timeline graphical representation. Sco scopolamine, IVA ivabradine, PAT passive avoidance test, MWM Morris water maze, NOR novel object recognition.