NMDA receptor is involved in neuroinflammation in intracerebroventricular colchicine-injected rats

Figures & data

Figure 1. Nissl granules (cresyl violet staining) of hippocampal neurons in experimental rats. (A) Nissl staining of hippocampal neurons in rats. [A1] 14-day control; [A2] 21-day control; [B1] 14-day sham-operated; [B2] 21-day sham-operated; [C1] 14-day colchicine-injected; [C2] 21-day colchicine-injected; [D1] 14-day memantine-treated ICIR; [D2] 21-day memantine-treated ICIR. Magnification = 400×, Bar = 16.18 μm. Arrows indicate Nissl granules. (B) Intensity of Nissl granules in hippocampus: *Significant decrease in ICIR rats compared to in control and sham-operated rats in 14-day (p < 0.001) and 21-day (p < 0.001) study. ^#Significant decrease in intensity in ICIR rats in 21- vs 14-day study (p < 0.001). ^$Significant increase in intensity in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study compared to in timepoint counterpart ICIR rats. ^£Significant increase in intensity in memantine-treated ICIR rats at 21- vs at 14-days (p < 0.05). Ca, 14-day control rats; Cb, 21-day control; Sa, 14-day sham-operated rats; Sb, 21-day sham-operated; ICIRa, 14-day icv colchicine-injected rats; ICIRb, 21-day icv colchicine-injected rats. Arrows indicate Nissl granules. Values shown are means ± SEM (n = 6/group).

Figure 2. Congo red staining of plaques in hippocampus of experimental rats. (A) Staining of plaques in different rats. [A1] 14-day and [A2] 21-day colchicine-injected. Memantine-treated ICIR in [B1] 14-day and [B2] 21-day study. Magnification = 400×, Bar = 16.18 μm. Arrows indicate plaques. (B) Number of plaques in hippocampus: Plaques were present in the hippocampus of ICIR rats. *Significant increase in number of plaques in ICIR rats in 21- vs 14-day study (p < 0.001). ^#Significant decrease in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs in timepoint counterpart ICIR rats. ^$Significant decrease in memantine-treated ICIR rats in 21- vs 14-day study (p < 0.05). Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 6/group).

Figure 3. Effects of memantine on TNFα levels. (A) Hippocampus. *Significant increase in TNFα in ICIR rats compared to control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant increase in ICIR rats in 21- vs 14-day study (p < 0.001). ^$Significant decrease in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs in timepoint counterpart ICIR rats. ^£Significant decrease in memantine-treated ICIR rats in 21- vs 14-day study (p < 0.05). ^€Significant decrease in memantine-treated ICIR rats in 21-day study (p < 0.001) vs in timepoint counterpart control/sham-operated rats. (B) Serum. *Significant increase in TNFα levels in ICIR rats compared to in control and sham-operated rats in 14- (p < 0.05) and 21-day (p < 0.001) study. ^#Significant decrease in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs timepoint counterpart ICIR rats. ^$Significant decrease in memantine-treated ICIR rats in 21- vs 14-day study (^ep < 0.001). ^€Significant decrease in memantine-treated ICIR rats in 14- and 21-day (p < 0.001) study vs in timepoint counter-part control/sham-operated rats. Abbreviations are as in Figure 1. Values are expressed in mean ± SEM (n = 6 in each group).

Figure 4. Effects of memantine on IL-1β levels. (A) Hippocampus. *Significant increase in IL-1β levels in ICIR rats compared to control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant increase in ICIR rats in 21- vs 14-day study (p < 0.001). ^$Significant decrease in memantine-treated ICIR rats in 14-day (p < 0.001) and 21-day (p < 0.001) studies vs in timepoint counterpart ICIR rats. ^£Significant decrease in IL-1β in memantine-treated ICIR rats in 21-day vs 14-day study (p < 0.05). (B) Serum. No significant differences in IL-1β levels were noted among the experimental groups in either study duration. Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 6/group).

Table 1. Effects of memantine on hippocampal ROS levels of experimental rats.

	ROS level in the hippocampus (% of control)			ROS level in the serum (% of control)
	14-day study			14-day study
	Control	Sham	ICIR	Control	Sham	I CIR
Without treatment	100.00	97.38	140.60	100	98.12	115.22
	±5.34	±4.67	±3.40*	±4.04	±1.58	±0.82*
Memantine treatment	88.32	87.24	130.00	100.07	98.24	99.75
	±1.33	±1.43	±7.90^$	±4.45	±1.13	±2.67^$
	21-day study			21-day study
	Control	Sham	I CIR	Control	Sham	I CIR
Without treatment	100.00	98.5	190.37	100	103.29	127.34
	±4.22	±4.84	±6.79*^,#	±4.23	±0.96	±1.28*
Memantine treatment	90.24	89.23	120.77	98.13	97.36	96.23
	±2.03	±0.91	±0.56^$	±2.60	±0.86	±1.21^$

Hippocampus: *Significant increase in ROS levels in ICIR rats compared to control and sham-operated rats in 14- (p < 0.01) and 21-day (p < 0.001) study. ^#Significantly different between ICIR rats in 21- vs 14-day study (p < 0.01). ^$Significant decrease in ROS levels in memantine-treated ICIR rats in 14- (p < 0.01) and 21-day (p < 0.01) study vs in timepoint counterpart ICIR rats.

Serum: *Significantly different in ICIR rats from control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) studies. ^$Significant decrease in ROS levels in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.01) study vs in timepoint counterpart ICIR rats. Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 6/group).

Table 2. Effects of memantine on hippocampal nitrite levels in experimental rats.

	Nitrite level in the hippocampus (% of control)			Nitrite level in the serum (% of control)
	14 day study			14 day study
	Control	Sham	I CIR	Control	Sham	I CIR
Without treatment	100.00	98.81	190.44	100.00	84.87	112.30
	± 5.06	±3.70	±3.70*	± 0.76	± 0.90	±0.31*
Memantine treatment	94.87	88.96	55.95	92.67	85.01	95.34
	±3.04	±2.78	±2.12^£	± 3.31	± 0.69	±3.07^$
	21-day study			21-day study
	Control	Sham	I CIR	Control	Sham	I CIR
Without treatment	100.00	98.75	210.92	100.00	85.50	128.10
	±4.89	±4.61	±4.07*^,#	± 0.81	±1.80	±1.07*^,#
Memantine treatment	96.21	82.33	41.07	91.33	±83.98	93.01
	±4.92	±3.06	±1.56^£	±4.57	0.25	±1.29^£

Hippocampus: *Significant increase in nitrite in ICIR rats compared to in control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) studies. ^#Significant increase in ICIR rats in 21- vs 14-day study (p < 0.001). ^$Significant decrease in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs in timepoint counterpart ICIR rats. ^£Significant decrease in memantine-treated ICIR rats in 14- and 21-day (p < 0.001) study vs in timepoint counterpart control/sham-operated rats.

Serum: *Significant increase in nitrite in ICIR rats compared to in control/sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) studies. ^#Significant increase in ICIR rats in 21-day vs 14-day study (p < 0.001). ^$Significant decrease in memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs in timepoint counterpart ICIR rats. ^£Significant decrease in memantine-treated ICIR rats in 21-day (p < 0.001) study vs in timepoint counterpart control/sham-operated rats. Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 6/group).

Figure 5. Effects of memantine on WBC phagocytic index for experimental rats. *Significant decrease in index for cells from ICIR rats compared to for cells from control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant increase for cells from memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study vs for cells from timepoint counterpart ICIR rats. ^$Significant increase for cells from memantine-treated ICIR rats of 21- vs 14-day study (p < 0.05). ^€Significant increase for WBC in memantine-treated ICIR rats in 14- and 21-day (p < 0.001) study vs for cells from timepoint counterpart control/sham-operated rats. Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 6/group).

Figure 6. Effects of memantine on splenic PMN phagocytic activity for experimental rats. *Significant increase in activity for cells from ICIR rats compared to for cells from control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant increase by cells from ICIR rats in 21- vs 14-day study (p < 0.001). ^$Significant decrease by cells from memantine-treated ICIR rats in 14- (p < 0.001) and 21-day (p < 0.001) study compared to by cells of timepoint counterpart ICIR rats. ^£Significant decrease in activity by cells from memantine-treated ICIR rats in 21- vs 14- day study (p < 0.05). Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 3/group).

Figure 7. Effects of memantine on splenic MNC cytotoxic activity. *Significant increase in activity for cells from ICIR rats compared to for cells from control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant decrease by cells from memantine-treated ICIR rats in 21-day (p < 0.001) study vs by cells of timepoint counterpart ICIR rats. ^$Significant decrease for cells from memantine-treated from ICIR rats in 21- vs 14-day study (p < 0.05). Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 3/group).

Figure 8. Effects of memantine on of splenic MNC LAI for experimental rats. *Significant decrease in LAI for cells from ICIR rats compared to by cells from control and sham-operated rats in 14- (p < 0.001) and 21-day (p < 0.001) study. ^#Significant decrease for cells from ICIR rats in 21- vs 14-day study (^c p < 0.001). ^$Significant increase for cells of memantine-treated ICIR rats in 21-day study (p < 0.001) vs for cells from time-matched ICIR rat counterparts. ^£Significant increase for cells from memantine-treated ICIR rats in 21- vs 14-day study (p < 0.05). Abbreviations are as in Figure 1. Values shown are means ± SEM (n = 3/group).

Table 3. Pearson’s correlation between inflammatory markers in the hippocampus and peripheral immune parameters in intra-cerebroventricular colchicine injected rats (ICIR) and memantine treated ICIR in the 21-day study.

	Intracerebroventricular colchicine injected rats
Hippocampal inflammatory markers	LAI of splenic MNC	PI of blood WBC	Phagocytic activity of splenic PMN cells	Cytotoxicity of splenic MNC
TNF-α	0.816 (p < 0.001)*	−0.747 (p < 0.088)	0.906 (p < 0.001)*	0.800 (p < 0.056)
IL-1β	0.945 (p < 0.212)	−0.915 (p < 0.010)^#	1.000 (p < 0.001)*	0.980 (p < 0.001)*
ROS	0.945 (p < 0.212)	−0.999 (p < 0.001)*	1.000 (p < 0.001)*	0.970 (p < 0.001)*
Nitrite	0.945 (p < 0.212)	−1.00 (p < 0.001)*	1.000 (p < 0.001)*	0.972 (p < 0.001)*
	Memantine treated intracerebroventricular colchicine injected rats
Hippocampal inflammatory markers	LAI of splenic MNC	PI ofblood WBC	Phagocytic activity of splenic PMN cells	Cytotoxicity of splenic MNC
TNF-α	0.929 (p < 0.242)	0.825 (p < 0.043)^$	0.952 (p < 0.197)	0.927 (p < 0.008)^#
IL-lβ	0.929 (p < 0.242)	0.753 (p < 0.084)	0.952 (p < 0.197)	0.965 (p < 0.002)^#
ROS	0.845 (p < 0.359)	0.728 (p < 0.101)	0.806 (p < 0.404)	0.401 (p < 0.431)
Nitrite	0.929 (p < 0.242)	0.576 (p < 0.232)	0.952 (p < 0.197)	1.000 (p < 0.001)*

Values in Pearson correlation co-efficient and the p values of significance in the parenthesis (*p < 0.001, ^#p < 0.01, ^$p < 0.05).