Colitis can reduce the cingulate cortex neuronal density in rats.

Background and aim: Hyperalgesia and hypersensitivity in patients with Inflammatory Bowel Disease (IBD) can be related to central nervous system (CNS) changes, particularly in the pain pathways. The objective of this study was to examine the neuronal density of the cingulate cortex area (CC) and amygdala in an animal model of colitis.

Materials and methods: In this experiment, 13 male Wistar rats were subjected to study. Colitis was induced in the rats by transrectally administering 1 cc of acetic acid 3% under sedation with xylazine 10% (5 mg/kg). After 14 days of colitis, the rats were euthanized under high doses of anesthesia with ketamine (50 mg/kg), xylazine (10 mg/kg), and diazepam (2.5 mg/kg). Their brains were then removed surgically. Six-micrometer-thick brain slices were stained with cresyl violet, and the neuronal density of the amygdala, area 1 of the cingulate cortex area (CC1), and area 2 of the cingulate cortex area (CC2) was assessed via microscopic imaging.

Results: The mean ± standard deviation (SD) of the neuronal density in CC1 was significantly decreased in rats with colitis compared to the control group in both the right CC1 (43.53 ± 9.63 vs. 62.7 ± 11.89; p-value ˂ 0.001), and left CC1 (41.19 ± 9.05 and 63.1 ± 7.44; p-value ˂ 0.001). Additionally, the neuronal density of CC2 in the colitis group was found to be significantly lower than that of the controls in both the right CC2 (57.8 ± 13.23 vs. 87.95 ± 8.76; p-value ˂ 0.001), and left CC2 (55.42 ± 11.3 vs. 98 ± 8.99; p-value ˂ 0.001). Furthermore, the amygdala had a lower neuronal density in both hemispheres in rats with colitis in comparison to the controls bilaterally: right hemisphere (24.51 ± 5.49 and 36.3 ± 7.44; p-value = 0.360), and left hemisphere (24.52 ± 5.53 VS. 35.25 ± 5.6; P-value = 0.869).

Conclusion: This study showed that colitis can reduce the neuronal density within cortical areas and amygdala of both hemispheres. Considering the cingulate cortex's role in suppressing pain perception, any harm inflicted upon this region of the brain can has the ability to impact the cognitive and sensory aspects of pain.