Mode of delivery alters sensitivity to thermal and chemical stimuli in adult rats: An experimental study

Background: The mode of delivery might prompt a long-lasting alteration in physiological and behavioral responsiveness in offspring. Objective: This study was intended to evaluate if the mode of delivery could alter sensitivity to thermal and chemical stimuli in female rats. Materials and Methods: 56 adult female Wistar rats (200–220 gr) that were born by vaginal or cesarean section (C-section) were used (n = 28/each). Inflammatory pain was induced by subcutaneous injection of formalin into the hind paw. The thermal nociceptive threshold was determined by tail-flick and hot plate tests. Besides, the Western blot test was used to evaluate the spinal cord levels of c-Fos and c-Jun proteins. Results: Formalin-induced inflammation was significantly decreased in C-section group as compared to vaginally born rats (p < 0.001). The baseline nociceptive threshed and morphine-induced analgesia were significantly increased in C-section groups in comparison to vaginally born rats. In addition, the levels of c-Fos and c-Jun proteins were significantly decreased in the spinal cord of C-section rats as compared to vaginally born animals (p < 0.01). Morphine treatment could decrease the expression of c-Fos and c-Jun in the C-section group (p < 0.05). Conclusion: Overall, C-section rats showed lower spinal nociceptive processing and neuronal activity later in life, compared to the vaginal born rats. Key words: Childbirth, C-section, Nociception, Inflammation, Rats.