Mode of Delivery Alters Dental Pulp Nociception and Pain-Induced Changes in Cognitive Performance in Adults' Male Rats

Can J Physiol Pharmacol. 2020 Jun 9. doi: 10.1139/cjpp-2019-0370. Online ahead of print.


This study examined the effects of delivery mode on the response to inflammatory pulpal pain and pain-induced changes in cognitive performance in adult rats. Experiments were done on rats born by vaginal or caesarean section (C-section) delivery. Dental pulp was irritated by intradental capsaicin (100 µg) application and then nociceptive scores were recorded for 40 min. Spatial and passive avoidance learning and memory were assessed using Morris Water Maze (MWM) and shuttle box tools, respectively. Additionally, in vivo recording of field excitatory postsynaptic potential (fEPSP) in the CA1 of the hippocampus, was used to verify synaptic plasticity. Capsaicin produced more significant nociceptive behaviour in vaginally delivered rats compared to C-section (P<0.01). C-section delivered rats show better performance in both MWM and shuttle box tests. Likewise, C-section rats had greater fEPSP slopes compared to the vaginally delivered group (P<0.05). Capsaicin impairs cognitive performance in rats born by each delivery route. However, capsaicin effects were more significant in rats delivered vaginally than by C-section. Overall, C-section delivered rats show lower sensitivity to capsaicin-evoked pulpal nociception and better cognitive performance than vaginally delivered rats. These effects are in part mediated by reduced neuroinflammation and enhanced neuronal synaptic plasticity following C-section delivery.