Effect of chronic stress on capsaicin-induced dental nociception in a model of pulpitis in rats.

OBJECTIVE: Chronic stress can alter nociceptive sensitivity. However, the effect of stress exposure on dental nociception has been less addressed. Therefore, the present study investigated the effects of chronic exposures to some social and psychological stresses on pulpal nociceptive responses.

DESIGN: The stress groups were constructed as follows: forced swimming (n=6), restraint (n=6), and mild (n=10) and severe (n=15) crowding stresses. Rats were subjected to stress for 1h per day for a week. At the end of the stress session, pulp irritation was induced by intradental application of capsaicin (100μg). There were another capsaicin or capsaicin plus stress training groups that received articaine 5min before the administration of capsaicin. Nociceptive responses were recorded for 40min. The time (ins) of continuous shaking of the lower jaw and excessive grooming and rubbing of the mouth near the procedure site was measured as nociceptive behaviors. Data was analyzed using one-way analysis of variance (ANOVA) followed by post hoc Tukey's test.

RESULTS: Significant nociceptive responses were evoked by the administration of capsaicin. Exposures to forced swimming (p<0.01), restraint (p<0.001), and both mild and severe crowding stresses (p<0.05) exaggerated capsaicin-induced nociceptive reaction. There was, however, no significant difference in nociceptive reaction time between the different stress groups. Articaine buccal infiltration attenuated nociceptive time in capsaicin and capsaicin plus stress training groups (p<0.001).

CONCLUSIONS: The current data support the association between chronic stress exposures and nociceptive behavior following intradental capsaicin administration.