Validation of a porcine behavioural model of UVB induced inflammatory pain

Background and aim Cutaneous inflammation induced by ultraviolet B-light (UV-B) is considered a valuable translational pain model. Until now, the development of primary hyperalgesia has been assessed predominantly in rodents, whereas porcine skin might be advantageous due to its greater homology with human skin. The aim of the present study was to investigate porcine behavioural responses to nociceptive mechanical and thermal stimulations following UV-B inflammation. Methods One skin area of 4 cm2 in the flank of 16 male pigs of 55 ± 6 kg was irradiated by UV-B using 3xMED (Minimum Erythema Dose). Changes in pain sensitivity were assessed 24 and 48 h following irradiation via delivery of mechanical (Pressure Application Measurement device) and thermal (CO2 laser) stimulations to the inflamed skin area and to an untreated control site. Results All animals showed higher sensitivity in the inflamed skin site 24 and 48 h following irradiation, compared to the control site (P< 0.05). Pressure withdrawal threshold decreased in the inflamed site: 231 g (148-451) against 408g (347-684) after 24 hours and 200 g (106-293) against 656g (405-902) after 48 h. Similarly, latency to respond to the laser stimulus was lower at the inflamed site: 5 s (3-7) against 9 s (4-2) after 24h and 4 s (3-15) against 20 s (8-25) after 48 h. One and two days after irradiation, a tendency was found for an increased cutaneous mechanical pain sensitivity compared to baseline values in the site irradiated with UV-B light (P = 0.092). Thermal sensitivity was increased within the inflamed site 24 h after irradiation with latency changing from 17s (4-25) at baseline to 5 s (3-7) at 24 h (P =0.001). At 48 h, the response latency had not decreased any further (P = 0.414). Conclusions Our study shows that behavioural recordings are a valid tool for the assessment of mechanical and heat sensitization following UV-B inflammation in porcine skin.