Nociceptive responses to thermal and mechanical stimulations in awake pigs

Background Porcine skin exhibits a high degree of homology to human skin, and the pig has recently been used as a cutaneous pain model. However, before the full potential of this novel in vivo cutaneous pain model can be achieved, several methodological aspects related to the management of awake animal studies in a large species require further examination. This manuscript describes the initial development of a porcine model of cutaneous nociception and focuses on interactions between the sensory modality, body size and the anatomical location of the stimulation site. Methods Pigs of different body sizes (30 and 60 kg) were exposed to thermal (CO2 laser) and mechanical (pressure application measurement device) stimulations to the flank and the hind legs in a balanced order. The median response latency and the type of behavioural response were recorded. Results Small pigs exhibited significantly lower pain thresholds (shorter latency to response) than large pigs to thermal and mechanical stimulations. Stimulations at the two anatomical locations elicited very distinct sets of behavioural responses, with different levels of sensitivity between the flank and the hind legs. Furthermore, small animals exhibited lower levels of individual variability between single stimulations. Conclusions Our data indicate that this experimental approach may be valuable for use in studies that focus on porcine cutaneous nociception.