A reliable, facial nociception device for unrestrained, awake animals: Effects of morphine and trigeminal complex lesions

A new technique is described for quantifying orofacial pain in unrestrained, freely moving animals. The key dependent variable is latency to a face-rubbing response executed with any paw. The response is elicited by heating a tiny resistor in contact with facial skin. The latency variability is significantly less than that of hot-plate/paw-lick and other measures. The measure precisely indexes effects of morphine, trigeminal complex lesions, and heat rate manipulations. For these reasons, the technique is potentially useful to all pain and analgesia researchers. Utilization of the face as site of nociceptive stimulation has special relevance for trigeminal studies.