Abstract
The equipment described was developed to permit the comparison of the effects of periaqueductal grey stimulation on a nociceptive reflex evoked by thermal stimulation of the face with its effects on the responses of sensory neurones in the trigeminal nucleus caudalis to noxious thermal stimuli applied to the same facial regions. It comprises an implanted stimulating electrode system and a feedback controlled thermal stimulating device. A detailed description of this device including the control circuitry is given. Typical results (for control values of nociceptive threshold) are given and these compare favourably with other tests of nociceptive behaviour. This face heating device offers a greater degree of control of the stimulus parameters than other methods of applying noxious stimuli to unrestrained rats and is suitable for use in studies of analgesic drug action, although it is more complex and time consuming to apply than other commonly used nociceptive threshold tests such as the tail flick.