Restrictions on the interpretation of spinal reflex modulation in pain and analgesia research

The use of motor reactions including spinal motor mechanisms, such as tail-flick, hot plate test, and flexion reflexes, in research on pain and analgesia requires some precautions, and results should be interpreted with caution. Nocifensive specificity and analgesic selectivity cannot be established unequivocally by only comparing reflexes evoked by noxious stimuli with monosynaptic reflexes. Rather, it is necessary to compare the responses evoked by activating nociceptive and non-nociceptive flexor reflex afferent pathways and non-flexor reflex afferent pathways, preferably from different areas, if the effectiveness and selectivity of analgesic drugs or procedures are to be accurately assessed. In addition, monosynaptic reflexes to flexor and extensor muscles should be evaluated. This is of particular importance in animal experiments.