Abstract
Intensive thermal stimulation of various skin areas is one of the most common behavioral pain-measurement methods used either in humans or in experimental animals. In tail-flick test, the thermal stimulation is focused on the dorsal surface of the tail in restrained animal, while in the plantar test, the stimulation is focused on the foot planta through a glass table in freely moving rats.
We modified the tail-flick test in the way that the tail withdrawal latency was measured in freely moving rats using plantar test apparatus. The aim of the experiment was to compare tail withdrawal latency measured by normal and modified tail-flick.
The latencies were measured in intact animals, in animals under analgesia (baclofen 5 mg/kg i.p.) and under hyperalgesia (capsaicin induced acute inflammatory pain, paw-incision induced surgical pain). The modified tail flick was tested on two frequently used intensities of the stimulation.
It was shown that in intact animals the tail flick latency did not correspond with those of any intensity of the modified tail-flick test, it lied between them. Under analgesia, the withdrawal latencies significantly increased and tail-flick latencies corresponded with those of the lower intensity of the modified tail-flick test.
Hyperalgesia models did not affect latencies of any method. It is concluded that modified tail-flick test can be used to measure analgesic effects of drugs and it may replace conventional tail flick test.