An animal model of hypnotic pain attenuation

The tonic immobility state (TIS) in rabbit has great potential as an animal model of hypnosis in humans, due to the strong similarities between TIS and hypnosis. It is additionally the only mammalian model available for studying mechanisms of hypnosis. However, its ability to modulate pain perception has yet to be clearly determined. The present experiment examined the effect of nociceptive conditioning in normal, TIS and lidocaine-treated rabbits. This involved three separate phases. In phase one all animals were trained on a continuous performance test (CPT). In the second phase animals were given Pavlovian conditioning to an auditory CS paired with a nociceptive US. In the third phase the animals are given a sensory recognition test. The control group were conditioned during a normal state, the TIS group were conditioned during TIS, the pain control animals were conditioned after lidocaine injection in the skin area stimulated by the nociceptive US. All animals in the normal group showed the greatest amount of pain conditioning, with an average disruption time (dt) of 175s. Animals in the lidocaine group showed little signs of conditioning with an average dt of 16s. Animals conditioned during TIS had an average dt of 42s. These results show that TIS can modulate pain perception similar to animals that did not experience a pain CS. They additionally argue that tonic immobility can produce attenuation of pain perception similar to hypnosis in humans.