The formalin test : effects of different injection sites on the pattern of nociceptive responses

ABSTRACT

The formalin test is widely believed to provide a more valid model for clinical pain than tests with phasic mechanical or thermal stimuli. However; the different implementations of the test in use pose the possibility of confounding results. This study evaluated the effects of different injection sites on the pattern of nociceptive responses. The responses to forepaw injection was found to be significantly higher than that of hind paw injection in the first phase while the response to plantar injection was found to be significantly higher than that of dorsal injection. We conclude that the choice of injection site has some effects on the pattern of nociceptive responses