Infrared Thermography in Serotonin-Induced Itch Model in Rats

The study validated the application of infrared thermography in a serotonin-induced itch model in rats since the only available method in animal models of itch is the count of scratching bouts. Twenty four adult Sprague-Dawley male rats were used in 3 experiments: 1) local vasomotor response induced by intradermal serotonin (10 l) was evaluated against isotonic saline and Methysergide (10 l); 2) dose-temperature relation of intradermal serotonin with different concentrations (1%, 2%, 4%) at the site of injection was tested; 3) the local vasomotor responses in anaesthetized rats with no scratching reflex was investigated. Serotonin elicited significant scratching and lowered the local temperature at the site of injection. A negative dose-temperature relationship of serotonin was found by thermography. Vasoregulation at the site of serotonin injection took place in the absence of scratching reflexes. Thermography is a reliable, non-invasive, and objective method for assessment in serotonin-induced itch model in rat.