Effects of cysteamine on nociception in mice

AIM: The present study was carried to study the effects of cysteamine on no ciception in mice. METHODS: The pain assays were the hot plate and the tail flick test. RESULTS: When cysteamine, a drug well known as a somatostatin depletor, was administered 1 and 4 but not 24 h before the tests (hot plate , tail flick), the nociceptive threshold was elevated when the drug was adm inistered at high doses (50 and 100 mg/kg) while at a lower dose (10 mg/kg) , it was able to elevate the nociceptive threshold in the hot plate test on ly. In the hot plate as well the tail flick test cysteamine effects are rev ersed by naloxone administration and potentiated by morphine administration , whereas neither somatostatin nor cyclo-(7-aminoheptanoyl-Phe-D-Trp-Lys-Th r [Bzl], a reported somatostatin antagonist, changes cysteamine effects. CO NCLUSION: These results suggest that cysteamine effects on the nociceptive threshold in the hot plate and tail flick test may be mediated by cysteamin e interference with the opioid system.