The genetic characteristics of the analgesic action of substance P, bradykinin and thyroliberin in the rats of 2 inbred strains

A participation of nonopiate peptide brain systems in the mechanism of individual pain sensation was studied. The experiments were carried out on rats of two inbred strains, Fischer-344 and WAG/G, which exhibit different threshold of thermal pain sensation. The action of nonopiate oligopeptides (substance P, bradykinin, and thiroliberin) on the latent period of tail immersion from hot water was studied. It was found that significant analgesic action of substance P, bradykinin, and thiroliberin is more pronounced in rats more sensitive to thermal stimuli (WAG/G). The rats with reduced thermal sensitivity (Fischer-344) are shown to be insensitive to analgesic action of substance P, bradykinin, and thiroliberin.