THE NK2 RECEPTOR ANTAGONIST SR48968 INHIBITS THALAMIC RESPONSES EVOKED BY THERMAL BUT NOT MECHANICAL NOCICEPTION

Extracellular recordings were made in the thalamic posterior nuclear g roup of anesthetized rats to study the effects of SR48968, a non-pepti de NK2 receptor antagonist, on the responses evoked by thermal or mech anical nociceptive cutaneous stimulation. SR48968 (0.125-0.5 mg/kg, i. v. route) inhibited the responses to thermal stimulation while being i neffective on mechanically evoked responses in doses up to 2 mg/kg i.v . This effect was stereoselective since SR48965, the (R) enantiomer of SR48968 with a 2000-fold lower affinity for NK2 receptors, did not mo dify thermally evoked responses at a dose of 1 mg/kg i.v. These result s support the notion that NK2 receptors are involved in thermal nocice ption.