Rats received i.p. injections of saline (saline-saline control) or morphine (5mg/kg/injection; morphine-saline group) twice daily, for 6 days concurrent with i.th. injections of saline. The saline- L-732,138 and morphine− L-732,138 groups have received i.th. L-732,138 (20 μg/5 μl) injections concurrent with i.p. saline or morphine, respectively. In the Saline-TY027 group, the animals received repeated i.th. injections of a bivalent opioid agonist/Tachykinin NK1 receptor antagonist compound, TY027 (20 μg/5 μl/injection) twice daily for 6 days concurrent with i.p. saline injections. Thermal (A) and tactile (B) sensitivity of the animals was assessed prior to drug administration (naïve basal values - dotted lines) and 96 h after the last drug administration (bars).