Effect of the σ
-receptor agonist (+)-pentazocine [(+)PTZ, 10 mg/kg, s.c] on the Phe-Phe amide (2 pmol, i.t.)-induced prolongation of the tail-flick latency in non-diabetic and diabetic mice. (+)PTZ was administered subcutaneously 30 min prior to the administration of Phe-Phe amide. Each column represents the mean with S.E.M. for 10 mice. *P < 0.05, ***P < 0.001 vs. respective before-treatment group; #P < 0.05, ###P < 0.001 vs. vehicle-pretreated group (Bonferroni test).