Fig. 6.
Systemic dermorphin [D-Arg2, Lys4] (1–4) amide (DALDA) reduces the evoked C-component of wide-dynamic range neurons to electrical stimulation in naive rats. (A) An analog recording of wide-dynamic range neuronal responses to an intracutaneous electrical stimulus (supra-C-fiber activation threshold, 2 ms) before and after systemic DALDA (10 mg/kg, intraperitoneal). Wide-dynamic range neuronal responses display A- and C-components to the test stimulus. (B) The stimulus-response (S-R) functions of the A- and C-components of wide-dynamic range neuronal response to graded intracutaneous electrical stimuli (0.1 to 5 mA, 2 ms) before and 30 to 45 min after systemic injection of vehicle (Veh; 15-min pretreatment) with DALDA (10 mg/kg, n = 6, intraperitoneal). (C) The total A- and C-component to graded electrical stimuli before and after systemic injection of vehicle with DALDA. (D) The S-R functions of the A-component and C-component before and after systemic injection of methylnaltrexone (MNTX; 5 mg/kg, intraperitoneal) with DALDA (10 mg/kg, n = 6, intraperitoneal). (E) The total A- and C-component to graded electrical stimuli before and after systemic injection of methylnaltrexone with DALDA. B, D: Two-way repeated measures ANOVA with Bonferroni post hoc test. C, E: Paired t test. Data are expressed as mean ± SD. *P < 0.05, **P < 0.01 versus predrug.