Figure 3. Naloxone does not block loperamide effects on mechanosensitivity of C-fibers.

A) Naloxone pretreatment does not prevent the loperamide (5 µg/10 µl) – induced increase in mechanical thresholds of C-fibers. Naloxone was used either in a small (4 µg in 10 µl, n = 3) or a high dose (80 µg in 20 µl, n = 10). Medians and 25th percentile data are shown. 75th percentiles were identical to median value. (**p<0.01, Wilcoxon matched pairs, n = 13). B) Loperamide –induced decrease in response to suprathreshold mechanical stimulation, is not prevented by naloxone pretreatment. Loperamide and naloxone doses are identical to those used in A. Medians, 25th percentile and 75th percentiles are shown. (**p<0.01, Wilcoxon matched pairs).