Fig. 2

Effects of minocycline and dose responses to morphine on the hot plate. After habituation to the apparatus, n = 8 rats per sex were gavaged with 50 mg/kg minocycline, and n = 8 rats per sex were gavaged with an equal volume of water (1.25 ml/kg). Their latencies to respond to the painful stimulus of the hot plate were taken 10 h post gavage, and they were recorded twice 20 min apart and averaged as Baseline 1 (see “Methods” section for full details). Immediately following Baseline 1 measurements, rats were either gavaged with a second dose of minocycline (25 mg/kg) or equal volume of water a second time (1.25 ml/kg). One hour after the second gavage, latencies to respond to the stimulus on the hot plate were recorded twice and averaged to obtain Baseline 2 (a). The dose response curve following incremental doses of morphine (mg/kg) administration is graphed for rats in all groups. ED₅₀ is marked to represent the doses of morphine that elicit 50 % MPE (b). The ED₅₀ (mg/kg) doses of morphine for males and females treated with or without minocycline are graphed to show the values of morphine required to obtain 50 % MPE. Asterisk represents significant interaction of sex and minocycline treatment (p < 0.05); number sign represents main effect of sex (p < 0.001)