Figure 4. Time-course changes in root mean square (RMS) and mean power frequency (MPF) values of electromyographic signals recorded from the sacrococcygeus dorsi lateralis muscle before (C) and 20 min after pretreatment (T) with intrathecally administered AP5 (75 or 150 nmol), followed by bilateral microinjection of 2.5 micro gram fentanyl into the locus ceruleus. Data on the aCSF pretreatment group from Figure 1are duplicated for comparison. Values presented are mean +/- SD, n = 6–8 animals per group. (dagger) P < 0.05 versus the corresponding baseline group in the Dunnett test. *P < 0.05 versus the aCSF group at comparable postfentanyl time points in the Scheffe test.