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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Exp Clin Psychopharmacol. 2015 Aug 10;23(5):405–414. doi: 10.1037/pha0000042

Figure 4.

Figure 4

Effects of cumulative morphine on ICSS before and after repeated saline or morphine + IP acid. Figure 4A and 4B: repeated vehicle + acid group, Figure 4C and 4D: repeated 1.0 mg/kg/day morphine + acid group, Figure 4E and 4F: repeated 3.2 mg/kg/day morphine + acid group. Left column of panels (A,C,E) shows effects of morphine on ICSS expressed as Percent Pre-drug Baseline total stimulations delivered across all frequencies of brain stimulation. Abscissae: morphine dose in mg/kg. Ordinates: Percent Pre-drug Baseline total stimulations. Filled symbols represent ICSS rates that were statistically different from Daily Baseline, and asterisks represent ICSS rates that were statistically different across test days (Day 0 vs Day 7) as determined by two-way ANOVA followed by a Holm-Sidak post hoc test, P<0.05. Right column of panels (B,D,F) shows full ICSS frequency–rate curves on Day 7 for the Daily Baseline and after cumulative 3.2 mg/kg morphine. Abscissae: Frequency of electrical brain stimulation in Log Hz. Ordinate: Percent maximum control reinforcement rate (%MCR). Filled points represent frequencies at which reinforcement rates were statistically different from the Daily Baseline as determined by a two-way ANOVA followed by a Holm–Sidak post hoc test, P < 0.05. Statistical results are as follows: (A) significant effect of morphine dose [F(4, 24) = 41.9, P < 0.05], no effect of test day [F(1, 6) = 0.1, P > 0.05], and no interaction [F(4, 24) = .5, P>0.05]. (B) significant effect of morphine [F(4, 24) = 27.7, P<0.05] and frequency [F(9, 54) = 51.9, P < 0.05], and a significant interaction [F(36, 216) = 12.6, P < 0.05]. (C) significant effect of morphine dose [F(4, 24) = 48.5, P < 0.05] and test day [F(1, 6) = 9.9, P < 0.05], and a significant interaction [F(4, 24) = 4.9, P < 0.05]. (D) significant effect of morphine [F(4, 24) = 27.3, P < 0.05] and frequency [F(9, 54) = 36.9, P < 0.05], and a significant interaction [F(36, 216) = 5.1, P < 0.05]. (E) significant effect of morphine dose [F(4, 24) = 38.4, P < 0.05], no significant main effect of test day [F(1, 6) = 3.2, P > 0.05], but a significant interaction [F(4, 24) = 4.0, P < 0.05]. (F), significant main effect of morphine [F(4, 24) = 13.9, P < 0.05] and frequency [F(9, 54) = 58.7, P < 0.05] and a significant interaction [F(9, 54) = 7.5, P < 0.05]. Data show mean ± SEM for 7 rats.