1. Psychostimulant Drugs Potentiate Morphine Analgesia in the Formalin Test 
Suntanu Dalal, MSc, Ronald Melzack, PhD 
Journal of Pain and Symptom Management 
Volume 16, Issue 4, Pages (October 1998)
DOI: /S (98)

2. Fig. 1
Experiment 1, Drug Administration Time 1. Time course of mean formalin pain ratings for rats given morphine at −30 min and methylphenidate at −20 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 1A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines of the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

3. Fig. 1
Experiment 1, Drug Administration Time 1. Time course of mean formalin pain ratings for rats given morphine at −30 min and methylphenidate at −20 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 1A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines of the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

4. Fig. 2
Experiment 1, Drug Administration Time 2. Time course of mean formalin pain ratings for rats given morphine at -10 min and methylphenidate at 0 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 2A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines on the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

5. Fig. 2
Experiment 1, Drug Administration Time 2. Time course of mean formalin pain ratings for rats given morphine at -10 min and methylphenidate at 0 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 2A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines on the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

6. Fig. 3
Experiment 2, Drug Administration Time 1. Time course of mean formalin pain ratings for rats given morphine at −30 min and d-amphetamine at −20 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 3A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines on the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

7. Fig. 3
Experiment 2, Drug Administration Time 1. Time course of mean formalin pain ratings for rats given morphine at −30 min and d-amphetamine at −20 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late-phase data from Figures 3A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines on the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

8. Fig. 4
Experiment 2, Drug Administration Time 2. Time course of mean formalin pain ratings for rats given morphine at −10 min and d-amphetamine at 0 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late phase data from Figures 4A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines of the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )

9. Fig. 4
Experiment 2, Drug Administration Time 2. Time course of mean formalin pain ratings for rats given morphine at −10 min and d-amphetamine at 0 min: (A) is the “saline control for morphine injection,” in (B) morphine is held constant at 1.0 mg/kg, and in (C) morphine is held constant at 2.5 mg/kg. (D) summarizes the late phase data from Figures 4A–C by averaging each group over 30 min for the period t = +20 min to t = +50 min. The vertical lines of the graphs represent the standard errors of the mean. Significant Mann-Whitney U’s, one-tailed, are indicated by * (P < 0.05) and ** (P < 0.01)
Journal of Pain and Symptom Management  , DOI: ( /S (98) )