Animal | 0.5 mA α-chloralose | 1.0 mA α-chloralose | 1.5 mA α-chloralose | 2.0 mA α-chloralose | 2.0 mA α-chloralose plus morphine | 2.0 mA α-chloralose plus morphine plus naloxone | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
β estimate | Cluster volume | β estimate | Cluster volume | β estimate | Cluster volume | β estimate | Cluster volume | β estimate | Cluster volume | β estimate | Cluster volume | |
1 | 0.22 | 0 | 1.95 | 2.46 | 1.74 | 2.05 | 1.80 | 2.26 | ||||
2 | 0.07 | 0 | 3.17 | 8.00 | 2.34 | 5.33 | 3.67 | 6.15 | ||||
3 | 2.63 | 0.62 | 2.64 | 1.64 | 0.51 | 0 | ||||||
4 | 2.09 | 1.43 | 2.45 | 0.62 | 1.37 | 0.82 | ||||||
5 | 0.82 | 0 | 3.04 | 0.62 | 2.46 | 0 | ||||||
6 | 0.61 | 0 | 5.12 | 5.33 | 3.97 | 3.69 | 5.26 | 3.49 | ||||
7 | 1.01 | 0 | 3.74 | 4.31 | 1.65 | 0.82 | 1.65 | 1.44 | ||||
8 | 1.24 | 0 | 4.02 | 5.13 | 2.47 | 1.64 | 2.02 | 0.82 | ||||
9 | 1.29 | 0 | 5.35 | 2.46 | 4.08 | 1.44 | ||||||
10 | 0.62 | 0 | 5.30 | 0.21 | 4.13 | 0 | ||||||
11 | 7.40 | 15.6 | 5.41 | 10.1 | 6.66 | 16.2 | ||||||
12 | 2.64 | 1.23 | 0.73 | 0.41 | 1.40 | 1.23 | ||||||
13 | 3.93 | 7.79 | 0.80 | 5.54 | 2.53 | 8.61 | ||||||
14 | 0.44 | 0 | 1.81 | 2.87 | 3.93 | 3.69 | 3.48 | 2.46 | 4.82 | 3.90 | ||
Mean | 0.24 | 0 | 0.93 | 0 | 2.18 | 1.64 | 3.91 | 4.22 | 2.51 | 2.45 | 3.31 | 4.90 |
SEM | 0.11 | 0 | 0.11 | 0 | 0.24 | 0.66 | 0.39 | 1.11 | 0.40 | 0.76 | 0.63 | 1.65 |
β estimate and cluster volume of the fMRI signal measured in the lumbar spinal cord in the slice with maximal intensity for animals 1–14. Electric stimulation of the hindlimb was performed using 0.5, 1.0, 1.5, or 2.0 mA current pulses. A block design with three conditions (alternating 2 different current levels and rest periods) was used in rats 1–10. A block design with two conditions (alternating a single current level with rest periods) was used for rats 11–14. Rat 14 underwent 0.5, 1.5, and 2.0 mA stimulation with a block design with two conditions to generate Figure 2. All animals were investigated under α-chloralose anesthesia. Effects of morphine were assessed beginning 10 minutes after intravenous injection of morphine in a dose of 10 mg/kg. Naloxone effects were assessed in the consecutive session and 5 minutes after the injection of naloxone in a dose of 4 mg/kg.