Table 1. Relative effects of FR increases, IP acid, and SC morphine on social- vs. food-maintained responding.
For social self-administration, demand curves were determined for three door-open times (15, 30, and 60 sec), but effects of IP acid and analgesics were determined only for the 30-sec door open time. For food-maintained responding, the status of food restriction or free feeding is specified, and effects of IP and analgesics were determined only under free-feeding conditions. All data show mean values (95% CL) from 6 rats (3 female, 3 male).
| Demand Curves |
||||
|---|---|---|---|---|
| Reinforcement | FR 1 Baseline | Essential | IP Acid | Morphine |
| Conditions | # Reinforcers | Value | EC50 (%) | ED50 (mg/kg) |
| Social | ||||
| 15 s Door Open | 35.5 (24.6–46.4) | 5.1 (4.4–5.8) | ND | ND |
| 30 s Door Open | 26.3 (21.9–30.7) | 5.6 (4.9–6.3) | 0.42 (0.36–0.48) | 1.06 (0.70–1.63) |
| 60 s Door Open | 20.5 (15.4–25.6) | 7.0 (5.3–8.7) | ND | ND |
| Food | ||||
| Food Restricted | 53.2 (49.3–57.0)* | 15.2 (9.1–21.4)* | ND | ND |
| Free Fed | 53.2 (47.0–59.3)* | 10.8 (9.1–12.5)* | 2.40* (1.99–2.91) | 5.26* (4.05–6.68) |
Asterisk indicates that values for food reinforcement are significantly higher than all values for social reinforcement as determined by non-overlapping confidence limits.
ND-Not Determined. Individual α values were transformed to “essential value” such that a larger number reflects greater reinforcing effectiveness using the following equation (Hursh 2014):