Discriminitive stimulus effects of endomorphin (EM) analogs in male rats trained to discriminate morphine injections from saline
Values represent the % maximum morphine-appropriate responding, ED50 [milligrams per kilogram, i.v. (S.E.M.)] after bolus injections made between sessions, or cumulative injections made within a single session. Response-rate impairment with the highest dose tested (5.6 mg/kg) as a percent of vehicle responding and S.E.M. of five to six rats/group.
| Bolus Injections | Cumulative Injections | |||
|---|---|---|---|---|
| Drug | Maximum % Drug-Appropriate Responding | ED50 | Maximum % Drug-Appropriate Responding | ED50 |
| Morphine | 100 | 0.879 (0.365) | 100 | 0.701 (0.046) |
| ZH850 | 97.2 | 2.320 (0.328) | 98.2 | 1.201 (0.170) |
| ZH831 | 98.0 | 1.631 (0.205) | 100 | 0.830 (0.131) |
| ZH853 | 94.9 | 2.104 (0.283) | 89.0 | 1.765 (2.333) |
| Response-rate impairment % | Response-rate impairment S.E.M. | Response-rate impairment % | Response-rate impairment S.E.M. | |
| Morphine | 77.1 | 11.6 | 54.5 | 19.1 |
| ZH850 | 30.4 | 11.4 | −0.3 | 11.7 |
| ZH831 | 21.1 | 8.8 | 30.6 | 27.0 |
| ZH853 | 15.1 | 10.2 | 0.8 | 2.8 |