TABLE 2.
Mean (± S.E.M.) rates of responding under the FR30 stimulus-shock termination schedule (n=3-4) after administration of the DA D1-like agonist (SKF82958) and antagonist (SCH23390), DA D2-like antagonist (haloperidol), and opioid agonist (morphine) and antagonist (naltrexone) before and during chronic exposure to the cannabinoid CB1 receptor agonist AM411 (1.0 mg/kg per day, i.m.)
Control values (± S.D.) before and during chronic treatment are also given for comparison.
| Drug | Dose | Control Response Rate (S.E.M.) |
||
|---|---|---|---|---|
| Prechronic | Chronic | |||
| mg/kg | % | % | ||
| Control | Vehicle | 0 | 100.90 (±5.78 S.D.) | 100.00 (±7.59 S.D.) |
| DA D1 agonist | SKF82958 | 0.032 | 121.41 (±9.48) | 98.22 (±27.18) |
| 0.1 | 51.95 (±26.81) | 35.81 (±17.99) | ||
| 0.32 | 26.95 (±26.95) | 8.99 (±8.99) | ||
| 1.0 | 0 (±0) | 0.70 (±0.70) | ||
| DA D1 antagonist | SCH23390 | 0.01 | 100.37 (±22.18) | 101.86 (±24.42) |
| 0.032 | 9.88 (±7.84) | 36.51 (±18.77) | ||
| 0.1 | – | 28.60 (±28.14) | ||
| DA D2 antagonist | Haloperidol | 0.0032 | 99.55 (±10.03) | 93.18 (±13.07) |
| 0.01 | 91.09 (±10.99) | 77.44 (±7.44) | ||
| 0.032 | 83.23 (±17.91) | 61.16 (±14.31) | ||
| 0.1 | 0.30 (±0.21) | 26.36 (±24.03) | ||
| 0.32 | – | 0.16 (±0.16) | ||
| Opioid agonist | Morphine | 0.032 | 107.78 (±19.57) | – |
| 0.1 | 96.41 (±22.06) | 107.01 (±16.89) | ||
| 0.32 | 100.15 (±23.99) | 94.74 (±14.97) | ||
| 1.0 | 67.81 (±24.53) | 89.33 (±24.36) | ||
| 1.8 | 40.62 (±15.0) | – | ||
| 3.2 | 17.22 (±17.22) | 51.63 (±18.25) | ||
| 10.0 | – | 14.19 (±5.96) | ||
| Opioid antagonist | Naltrexone | 1.0 | 121.93 (±24.24) | 111.09 (±19.82) |
| 3.2 | 100.90 (±39.18) | 96.20 (±23.83) | ||
| 10.0 | 114.97 (±22.79) | 100.78 (±22.43) | ||
DA, dopamine; FR30, 30-response fixed ratio.