| The effects of MIF-1 and morphine on rats were studied in the conditioned place preference paradigm. A 4 X 4 factorial design was used, with 0.0, 0.1, 1.0, 10.0 mg/kg of MIF-1 and 0.0, 1.0, 5.0, 10.0 mg/kg of morphine sulfate. Three days of pre-conditioning were followed by 4 days of conditioning. The dependent variable was percent of seconds spent in drug-paired compartment minus seconds spent in vehicle-paired compartment on day 8. There were significant main effects for MIF-1 and for morphine. MIF-1 decreased place preference times and produced scores less than zero for all doses. Morphine increased conditioned place preference times for every dose. When doses of MIF-1 and morphine were combined, the net effect seemed to be that associated with the compound with the greater dose, or morphine if the doses were equal. Accordingly, MIF-1 demonstrated a significant negative effect in this paradigm when paired with diluent, and decreased latencies when paired with morphine. |
