METHADONE-INDUCED ATTENUATION OF THE EFFECTS OF DELTA-9 TETRAHYDROCANNABINOL ON TEMPORAL DISCRIMINATION IN PIGEONS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 213  (2) , 247-253
Abstract
Pigeons responded under a discrete trial procedure in which they were required to peck 1 of 2 keys depending on the duration of a conditional stimulus (general illumination of the experimental chamber). Correct choices (red key after a 4 s stimulus; green key after an 8 s stimulus) caused the intermittent presentation of food; incorrect choices caused a darkened chamber. Intermediate durations (probe stimuli) were presented occasionally. The effects of tetrahydrocannabinol (THC; 0.06-0.50 mg/kg) and repeated methadone injections (2-20 mg/kg per day) were assessed alone and in combination. THC caused a dose-dependent decrease in accuracy with the greater effect on long-duration trials. Repeated methadone alone caused a decrease in accuracy only when the methadone dose was changed. High doses of methadone (6 and 20 mg/kg per day) caused a complete (0.25 mg/kg of THC) or partial (0.50 mg/kg of THC) attenuation of effects of THC on temporal discirimination accuracy as compared to a low methadone dose (2 mg/kg per day) or THC alone. The results suggest the possibility of cross-tolerance or antagonism between methadone and THC.