TY - JOUR
T1 - Differential effects of two cannabinoid recepter agonists on progressive ratio responding for food and free-feeding in rats
AU - Higgs, Suzanne
AU - Barber, David
AU - Cooper, Alison
AU - Terry, Philip
PY - 2005/9/1
Y1 - 2005/9/1
N2 - The cannabinoid receptor agonists Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and HU-210 were compared in terms of their effects on: (1) progressive ratio (PR) responding for food, and (2) free food intake. In the first experiment, food-deprived Wistar rats were trained on a time-constrained (60 min) PR-5 schedule for food reinforcement, in which the response requirement incremented by five lever presses for each successive reinforcer. One group of rats received vehicle, 0.5, 1 or 3 mg/kg Delta(9)-THC (i.p.), and three other groups received HU-210 (i.p.) at three different dose ranges, spanning 0.001 - 0.1 mg/kg. In the second experiment, the effects of the two drugs on free food intake were tested in a separate group of non-deprived rats. For PR responding, Delta(9)-THC significantly increased the break point (final ratio completed) and the total number of lever presses emitted. The same drug also significantly increased free food intake. However, the effects of HU-210 were quite different: it did not alter PR responding at any dose; instead, its only significant effect was to reduce free food intake at 0.06 mg/kg. These data suggest that increased motivation to obtain food might underlie the hyperphagic effects of Delta(9)-THC. However, the synthetic agonist HU-210 has different effects: it only acts to reduce feeding behaviour, an outcome that probably reflects non-specific behavioural disruption. These findings suggest important differences between the two CB1 receptor agonists in terms of their pharmacological effects.
AB - The cannabinoid receptor agonists Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and HU-210 were compared in terms of their effects on: (1) progressive ratio (PR) responding for food, and (2) free food intake. In the first experiment, food-deprived Wistar rats were trained on a time-constrained (60 min) PR-5 schedule for food reinforcement, in which the response requirement incremented by five lever presses for each successive reinforcer. One group of rats received vehicle, 0.5, 1 or 3 mg/kg Delta(9)-THC (i.p.), and three other groups received HU-210 (i.p.) at three different dose ranges, spanning 0.001 - 0.1 mg/kg. In the second experiment, the effects of the two drugs on free food intake were tested in a separate group of non-deprived rats. For PR responding, Delta(9)-THC significantly increased the break point (final ratio completed) and the total number of lever presses emitted. The same drug also significantly increased free food intake. However, the effects of HU-210 were quite different: it did not alter PR responding at any dose; instead, its only significant effect was to reduce free food intake at 0.06 mg/kg. These data suggest that increased motivation to obtain food might underlie the hyperphagic effects of Delta(9)-THC. However, the synthetic agonist HU-210 has different effects: it only acts to reduce feeding behaviour, an outcome that probably reflects non-specific behavioural disruption. These findings suggest important differences between the two CB1 receptor agonists in terms of their pharmacological effects.
KW - cannabis
KW - cannabinoids
KW - Delta(9)-tetrahydrocannabinol
KW - feeding
KW - HU-210
KW - eating
KW - operant responding
KW - rat
KW - progressive ratio schedule
UR - http://www.scopus.com/inward/record.url?scp=26044452409&partnerID=8YFLogxK
U2 - 10.1097/00008877-200509000-00011
DO - 10.1097/00008877-200509000-00011
M3 - Article
C2 - 16148443
VL - 16
SP - 389
EP - 393
JO - Behavioural Pharmacology
JF - Behavioural Pharmacology
ER -