ISSN:
1432-2072
Keywords:
Bromocriptine
;
Conditioned reward
;
D1 receptors
;
D2 receptors
;
Dopamine
;
Reinforcement
;
Reward
;
SCH 23390
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract It has been suggested that reward-related learning may require intact functioning at the dopamine D1 receptor. The present experiment tested this hypothesis by challenging the reward-enhancing effects of the D2 agonist, bromocriptine, with a D1 antagonist, SCH 23390. For comparison, the effects of the D2 antagonist, pimozide, were also evaluated. Male rats (n=240) were pre-exposed to a chamber with two levers, one producing a 3-s lights-off stimulus and the other a 3-s tone stimulus. Four conditioning sessions followed, during which levers were absent and presentations of the lights-off stimulus were paired with food. Testing consisted of comparing presses on each lever after conditioning to before conditioning for each rat. Control groups showed a significantly greater increase in responding for lights-off than tone, indicating that the lights-off stimulus had become a conditioned reward. Results showed that bromocriptine (0.25–10.0 mg/kg, IP, 60 min before test session) enhanced responding at doses of 2.5 and 5.0 mg/kg significantly more on the conditioned reward lever than on the other lever. The lowest dose of SCH 23390 (1.0 µg/kg, SC, 2 h before testing) eliminated the bromocriptine-produced enhancement at 2.5 mg/kg and a significant enhancement was seen at 10.0 mg/kg. The higher doses of SCH 23390 (5.0 and 10.0 µg/kg) eliminated the bromocriptine effect and the conditioned reward effect itself, respectively. The low dose of pimozide (0.1 mg/kg, IP, 4 h before test session) eliminated the bromocriptine-produced enhancement at 2.5 and 5.0 mg/kg and a significant enhancement was now seen at 10.0 mg/kg; the higher dose (0.2 mg/kg) appeared to block the conditioned reward effect itself. These results suggest that both SCH 23390 and pimozide interfered with the reward-enhancing effects of bromocriptine. Thus, the present results suggest that reward-related learning can be enhanced through D2 receptor stimulation with bromocriptine and that this effect appears to depend on intact D1 receptor function.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02245944
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