Microinjections of flupenthixol into the caudate putamen of rats produce intrasession declines in food-rewarded operant responding.
Results of recent studies suggest that dopamine (DA) transmission in the caudate putamen may be involved in food reward-related learning. The purpose of the present study was to evaluate the contribution of DA terminals in the dorsal caudate putamen to food-rewarded operant responding. Experiment 1, a study measuring circling behaviour in 18 rats receiving systemic amphetamine (1.5 mg/kg) and unilateral intracaudate putamen injections of cis-flupenthixol (0.0, 1.0, 10.0, and 25.0 micrograms in 0.5 microliters), a DA receptor antagonist, or its pharmacologically inactive isomer trans-flupenthixol (25.0 micrograms in 0.5 microliter), determined a behaviourally effective dose of cis-flupenthixol. Results showed that cis-flupenthixol dose dependently increased ipsiversive turning and trans-flupenthixol did not. In Experiment 2, an operant study, 36 rats were trained to press a lever for food on a variable interval 30-s schedule. Rats were then randomly assigned to four groups, three of which received one of the following bilateral intracaudate injections prior to three subsequent test sessions: saline (n = 6; 0.5 microliters), cis-flupenthixol (n = 10; 25.0 micrograms/0.5 microliter), and trans-flupenthixol (n = 10; 25.0 micrograms/0.5 microliters). Rats in the home cage control group (n = 10) received two bilateral intracaudate putamen injections of cis-flupenthixol (25.0 micrograms/0.5 microliters) in their home cages and a final injection of cis-flupenthixol prior to a test session. The results showed that cis-flupenthixol, but not trans-flupenthixol or saline, produced a time-dependent intrasession decline in operant responding. This pattern resembled that seen in extinction.(ABSTRACT TRUNCATED AT 250 WORDS)
Beninger
R J
RJ
Department of Psychology, Queen's University, Kingston, Ontario, Canada.
D'Amico
C M
CM
Ranaldi
R
R
D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects* / Q000502:physiology; D003216:Conditioning, Operant / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005475:Flupenthixol / Q000008:administration & dosage / Q000494:pharmacology*; D005502:Food; D008297:Male; D008845:Microinjections; D011699:Putamen / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012201:Reward
D005475:Flupenthixol