Involvement of dopamine D2 receptors of the central amygdala on the acquisition and expression of morphine-induced place preference in rat.
In the present study, the effects of intra-central amygdala (CeA) injections of dopamine (DA) D2-like receptor agonist and antagonist on the acquisition and expression of morphine-induced place preference in male Wistar rats have been investigated. Subcutaneous administration of different doses of morphine sulphate (0.5-10 mg/kg) produced a dose-dependent conditioned place preference (CPP). Using a 3-day schedule of conditioning, it was found that the DA D2/D3 receptor agonist, quinpirole (0.3-3 microg/rat), or the DA D2 receptor antagonist, sulpiride (0.04-5 microg/rat), did not produce a significant place preference or place aversion. Intra-CeA administration of quinpirole (0.3 and 1 microg/rat) with an ineffective dose of morphine (0.5 mg/kg) elicited a significant CPP. On the other hand, quinpirole (0.3 microg/rat) injection into the CeA induced CPP in combination with the lower doses of morphine (0.5 and 2.5 mg/kg), but decreased the response of higher dose (7.5 mg/kg) of morphine. This response of quinpirole was attenuated by sulpiride (0.2 microg/rat). Sulpiride by itself (0.04-5 microg/rat) reduced the acquisition of morphine (7.5 mg/kg)-induced place preference. The administration of the higher dose of sulpiride (1 and 5 microg/rat) or the higher dose of quinpirole (3 microg/rat) during acquisition decreased the locomotor activity of the animals on the testing days. The injection of the low dose of quinpirole (0.3 microg/rat) on the test day reduced the expression of morphine-induced CPP, but the high dose of quinpirole (3 microg/rat) potentiated this expression. The administration of sulpiride (5 microg/rat) attenuated the quinpirole response. The injection of sulpiride (1 and 5 microg/rat) abolished the expression of morphine-induced CPP. It is concluded that the CeA DA D2-like receptors may play an active role in morphine reward.
Rezayof
Ameneh
A
Department of Biology, Faculty of Science, Tehran University, Tehran, Iran.
Zarrindast
Mohammad-Reza
MR
Sahraei
Hedayat
H
Haeri-Rohani
Ali-Haeri-Rohani
AH
D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000502:physiology*; D013469:Sulpiride / Q000494:pharmacology
D000701:Analgesics, Opioid; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D009020:Morphine; D013469:Sulpiride