title: Dorsal hippocampal muscarinic and nicotinic receptors are involved in mediating morphine reward.
abstract: In the present study, the effects of bilateral injections of cholinergic agents into the hippocampal CA1 region on morphine-induced conditioned place preference (CPP) were investigated in male Wistar rats. Subcutaneous (s.c.) administration of different doses of morphine sulphate (0.5-6 mg/kg) produced a dose-dependent CPP. Using a 3-day schedule of conditioning, it was found that intra-CA1 administration of the anticholinesterase, physostigmine (2, 4 and 8 microg/rat) significantly potentiated the morphine (0.5 mg/kg)-induced CPP. Moreover, intra-CA1 administration of the muscarinic receptor antagonist, atropine (1, 4 and 7 microg/rat) inhibited the morphine (6 mg/kg)-induced CPP dose-dependently. On the other hand, atropine (7 microg/rat, intra-CA1) reversed the physostigmine-induced potentiation of the morphine response. Furthermore, intra-CA1 administration of nicotine (0.5, 0.75 and 1 microg/rat) with an ineffective dose of morphine (0.5 mg/kg) elicited a significant CPP. Bilateral injections of different doses of the nicotinic receptor antagonist, mecamylamine (2, 4 and 8 microg/rat) into the CA1 regions significantly inhibited the morphine (6 mg/kg)-induced CPP. Moreover mecamylamine (8 microg/rat, intra-CA1) decreased the effect of nicotine-induced potentiation of the morphine response. Intra-CA1 injections of physostigmine, atropine, nicotine or mecamylamine alone did not induce a significant place preference or place aversion. It may be concluded that the muscarinic and nicotinic receptors of the hippocampal CA1 regions play an important role in morphine reward.
authors.affiliation: Department of Biology, Faculty of Science, Tehran University, Tehran, Iran.
authors.forename: Ameneh
authors.initials: A
authors.lastname: Rezayof
authors.forename: Hengameh
authors.initials: H
authors.lastname: Zatali
authors.forename: Ali
authors.initials: A
authors.lastname: Haeri-Rohani
authors.forename: Mohammad-Reza
authors.initials: MR
authors.lastname: Zarrindast
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001522:Behavior, Animal; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003216:Conditioning, Operant / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009020:Morphine / Q000008:administration & dosage*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000008:administration & dosage*; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000502:physiology*; D012201:Reward
chemical_list: D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D009294:Narcotics; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D008464:Mecamylamine; D009538:Nicotine; D009020:Morphine; D001285:Atropine; D010830:Physostigmine