title: Involvement of GABA(B) receptors of the dorsal hippocampus on the acquisition and expression of morphine-induced place preference in rats.
abstract: In the present study, effects of intra-hippocampal CA1 (intra-CA1) injections of GABA(B) 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 (0.5-6 mg/kg) produced a dose-dependent conditioned place preference (CPP). Using a 3-day schedule of conditioning, it was found that the GABA(B) receptor agonist, baclofen (0.5-2 microg/rat; intra-CA1), or the GABA(B) receptor antagonist, phaclofen (1-3 microg/rat; intra-CA1), did not produce a significant place preference or place aversion. Intra-CA1 administration of baclofen (1 and 2 microg/rat; intra-CA1) decreased the acquisition of CPP induced by morphine (3 mg/kg; s.c.). On the other hand, intra-CA1 injection of phaclofen (1 and 2 microg/rat; intra-CA1) in combination with a lower dose of morphine (1 mg/kg) elicited a significant CPP. The response of baclofen (2 microg/rat; intra-CA1) was reversed by phaclofen (4 and 6 microg/rat; intra-CA1). Furthermore, intra-CA1 administration of baclofen but not phaclofen before testing significantly decreased the expression of morphine (3 mg/kg; s.c.)-induced place preference. Baclofen or phaclofen injections had no effects on locomotor activity on the testing sessions. It is concluded that the GABA(B) receptors in dorsal hippocampus may play an active role in morphine reward.
authors.affiliation: Department of Pharmacology and Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran. zarinmr@ams.ac.ir
authors.forename: Mohammad-Reza
authors.initials: MR
authors.lastname: Zarrindast
authors.forename: Roohollah
authors.initials: R
authors.lastname: Massoudi
authors.forename: Houri
authors.initials: H
authors.lastname: Sepehri
authors.forename: Ameneh
authors.initials: A
authors.lastname: Rezayof
mesh_terms: D000818:Animals; D001245:Association Learning / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000378:metabolism*; D012054:Reinforcement, Psychology
chemical_list: D058786:GABA-B Receptor Agonists; D058788:GABA-B Receptor Antagonists; D009294:Narcotics; D018080:Receptors, GABA-B; D009020:Morphine