title: Effects of ultra-low doses of nicotine on the expression of morphine-induced conditioned place preference in mice.
abstract: In the present study, the effects of acute administration of nicotine, as well as nicotinic and muscarinic acetylcholine receptor antagonists, on the expression of morphine-induced conditioned place preference, have been investigated in male Swiss-Webster mice. Animals received different doses of morphine 5 days after surgical cannulation in the lateral ventricle. Subcutaneous injections of morphine (2-5 mg/kg) in mouse produced place preference in a dose-dependent manner. Furthermore, both intraperitoneal (0.0006-0.1 mg/kg) and intracerebroventricular (0.007-25 ng) nicotine administration significantly reduced the expression of morphine-induced place preference, in a dose-dependent manner. Nicotine, however, was effective over narrow ultra-low dose ranges (0.0012, 0.0025, 0.005 and 0.01 mg/kg; intraperitoneal) and (0.03, 0.1, 0.3 and 0.6 ng/mouse; intracerebroventricular). In addition, locomotor activity was reduced when higher doses of nicotine [both intraperitoneal (0.02, 0.03 and 0.1 mg/kg) and intracerebroventricular (10 and 24 ng/mouse)] were used. Nicotine alone, however, did not cause motivational effects. Intracerebroventricular injection of hexamethonium (0.03, 0.1 and 0.3 mug/mouse; 10 min before nicotine) diminished the effects of nicotine on morphine-induced conditioned place preference. This effect could neither be obtained by intraperitoneal administration of hexamethonium (1, 5 and 10 mg/kg; 30 min before nicotine), nor be reproduced after either intracerebroventricular or intraperitoneal injection of atropine (a muscarinic receptor antagonist). The antagonists, themselves, did not show any motivational effects when used alone and were unable to affect the expression of morphine-induced conditioned place preference. It appears that ultra-low doses of nicotine can reduce the expression of morphine-induced place preference, and that central nicotinic acetylcholine receptors play a role in this regard.
authors.affiliation: Neuroscience Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Jamal
authors.initials: J
authors.lastname: Shams
authors.forename: Hedayat
authors.initials: H
authors.lastname: Sahraei
authors.forename: Azam
authors.initials: A
authors.lastname: Gholami
authors.forename: Ali
authors.initials: A
authors.lastname: Haeri-Rohani
authors.forename: Mahrooz
authors.initials: M
authors.lastname: Alaf-Javadi
authors.forename: Houri
authors.initials: H
authors.lastname: Sepehri
authors.forename: Seyed H
authors.initials: SH
authors.lastname: Salimi
authors.forename: Hassan
authors.initials: H
authors.lastname: Ghoshooni
mesh_terms: D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D018738:Hexamethonium / Q000494:pharmacology; D007276:Injections, Intraventricular; D007279:Injections, Subcutaneous; D008297:Male; D008568:Memory / Q000187:drug effects; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D009294:Narcotics / Q000494:pharmacology*; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects; D012054:Reinforcement, Psychology
chemical_list: D009294:Narcotics; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D018738:Hexamethonium; D009538:Nicotine; D009020:Morphine