α7 Nicotinic acetylcholine receptors in the central amygdaloid nucleus alter naloxone-induced withdrawal following a single exposure to morphine

• Published in: Psychopharmacologia 2011-04, Vol.214 (4), p.923-931
• Main Authors: Ishida, Shigeru, Kawasaki, Yoichi, Araki, Hiroaki, Asanuma, Masato, Matsunaga, Hisashi, Sendo, Toshiaki, Kawasaki, Hiromu, Gomita, Yutaka, Kitamura, Yoshihisa
• Format: Article
• Language: English
• Subjects: Accountants; alpha7 Nicotinic Acetylcholine Receptor; Amygdala - drug effects; Amygdala - metabolism; Animals; Behavior, Animal - drug effects; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Brain; Conditioning (Psychology) - drug effects; Dose-Response Relationship, Drug; Male; Medical sciences; Microinjections; Morphine; Morphine - adverse effects; Naloxone; Naloxone - pharmacology; Neurosciences; Nicotinic Agonists - pharmacology; Nicotinic Agonists - therapeutic use; Nicotinic Antagonists - pharmacology; Nicotinic Antagonists - therapeutic use; Original Investigation; Pharmacology/Toxicology; Proto-Oncogene Proteins c-fos - biosynthesis; Psychiatry; Rats; Rats, Sprague-Dawley; Receptors, Nicotinic - metabolism; Receptors, Nicotinic - physiology; Substance Withdrawal Syndrome - metabolism; Substance Withdrawal Syndrome - prevention & control; Substance Withdrawal Syndrome - psychology
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-010-2101-7

Rationale Negative motivational withdrawal from acute opiate dependence was induced by an opioid antagonist, and the withdrawal signs prevented by pretreatment with nicotine. Objectives The present study was undertaken to examine the mechanism of nicotine-induced attenuation of withdrawal precipitated by naloxone in rats administered a single dose of morphine. Methods Conditioned place aversion (CPA) was precipitated by naloxone in rats exposed once to morphine. Nicotinic acetylcholine receptor (nAChR) agonists were microinjected into the central amygdaloid nucleus (CeA) before naloxone was administered. Additionally, c-Fos expression in the amygdala was measured in rats exposed to α7 nAChR ligands. Results The microinjection of nicotine (0.3 and 1.0 μg/μl) into the CeA dose-dependently inhibited naloxone-induced CPA. This inhibition of CPA was reversed by methyllycaconitine (MLA), an α7 nAChR antagonist. CPA was also significantly attenuated by the microinjection of tropisetron (3.0 μg/μl), an α7 nAChR agonist and 5-hydroxytriptamine 3 (5-HT 3 ) receptor antagonist, but not by ondansetron (1.0 and 3.0 μg/μl), a 5-HT 3 receptor antagonist. The microinjection of PNU-282987 (3.0 μg/μl), a selective α7 nAChR agonist, into the CeA also inhibited CPA. Furthermore, nicotine increased c-Fos expression in the CeA, but not the medial or basolateral amygdaloid nucleus. The increase of c-Fos in the CeA was significantly inhibited by MLA. Conclusion Nicotine-induced attenuation of CPA precipitated by naloxone is mediated by the α7 nAChR subtype, and the CeA is one of the regions of the brain involved in the effect of nicotine on acutely opiate-dependent subjects.