title: Activation of μ-opioid receptors in the central nucleus of the amygdala induces hypertonic sodium intake.
abstract: Opioid mechanisms are involved in the control of water and NaCl intake and opioid receptors (ORs) are present in the central nucleus of the amygdala (CeA), a site of important facilitatory mechanisms related to the control of sodium appetite. Therefore, in the present study we investigated the effects of the activation of μ-ORs in the CeA on 0.3 M NaCl and water intake in rats. Male Sprague-Dawley rats with stainless steel cannulas implanted bilaterally in the CeA were used. In rats submitted to water deprivation-partial rehydration, bilateral injections of the selective μ-OR agonist [D-Ala², N-Me-Phe⁴, Gly⁵-ol]-enkephalin (DAMGO) in the doses of 1, 2, and 4 nmol into the CeA induced a dose-related increase of 0.3M NaCl intake and water intake, and bilateral injections of the selective μ-OR antagonist D-Phe-Cys-Trp-Arg-Thr-Pen-Thr-NH₂ (CTAP) in the doses of 0.5, 1, and 2 nmol into the CeA produced a dose-related decrease of 0.3 M NaCl and water intake induced by DAMGO 2 nmol into the same site. In rats treated with the diuretic furosemide (10 mg/kg b.w.) combined with the angiotensin-converting enzyme inhibitor captopril (5 mg/kg b.w.) injected subcutaneously, bilateral injections of DAMGO 2 nmol into the CeA increased 0.3 M NaCl intake and water intake and the blockade of μ-ORs with CTAP 1 nmol injected into the CeA reduced the increase in 0.3 M NaCl intake and water intake induced by DAMGO 2 nmol into the same site. Bilateral injections of DAMGO into the CeA did not change urinary volume, sodium urinary excretion and mean arterial pressure, but increased activity. Thus stimulating μ-ORs in the CeA increases hypertonic sodium intake, whereas antagonizing these sites inhibits hypertonic sodium intake. Together, our results implicate μ-ORs in the CeA in a positive regulation of sodium intake.
authors.affiliation: Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi'an Jiaotong University College of Medicine, 76# W. Yanta Road, Xi'an, Shaanxi 710061, PR China.
authors.forename: Junbao
authors.initials: J
authors.lastname: Yan
authors.forename: Jinrong
authors.initials: J
authors.lastname: Li
authors.forename: Jianqun
authors.initials: J
authors.lastname: Yan
authors.forename: Huiling
authors.initials: H
authors.lastname: Sun
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Ke
authors.initials: K
authors.lastname: Chen
authors.forename: Bo
authors.initials: B
authors.lastname: Sun
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wei
authors.forename: Lin
authors.initials: L
authors.lastname: Song
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Zhao
authors.forename: Shuangyu
authors.initials: S
authors.lastname: Wei
authors.forename: Ling
authors.initials: L
authors.lastname: Han
mesh_terms: D000679:Amygdala / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001066:Appetite / Q000187:drug effects / Q000502:physiology*; D001069:Appetite Regulation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012462:Saline Solution, Hypertonic; D012982:Sodium, Dietary; D014868:Water Deprivation / Q000502:physiology
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D012462:Saline Solution, Hypertonic; D012982:Sodium, Dietary