title: Blockade of central delta-opioid receptors inhibits salt appetite in sodium-depleted rats.
abstract: Various studies have investigated the role of central opioid peptides in feeding behavior; however, only a few have addressed the participation of opioids in the control of salt appetite. The present study investigated the effect of intracerebroventricular injections of the δ-opioid antagonist, naltrindole (5, 10 and 20 nmol/rat) and the agonist, deltorphin II (2.5, 5, 10 and 20 nmol/rat) on salt intake. Two protocols for inducing salt intake were used: sodium-depletion and the central injection of angiotensin II. In addition, the effect of a central δ-opioid receptor blockade on locomotor activity, on palatable solution intake (0.1% saccharin) and on blood pressure was also studied. The blockade of central δ-opioid receptors inhibits salt intake in sodium-depleted rats, while the pharmacological stimulation of these receptors increases salt intake in sodium-replete animals. Furthermore, the blockade of central δ-opioid receptors inhibits salt intake induced by central angiotensinergic stimulation. These data suggest that during sodium-depletion activation of the δ-opioid receptors regulates salt appetite to correct the sodium imbalance and it is possible that an interaction between opioidergic and angiotensinergic brain system participates in this control. Under normonatremic conditions, δ-opioid receptors may be necessary to modulate sodium intake, a response that could be mediated by angiotensin II. The decrease in salt intake following central δ-opioid receptors blockade does not appear to be due to a general inhibition of locomotor activity, changes in palatability or in blood pressure.
authors.affiliation: Department of Biological Sciences, State University of Southwest Bahia, 45200-000 Jequié, Bahia, Brazil; Department of Physiology, Health Sciences Institute, Federal University of Bahia, 40110-100 Salvador, Bahia, Brazil.
authors.forename: A I R
authors.initials: AI
authors.lastname: Nascimento
authors.affiliation: Life Sciences Department, Bahia State University, 41195-001 Salvador, Bahia, Brazil.
authors.forename: H S
authors.initials: HS
authors.lastname: Ferreira
authors.affiliation: Department of Physiology, Health Sciences Institute, Federal University of Bahia, 40110-100 Salvador, Bahia, Brazil.
authors.forename: D R
authors.initials: DR
authors.lastname: Cerqueira
authors.affiliation: Department of Physiology, Health Sciences Institute, Federal University of Bahia, 40110-100 Salvador, Bahia, Brazil. Electronic address: josmara@ufba.br.
authors.forename: J B
authors.initials: JB
authors.lastname: Fregoneze
mesh_terms: D000818:Animals; D001066:Appetite / Q000187:drug effects*; D001794:Blood Pressure; D004327:Drinking Behavior / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D009292:Narcotic Antagonists / Q000008:administration & dosage*; D009842:Oligopeptides / Q000494:pharmacology; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012964:Sodium / Q000172:deficiency*; D017673:Sodium Chloride, Dietary / Q000378:metabolism
chemical_list: D009292:Narcotic Antagonists; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D017673:Sodium Chloride, Dietary; C060209:deltorphin II, Ala(2)-; D009271:Naltrexone; D012964:Sodium; C055382:naltrindole
keywords: Angiotensin II; Delta-opioid receptors; Salt intake; Sodium-depletion