Inhibition of sodium appetite by lipopolysaccharide: involvement of alpha2-adrenoceptors.

Abstract

Lipopolysaccharide (LPS), an endotoxin from the wall of Escherichia coli, produces a general behavioral inhibition and affects several aspects of fluid-electrolyte balance. LPS inhibits thirst; however, it is not clear if it also inhibits sodium appetite. The present results show that LPS (0.3-2.5 mg/kg body wt) injected intraperitoneally produces a dose-dependent reduction of sodium appetite expressed as 0.3 M NaCl intake induced by sodium depletion (furosemide plus removal of ambient sodium for 24 h). The high doses of LPS (1.2-2.5 mg/kg) also produced transient hypothermia at the beginning of the sodium appetite test; however, no dose produced hyperthermia. LPS also increased the stomach liquid content (an index of gastric emptying) after a load of 0.3 M NaCl given intragastrically by gavage to sodium-depleted rats. The α(2)-adrenoceptor antagonist yohimbine (5 mg/kg ip) abolished the effect of LPS on 0.3 M NaCl intake, without changing the effect of LPS on gastric emptying. Injection of RX-821002 (160 nmol), another α(2)-adrenoceptor antagonist, in the lateral cerebral ventricle (LV) also reversed the inhibition of sodium appetite produced by LPS. Yohimbine intraperitoneally or RX-821002 in the LV alone had no effect on sodium intake. Although yohimbine plus LPS produced a slight hypotension, RX-821002 plus LPS produced no change in arterial pressure, suggesting that the blockade of the effects of LPS on sodium intake by the α(2)-adrenoceptor antagonists is independent from changes in arterial pressure. The results suggest an inhibitory role for LPS in sodium appetite that is mediated by central α(2)-adrenoceptors.

• Authors: R L Almeida, R B David, J Constancio, J F Fracasso, J V Menani, L A De Luca Jr
• Journal: American journal of physiology. Regulatory, integrative and comparative physiology (Am J Physiol Regul Integr Comp Physiol) Vol. 301 Issue 1 Pg. R185-92 (Jul 2011) ISSN: 1522-1490 [Electronic] United States
• PMID: 21474430 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adrenergic alpha-2 Receptor Antagonists
• Lipopolysaccharides
• Receptors, Adrenergic, alpha-2
• Sodium Chloride, Dietary
• Yohimbine
• 2-methoxyidazoxan
• Idazoxan

Topics

• Adrenergic alpha-2 Receptor Antagonists (pharmacology)
• Animals
• Appetite (drug effects, physiology)
• Blood Pressure (drug effects, physiology)
• Body Temperature (drug effects, physiology)
• Dose-Response Relationship, Drug
• Gastric Emptying (drug effects, physiology)
• Heart Rate (drug effects, physiology)
• Idazoxan (analogs & derivatives, pharmacology)
• Injections, Intraperitoneal
• Lipopolysaccharides (administration & dosage, pharmacology)
• Male
• Models, Animal
• Rats
• Rats, Sprague-Dawley
• Receptors, Adrenergic, alpha-2 (drug effects, physiology)
• Sodium Chloride, Dietary (metabolism)
• Yohimbine (pharmacology)