title: β-Endorphinergic system involvement in the inhibitory action of clonidine on induced sodium appetite.
abstract: In the present study, we investigated the degree to which β-endorphin plays a role in the alpha 2-adrenergic/imidazoline receptor agonist attenuation of salt appetite. In order to evaluate whether the inhibitory action of clonidine (an α2-adrenergic/imidazoline receptor agonist) on induced sodium intake is mediated by the β-endorphinergic system, we used a β-endorphin deficient mouse line. β-endorphin knockout (βend(-/-)), heterozygous (βend(+/-)) and wild-type (βend(+/+)) mice were submitted to acute sodium depletion by a combined treatment of furosemide and low sodium diet and, 20h later, were administered with clonidine (0.5mg/kg). An hour later, the animals were subjected to a two-bottle choice test (water/2% NaCl). The results indicate that clonidine administration during the first stage of the test exerts an equivalent inhibition on sodium intake regardless of the genotype; however, in the final stage of the test, a reversal of the inhibitory response on induced sodium appetite becomes evident in the mice lacking β-endorphin. Moreover no differences in dipsogenic response were observed between the genotypes. Considering these results and the fact that plasma half-life of clonidine at the dose administered is approximately 3h, it is possible to speculate that the inhibitory effect of clonidine on sodium appetite may be independent of β-endorphin modulation during the first stage; however, the long-lasting inhibitory effect of clonidine may be mediated by the β-endorphinergic system. This evidence supports the existence of adrenergic and β-endorphinergic system interaction in the osmoregulatory response to achieve sodium balance.
authors.affiliation: Instituto de Investigación Médica Mercedes y Martin Ferreyra (INIMEC-CONICET), Casilla de Correo 389-5000, Córdoba, Argentina.
authors.forename: X E
authors.initials: XE
authors.lastname: Caeiro
authors.forename: A
authors.initials: A
authors.lastname: Godino
authors.forename: L
authors.initials: L
authors.lastname: Vivas
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D001066:Appetite / Q000187:drug effects*; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D004326:Drinking / Q000502:physiology; D005665:Furosemide / Q000494:pharmacology; D054755:Imidazoline Receptors / Q000819:agonists*; D051379:Mice; D008815:Mice, Inbred Strains; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*; D001615:beta-Endorphin / Q000502:physiology*
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D054755:Imidazoline Receptors; D018341:Receptors, Adrenergic, alpha-2; D017673:Sodium Chloride, Dietary; D001615:beta-Endorphin; D005665:Furosemide; D003000:Clonidine