Effects of central imidazolinergic and alpha2-adrenergic activation on water intake.
Non-adrenergic ligands that bind to imidazoline receptors (I-R), a selective ligand that binds to alpha2-adrenoceptors (alpha2-AR) and mixed ligands that bind to both receptors were tested for their action on water intake behavior of 24-h water-deprived rats. All drugs were injected into the third cerebral ventricle. Except for agmatine (80 nmol), mixed ligands binding to I-R/alpha2-AR such as guanabenz (40 nmol) and UK 14304 (20 nmol) inhibited water intake by 65% and up to 95%, respectively. The selective non-imidazoline alpha2-AR agonist, alpha-methylnoradrenaline, produced inhibition of water intake similar to that obtained with guanabenz, but at higher doses (80 nmol). The non-adrenergic I-R ligands histamine (160 nmol, mixed histaminergic and imidazoline ligand) and imidazole-4-acetic acid (80 nmol, imidazoline ligand) did not alter water intake. The results show that selective, non-imidazoline alpha2-AR activation suppresses water intake, and suggest that the action on imidazoline sites by non-adrenergic ligands is not sufficient to inhibit water intake.
Sugawara
A M
AM
Departamento de Fisiologia e Patologia, Faculdade de Odontologia, Universidade Estadual Paulista, Araraquara, SP, Brasil.
Miguel
T T
TT
Pereira
D T
DT
Menani
J V
JV
De Luca
L A
LA
D058647:Adrenergic alpha-2 Receptor Agonists; D000818:Animals; D000068438:Brimonidine Tartrate; D004326:Drinking / Q000187:drug effects*; D006146:Guanidines / Q000494:pharmacology*; D007093:Imidazoles / Q000819:agonists / Q000494:pharmacology*; D007276:Injections, Intraventricular; D008024:Ligands; D008297:Male; D008771:Nordefrin / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014868:Water Deprivation
D058647:Adrenergic alpha-2 Receptor Agonists; D006146:Guanidines; D007093:Imidazoles; D008024:Ligands; D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D014662:Vasoconstrictor Agents; D000068438:Brimonidine Tartrate; D008771:Nordefrin