Central moxonidine on water and NaCl intake.
In this study we investigated: (a) the effects of intracerebroventricular (i.c.v.) injections of moxonidine (an alpha2-adrenergic and imidazoline receptor agonist) on the ingestion of water and NaCl induced by 24 h of water deprivation; (b) the effects of i.c.v. injection of moxonidine on central angiotensin II (ANG II)- and carbachol-induced water intake; (c) the effects of the pre-treatment with i.c.v. idazoxan (an alpha2-adrenergic and imidazoline receptor antagonist) and RX 821002 (a selective alpha2-adrenergic antagonist) on the antidipsogenic action of central moxonidine. Male Holtzman rats had stainless steel cannulas implanted in the lateral cerebral ventricle. Intracerebroventricular injection of moxonidine (5 and 20 nmol/1 microl) reduced the ingestion of 1.5% NaCl solution (4.1 +/- 1.1 and 2.9 +/- 2.5 ml/2 h, respectively vs. control = 7.4 +/- 2.1 ml/2 h) and water intake (2.0 +/- 0.6 and 0.3 +/- 0.2 ml/h, respectively vs. control = 13.0 +/- 1.4 ml/h) induced by water deprivation. Intracerebroventricular moxonidine (5 nmol/1 microl) also reduced i.c.v. ANG II-induced water intake (2.8 +/- 0.9 vs. control = 7.9 +/- 1.7 ml/1 h) and i.c.v. moxonidine (10 and 20 nmol/1 microl) reduced i.c.v. carbachol-induced water intake (4.3 +/- 1.7 and 2.1 +/- 0.9, respectively vs. control = 9.2 +/- 1.0 ml/1 h). The pre-treatment with i.c.v. idazoxan (40 to 320 nmol/1 microl) abolished the inhibitory effect of i.c.v. moxonidine on carbachol-induced water intake. Intracerebroventricular idazoxan (320 nmol/1 microl) partially reduced the inhibitory effect of moxonidine on water deprivation-induced water intake and produced only a tendency to reduce the antidipsogenic effect of moxonidine on ANG II-induced water intake. RX 821002 (80 and 160 nmol/1 microl) completely abolished the antidipsogenic action of moxonidine on ANG II-induced water intake. The results show that central injections of moxonidine strongly inhibit water and NaCl ingestion. They also suggest the involvement of central alpha2-adrenergic receptors in the antidipsogenic action of moxonidine.
Menani
J V
JV
Departamento de Ciências Fisiológicas, Faculdade de Odontologia de Araraquara, UNESP, Brazil. menani@foar.unesp.br
Sato
M A
MA
Haikel
L
L
Vieira
A A
AA
de Andrade
C A
CA
da Silva
D C
DC
Renzi
A
A
De Luca
L A
LA
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000494:pharmacology; D002217:Carbachol / Q000008:administration & dosage / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000008:administration & dosage / Q000494:pharmacology; D004326:Drinking / Q000187:drug effects*; D019329:Idazoxan / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000008:administration & dosage* / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000959:Antihypertensive Agents; D018679:Cholinergic Agonists; D007093:Imidazoles; D017673:Sodium Chloride, Dietary; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D002217:Carbachol; C043482:moxonidine; C058525:2-methoxyidazoxan; D019329:Idazoxan