Central 5-HT(3) receptors and water intake in rats.
In the present paper, we studied in rats the effect of third ventricle administration of m-chlorophenylbiguanide hydrochloride (1-(3-chlorophenyl)biguanide (m-CPBG), a selective 5-HT(3) agonist, on water intake induced by three different physiological stimuli: water deprivation, acute salt load and hypovolemia. Central acute m-CPBG injections in the doses of 80 and 160 nmol significantly reduced water intake elicited by an acute salt load. Third ventricle injections of m-CPBG in the dose of 160 nmol significantly inhibited water intake in hypovolemic animals, whereas third ventricle injections of m-CPBG in a higher dose (320 nmol) were necessary to decrease water intake in water-deprived rats. Pretreatment with 1-methyl-N-[8-methyl-8-azabicyclo(3.2.1)-oct-3-yl]-1H-indazole-3-carboxamide (LY-278,584), a selective 5-HT(3) antagonist, abolished the inhibitory effect on water intake seen after central administration of m-CPBG in all groups studied. The central administration of m-CPBG was also able to inhibit water intake induced by pharmacological activation of central cholinergic and angiotensinergic pathways. Third ventricle injections of m-CPBG in the highest dose employed in this study (320 nmol) were unable to modify food intake in food-deprived rats. An aversion test has shown that acute third ventricle injections of m-CPBG do not induce illness-like effects that could explain the water intake inhibition here observed. Also, central administration of m-CPBG did not modify the intake of a "dessert" meal consisting of diluted condensed milk. It is concluded that central 5-HT(3) receptor activation exerts a specific inhibitory effect on water intake.
Castro
Letícia
L
Department of Physiology, Health Sciences Institute, Federal University of Bahia, 40110-100 Salvador, Bahia, Brazil.
Varjão
Bruno
B
Maldonado
Igor
I
Campos
Igor
I
Duque
Bruno
B
Fregoneze
Josmara
J
Reis de Oliveira
Irismar
I
De Castro-e-Silva
Emílio
E
D000809:Angiotensins / Q000502:physiology; D000818:Animals; D017776:Autonomic Pathways / Q000187:drug effects / Q000502:physiology; D001362:Avoidance Learning / Q000187:drug effects; D001645:Biguanides / Q000494:pharmacology; D001923:Brain Chemistry / Q000187:drug effects*; D004326:Drinking / Q000187:drug effects*; D004435:Eating / Q000187:drug effects; D007191:Indazoles / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009994:Osmolar Concentration; D010275:Parasympathetic Nervous System / Q000502:physiology; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects*; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D014868:Water Deprivation / Q000502:physiology
D000809:Angiotensins; D001645:Biguanides; D007191:Indazoles; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D014326:Tropanes; C061531:LY 278584; D011092:Polyethylene Glycols; C065734:1-(3-chlorophenyl)biguanide