Physiology and Behavior

Texto completo: acesso restrito. p. 349-359 Submitted by Suelen Reis (suelen_suzane@hotmail.com) on 2012-12-12T14:48:09Z No. of bitstreams: 1 1-s2.0-S0031938402008727-main.pdf: 268735 bytes, checksum: 6a4ba32525f9591de29195d24b6ec41e (MD5) Made available in DSpace on 2012-12-12T14:48:09Z (GMT). No. of bitstreams: 1 1-s2.0-S0031938402008727-main.pdf: 268735 bytes, checksum: 6a4ba32525f9591de29195d24b6ec41e (MD5) Previous issue date: 2002-11 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-HT3 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-HT3 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-HT3 receptor activation exerts a specific inhibitory effect on water intake.