Central administration of mCPP, a serotonin 5-HT(2B/2C) agonist, decreases water intake in rats.

In the present study, we investigated in rats the effect of third ventricle injections of 1-(3-chlorophenyl)piperazine (mCPP), a 5-HT(2) receptor agonist, on water intake induced by three different physiological stimuli: fluid deprivation, acute salt load and hypovolemia. Injections of mCPP in the doses of 80 and 160 nmol/rat were able to decrease water intake in all three conditions studied. Third ventricle injections of mCPP (160 nmol/rat) were no longer able to diminish water intake in the groups of rats pretreated with central injections of an equimolar amount of (+)-cis-4,5,7a,8,9,10,11,11a-octahydro-7H-10-methylindolo[1,7-bc][2,6]-naphthyridine (SDZ SER 082), a selective 5-HT(2B/2C) antagonist. The central administration of mCPP (160 nmol/rat) was not able to modify the intake of a 0.1% saccharin solution. It is suggested that the central activation of a 5-HT(2B/2C) component is able to impair the drive for water intake induced by the physiological stimuli represented by fluid deprivation, acute salt load and hypovolemia. This effect seems not to be consequent on a general nonspecific central nervous system depression or on a locomotor deficit, because saccharin intake is not affected by third ventricle injections of mCPP.