RESUMO
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.
Assuntos
Ingestão de Líquidos/efeitos dos fármacos , Piperazinas/farmacologia , Receptores de Serotonina/efeitos dos fármacos , Agonistas do Receptor de Serotonina/farmacologia , Animais , Depressão Química , Hipovolemia/metabolismo , Injeções Intraventriculares , Masculino , Concentração Osmolar , Piperazinas/administração & dosagem , Ratos , Ratos Wistar , Receptor 5-HT2B de Serotonina , Receptor 5-HT2C de Serotonina , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/administração & dosagem , Privação de Água/fisiologiaRESUMO
We demonstrate here that acute third ventricle injections of GR 113808, a highly selective 5-HT4 antagonist, decrease water intake induced by a previous salt load while potentiating drinking elicited by hypovolemia induced by previous subcutaneous administration of polyethylene glycol in male Wistar rats (200 + or - 20 g). At the dose of 160 nmol/rat, third ventricle injections of GR 113808 induced a significant reduction of water intake in salt-loaded animals after 120 min as compared to salt-loaded animals receiving third ventricle injections of saline (salt load + GR = 3.44 + or - 0.41 ml, N = 12; salt load + saline = 5.74 + or - 0.40 ml, N = 9). At the dose of 80 nmol/rat, GR 113808 significantly enhanced water intake in hypovolemic animals after 120 min as compared to hypovolemic animals receiving third ventricle injections of saline (hypovol + GR = 4.01 + or - 0.27 ml, N = 8; hypovol + saline = 2.41 + or - 0.23 ml, N = 12). We suggest that central 5-HT4 receptors may exert a positive drive on water intake due to hyperosmolarity and a negative input on drinking provoked by hypovolemia.
Assuntos
Animais , Masculino , Ratos , Ingestão de Líquidos/efeitos dos fármacos , Hipovolemia/metabolismo , Indóis/farmacologia , Antagonistas da Serotonina/farmacologia , Terceiro Ventrículo , Injeções Intraventriculares , Concentração Osmolar , Ratos WistarRESUMO
We demonstrate here that acute third ventricle injections of GR 113808, a highly selective 5-HT4 antagonist, decrease water intake induced by a previous salt load while potentiating drinking elicited by hypovolemia induced by previous subcutaneous administration of polyethylene glycol in male Wistar rats (200 +/- 20 g). At the dose of 160 nmol/rat, third ventricle injections of GR 113808 induced a significant reduction of water intake in salt-loaded animals after 120 min as compared to salt-loaded animals receiving third ventricle injections of saline (salt load + GR = 3.44 +/- 0.41 ml, N = 12; salt load + saline = 5.74 +/- 0.40 ml, N = 9). At the dose of 80 nmol/rat, GR 113808 significantly enhanced water intake in hypovolemic animals after 120 min as compared to hypovolemic animals receiving third ventricle injections of saline (hypovol + GR = 4.01 +/- 0.27 ml, N = 8; hypovol + saline = 2.41 +/- 0.23 ml, N = 12). We suggest that central 5-HT4 receptors may exert a positive drive on water intake due to hyperosmolarity and a negative input on drinking provoked by hypovolemia.