ANTAGONISM OF CLONIDINE INJECTED INTRACEREBROVENTRICULARLY IN DIFFERENT MODELS OF SALT INTAKE

Clonidine, an alpha 2-adrenergic agonist, injected into the brain inhi bits salt intake of animals treated by the diuretic model of sodium de pletion. In the present study, we address the question of whether cent ral injection of clonidine also inhibits salt intake in animals depriv ed of water or in the need-free state. Saline or clonidine (30 nmol) w as injected into the anterior third ventricle of 24-h sodium-depleted (furosemide + removal of ambient sodium), of 24-h water-deprived and o f normovolemic (need-free state) adult male rats, Clonidine injected i ntracerebroventricularly (icv) inhibited the 1.5% NaCl intake for 120 min by 50 to 90% in every model tested. Therefore, different models of salt intake are inhibited by icv injection of clonidine, Idazoxan, an alpha 2-adrenergic antagonist, injected icy at a dose of 160 nmol, in hibited the effect of clonidine only in the furosemide + removal of am bient sodium model of salt intake. This indicates that the antagonism of this effect by idazoxan is dependent on the body fluid/sodium statu s of the animal.