Central 5-HT2B/2C and 5-HT3 receptor stimulation decreases salt intake in sodium-depleted rats

In the present study, we investigated the participation of central 5-HT2B/2C and 5-HT3 receptors in the salt intake induced by sodium depletion in Wistar male rats. Sodium depletion was produced by the administration of furosemide associated with a low salt diet. Third ventricle injections of mCPP, a 5-HT2B/2C, agonist, at doses of 80, 160 and 240 nmol, promoted a dose-dependent reduction in salt intake in sodium-depleted rats. The inhibitory effect produced by central administration of mCPP was abolished by the central pretreatment with SDZ SER 082, a 5-HT2B/2C antagonist. Similar results were obtained with third ventricle injections of m-CPBG (80, 160 and 240 nmol), a selective 5-HT3 agonist that also induced a dose-related decrease in salt intake in sodium-depleted rats. The central pretreatment with LY-278,584, a selective 5-HT3 receptor antagonist, was able to impair the salt intake inhibition elicited by third ventricle injections of m-CPBG. Central administration of each one of the antagonists alone or a combination of both antagonists together did not significantly change salt intake after sodium depletion. On the other hand, the central administration of both mCPP and m-CPBG, in the highest dose used to test their effect on salt intake (240 nmol), was unable to modify blood pressure in sodium-depleted rats. It is concluded that: (1) pharmacological activation of central 5-HT2B/2C and 5-HT3 receptors diminishes salt intake during sodium depletion, (2) an inhibitory endogenous drive exerted by central 5-HT2B/2C and 5-HT3 receptors does not seem to exist and (3) the reduction in salt intake generated by the pharmacological activation of these central receptors is not produced by an acute hypertensive response. (C) 2003 Elsevier B.V. All rights reserved.