Whole body sodium depletion modifies AT1 mRNA expression and serotonin content in the dorsal raphe nucleus.

Angiotensin II (Ang II) acts on Ang II type 1 (AT1) receptors located in the organum vasculosum and subfornical organ (SFO) of the lamina terminalis as a main facilitatory mechanism of sodium appetite. The brain serotonin (5-HT) system with soma located in the dorsal raphe nucleus (DRN) provides a main inhibitory mechanism. In the present study, we first investigated the existence of Ang II AT1 receptors in serotonergic DRN neurones.

Blockade of 5-Ht3 receptors in the septal area increases Fos expression in selected brain areas.

Serotonin is widely distributed throughout the brain and is involved in a multiplicity of visceral, cognitive and behavioral responses. It has been previously shown that injections of different doses of ondansetron, a 5-HT3 receptor antagonist, into the medial septum/vertical limb of the diagonal band complex (MS/vDB) induce a hypertensive response in rats. On the other hand, administration of m-CPBG, a 5-HT3 agonist, into the MS/vDB inhibits the increase of blood pressure during restraint stress.

Hypothalamic disconnection caudal to paraventricular nucleus affects cardiovascular and drinking responses to central angiotensin II and carbachol.

The paraventricular nucleus of the hypothalamus (PVN) is an important area of the brain involved in the control of cardiovascular system and fluid-electrolyte balance. In the present study we evaluated the effects of hypothalamic disconnection (HD) caudal to PVN in the pressor and dipsogenic responses induced by intracerebroventricular (icv) injections of angiotensin II (ANG II) or carbachol (cholinergic agonist). Male Holtzman rats (280-320 g) with a stainless steel cannula implanted into the lateral ventricle and submitted to sham or HD surgery were used.

Blockade of 5-HT3 receptors at septal area increase blood pressure in unanaesthetized rats.

In the present study the role of 5-HT(3) receptors located at the medial septum/vertical limb of the diagonal band complex (MS/vDB) in the control of blood pressure in unanaesthetized rats was investigated. Microinjections of ondansetron, a selective 5-HT(3) receptor antagonist, into this area caused a dose-dependent increase in blood pressure. This rise was attenuated by the blockade of alpha-adrenoceptors with i.