Salt appetite: interaction of forebrain angiotensinergic and hindbrain serotonergic mechanisms

Methysergide injected bilaterally into the lateral parabrachial nucleus (LPBN) increases NaCl intake in several models of renin-dependent salt appetite. The present study investigated the role of angiotensin Type 1 (AT1) receptors in the subfornical organ (SFO) on this effect. The intake of 0.3 M NaCl and water was induced by combined administration of the diuretic, furosemide (FURO), and the angiotensin-converting enzyme inhibitor, captopril (CAP). Pretreatment of the SFO with an AT1 receptor antagonist, losartan (1 microgram/200 nl), reduced water intake but not 0.3 M NaCl intake induced by subcutaneous FURO+CAP. Methysergide (4 microgram/200 nl) injected bilaterally into the LPBN increased 0.3 M NaCl intake after FURO+CAP. Losartan injected into the SFO prevented the additional 0. 3 M NaCl intake caused by LPBN methysergide injections. These results indicate that AT1 receptors located in the SFO may have a role in mediating an enhanced sodium intake produced by methysergide treatment.