Serotonergic mechanisms of the lateral parabrachial nucleus in renal and hormonal responses to isotonic blood volume expansion.
This study investigated the involvement of serotonergic mechanisms of the lateral parabrachial nucleus (LPBN) in the control of sodium (Na+) excretion, potassium (K+) excretion, and urinary volume in unanesthetized rats subjected to acute isotonic blood volume expansion (0.15 M NaCl, 2 ml/100 g of body wt over 1 min) or control rats. Plasma oxytocin (OT), vasopressin (VP), and atrial natriuretic peptide (ANP) levels were also determined in the same protocol. Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used. In rats treated with vehicle in the LPBN, blood volume expansion increased urinary volume, Na+ and K+ excretion, and also plasma ANP and OT. Bilateral injections of serotonergic receptor antagonist methysergide (1 or 4 microg/200 etal) into the LPBN reduced the effects of blood volume expansion on increased Na+ and K+ excretion and urinary volume, while LPBN injections of serotonergic 5-HT(2a)/HT(2c) receptor agonist, 2.5-dimetoxi-4-iodoamphetamine hydrobromide (DOI; 1 or 5 microg/200 etal) enhanced the effects of blood volume expansion on Na+ and K+ excretion and urinary volume. Methysergide (4 microg) into the LPBN decreased the effects of blood volume expansion on plasma ANP and OT, while DOI (5 microg) increased them. The present results suggest the involvement of LPBN serotonergic mechanisms in the regulation of urinary sodium, potassium and water excretion, and hormonal responses to acute isotonic blood volume expansion.
Margatho
Lisandra Oliveira
LO
Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Avenida Bandeirantes 3900, 14049-900 Ribeirao Preto-Sao Paulo, Brazil.
Giusti-Paiva
Alexandre
A
Menani
Jose Vanderlei
JV
Elias
Lucila Leico Kagohara
LL
Vivas
Laura M
LM
Antunes-Rodrigues
Jose
J
D000662:Amphetamines / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood; D001810:Blood Volume; D004305:Dose-Response Relationship, Drug; D004327:Drinking Behavior / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D008784:Methysergide / Q000008:administration & dosage / Q000494:pharmacology*; D008845:Microinjections; D010121:Oxytocin / Q000097:blood; D011149:Pons / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000652:urine; D051381:Rats; D017208:Rats, Wistar; D044348:Receptors, Serotonin, 5-HT2 / Q000502:physiology*; D012702:Serotonin Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D012964:Sodium / Q000652:urine; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*; D013997:Time Factors; D014667:Vasopressins / Q000097:blood
D000662:Amphetamines; D044348:Receptors, Serotonin, 5-HT2; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D017673:Sodium Chloride, Dietary; D014667:Vasopressins; D010121:Oxytocin; D009320:Atrial Natriuretic Factor; D012964:Sodium; D011188:Potassium; D008784:Methysergide