Changes of hypothalamic and plasma vasopressin in rats with deoxycorticosterone-acetate induced salt appetite

Mineralocorticoids play a predominant role in development of salt appetite and hypertension. Since vasoactive peptides could mediate the central effec ts of mineralocorticoids, we evaluated changes of immunoreactive (IR) argin ine-vasopressin (AVP) in the paraventricular (PVN) and supraoptic (SON) hyp othalamic nucleus during DOCA-induced salt appetite. In one model, rats hav ing free access to water and 3% NaCl during 9 (prehypertensive stage) or 21 days (hypertensive stage) received DOCA (s.c., 10 mg/rat/in alternate days ). A decrease in the IR cell area, number of IR cells and staining intensit y was obtained in magnocellular PVN of rats treated during 9 days. After 21 days IR cell area and number of cells in the PVN also decreased, but stain ing intensity of remaining cells was normal. The same parameters were uncha nged in the SON. In another model, animals treated with DOCA during 9 days had only access to 3% NaCl or water. The IR cell area in PVN and SON signif icantly increased in mineralocorticoid-treated and control animals, both dr inking 3% NaCl. Staining intensity (PVN and SON) and number of IR cells (PV N) also augmented in DOCA-treated animals drinking salt respect of a group drinking water. Plasma AVP in rats treated with DOCA and offered salt and w ater, exhibited a 2-2.5 fold increase at the time of salt appetite inductio n. Plasma AVP was substantially higher in rats drinking salt only, while th e highest levels were present in salt-drinking DOCA-treated rats. Thus, pep tide depletion in the PVN may be due to increased release, because reduced levels of hypothalamic and posterior pituitary AVP were measured in this mo del. In rats drinking salt only the substantial increase of IR AVP in the P VN and SON, may be due to dehydration and hyperosmosis. Because DOCA-salt t reated rats showed higher AVP levels in the PVN compared to untreated rats drinking salt only, it is possible that DOCA sensitized PVN cells to increa se AVP production. The results suggest the vasopressinergic system could me diate some central functions of mineralocorticoids. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.