Hypothalamic thermal stimulation modulates vasopressin release in hyperosmotically stimulated rabbits
Keil, R.; Gerstberger, R.; Simon, E.
American Journal of Physiology 267(4 Pt 2): R1089-R1097
1994
ISSN/ISBN: 0002-9513 PMID: 7943420 Document Number: 423118
Under thermoneutral conditions conscious rabbits received systemic infusions of NaCl as hypertonic solution (90 mu-eq cntdot min-1 cntdot kg body wt-1), which raised their plasma osmolality from 283 to 312 mosmol/kgH-2O. Rabbits receiving isotonic saline served as controls. Hypertonic stimulation induced a 60% reduction of both respiratory frequency and evaporative water loss. Rectal temperature rose by 0.4 degree C despite enhanced peripheral vasodilation as indicated by increased ear skin temperature. Plasma vasopressin (AVP), aldosterone (ALDO), and corticosterone (COR) were significantly elevated from 6 to 16 pg/ml, 90 to 180 pg/ml, and 17 to 40 ng/ml, respectively. To elucidate the importance of central temperature for AVP and adrenal corticosteroid release, hypothalamic thermal stimulations (20 min) were superimposed during established iso- and hyperosmotic steady-state conditions. Different from isosmotic controls, hyperosmotic animals responded to hypothalamic cooling (37 degree C) with a significant decrease in plasma AVP from 16 to 13 pg/ml and to hypothalamic warming (41 degree C) with a significant rise from 16 to 19 pg/ml. A weak temperature effect on COR release was also disclosed, especially of hypothalamic cooling, which significantly lowered plasma COR from 42 to 34 ng/ml. These results provide evidence for positive local temperature coefficients of hypothalmic control of AVP release and suggest a similar property also for the control of COR release by the hypothalamo-adenohypophysial axis.