Diuretic-induced dehydration/hypovolemia inhibits thermal panting in rabbits.

Respiratory and thermoregulatory responses to hyperthermia during isosmotic dehydration/hypovolemia were studied in 17 anaesthetized adult rabbits divided into two groups: normovolemic group (NV; n=10) and hypovolemic group (HV; n=7). Hypovolemia/isosmotic dehydration (a decrease in plasma volume by 16.1+/-1.2%) was induced by furosemide (5 mg kg(-1) i.v.). During hyperthermia (the rise in body temperature to 42 degrees C by a gradual body surface heating), the HV rabbits had lower (P<0.05) respiratory frequency and higher (P<0.05) tidal volume than the NV animals. The panting was absent in the HV rabbits at the BT of 42 degrees C, unlike the NV animals. The lower respiratory frequency and the absence of panting during exogenous hyperthermia in dehydrated animals are present not only during hyperosmotic dehydration induced by water deprivation [Doris, P.A., Baker, M.A., 1981. Hypothalamic control of thermoregulation during dehydration. Brain Res. 206 (1), 219-222], but they also occur in the furosemide-induced isosmotic dehydration/hypovolemia.