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 °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 °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.