Oxytocin polyuria and polydipsia is blocked by NaCl administration in food-deprived male rats.
We examined the effects of NaCl injections on the polydipsia and polyuria induced by subcutaneous oxytocin (OT) administration in food-deprived male rats. During the first 12 h of the treatment day, both food deprivation and OT administration increased urine excretion but reduced water intake, water balance (fluid intake minus urine volume) and body weight. OT treatment enhanced urine excretion and the reduction in water balance and body weight without reducing the water intake of food-deprived animals. Analysis of the physiological effects of OT administration showed increases in urinary sodium concentration, sodium excretion and a reduced plasma sodium concentration. During the second 12 h, OT increased both urine excretion and water intake in food-deprived but not in ad lib.-fed rats. However, hypertonic NaCl administration at the start of this second 12-h period blocked the polyuric and polydipsic responses observed in the OT/deprived group but increased the water intake of the ad lib. groups. After the whole 24-h period, animals treated with OT showed a water balance and body weight change matching those observed in Control animals. Although the recording time period is a critical factor to demonstrate the effect of peripheral OT administration on water intake, the results obtained suggest that the polyuric and polydipsic responses observed in food-deprived animals depend on the negative sodium and water balance induced by the natriuretic effect of OT and the unavailability of sodium. These OT-induced deficits can be counteracted by the administration of hypertonic NaCl solutions or simply by the intake of standard food.
Bernal
A
A
Psychobiology, University of Granada, Granada, Spain. Department of Physiology, School of Medicine, University of Granada, Granada, Spain. antoniobernal@ugr.es
Mahía
J
J
García Del Rio
C
C
Puerto
A
A
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004326:Drinking / Q000187:drug effects*; D004327:Drinking Behavior / Q000187:drug effects*; D004435:Eating; D005508:Food Deprivation / Q000502:physiology*; D008297:Male; D010121:Oxytocin / Q000494:pharmacology*; D011141:Polyuria / Q000139:chemically induced*; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000494:pharmacology*
D012965:Sodium Chloride; D010121:Oxytocin