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Physiological stimuli of thirst and drinking patterns in ponies
Author(s) -
SUFIT ELIZABETH,
HOUPT KATHERINE A.,
SWEETING MARTHA
Publication year - 1985
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1985.tb02028.x
Subject(s) - thirst , liter , sodium , plasma osmolality , chemistry , endocrinology , medicine , zoology , horse , biology , paleontology , organic chemistry
Summary The stimuli that elicit thirst were studied in four ponies. Nineteen hours of water deprivation produced an increase in plasma protein from 67 ± 0.1 g/litre to 72 ± 2 g/litre, a mean (± se) increase in plasma sodium from 139 ± 3 to 145 ± 2 mmol/litre and an increase in plasma osmolality from 297 ± 1 to 306 ± 2 mosmol/litre. Undeprived ponies drank 1.5 ± 0.9 kg/30 mins; 19 h deprived ponies drank 10.2 ± 2.5 kg/30 mins and corrected the deficits in plasma protein, plasma sodium and plasma osmolality as well as compensating for the water they would have drunk during the deprivation period. In order to determine if an increase in plasma osmolality would stimulate thirst, 250 ml of 15 per cent sodium chloride was infused intravenously. The ponies drank when osmolality increased 3 per cent and when plasma sodium rose from 136 ± 3 mmol/litre to 143 ± 3 mmol/litre. Ponies infused with 15 per cent sodium chloride drank 2.9 ± 0.7 kg; those infused with 0.9 per cent sodium chloride drank 0.7 ± 0.5 kg. In order to determine if a decrease in plasma volume would stimulate thirst, ponies were injected with 1 or 2 mg/kg bodyweight (bwt) frusemide. Plasma protein rose from 68 ± 2 g/litre pre‐injection to 75 ± 2 g/litre 1 h after 1 mg/kg bwt frusemide and to 81 ± 1 g/litre 1 h after 2 mg/kg bwt frusemide. Ponies treated with 1 mg/kg frusemide voided 5.3 ± 0.81 kg urine and drank 3.0 ± 2 kg water. Ponies injected with 2 mg frusemide voided 6.4 ± 5 kg urine and drank 4.3 ± 1.4 kg water. Controls injected with 0.9 per cent sodium chloride voided 1.5 ± 0.5 kg urine and drank 0.9 ± 0.6 kg water. When food and water were freely available the ponies drank 27 ± 8 mins/day, 89 per cent of which occurred within a period from 10 mins before to 30 mins after feeding. They drank 8.7 ± 0.9 kg/day at a rate of 552 ± 232 ml/min. It was concluded that ponies usually drink periprandially and when challenged with either an increase in the osmotic pressure of their body fluids or a decrease in the volume of their body fluids they responded by increasing their water intake.