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Effects of intravenous tryptophan infusion on thermoregulation in steers exposed to acute heat stress
Author(s) -
Sutoh Madoka,
Kasuya Etsuko,
Yayou Kenichi
Publication year - 2018
Publication title -
animal science journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.606
H-Index - 38
eISSN - 1740-0929
pISSN - 1344-3941
DOI - 10.1111/asj.12988
Subject(s) - thermoregulation , hyperthermia , endocrinology , homeothermy , chemistry , serotonin , medicine , tryptophan , cerebrospinal fluid , rectal temperature , saline , prolactin , zoology , anesthesia , biology , hormone , biochemistry , receptor , amino acid
This study was conducted to investigate the effect of tryptophan ( TRP ) supply on the thermoregulatory responses via brain serotonin (5‐ HT ) in cattle. In period 1, 12 Holstein steers were kept under a constant room temperature (22°C) and were administered the intravenous (i.v.) infusion of saline or TRP (38.5 mg/kg/2 h). Changes in rectal temperature ( RT ), 5‐ HT concentration in the cerebrospinal fluid ( CSF ), and other factors involved in thermoregulation were measured. In period 2, the steers received the same treatments as in period 1; however, the room temperature was elevated from 22°C to 33°C during i.v. infusion and maintained at 33°C for 3 h. 5‐ HT concentration in CSF increased following TRP infusion in both periods, and RT significantly decreased following TRP infusion only in period 2. The effect of TRP on respiration rate and plasma prolactin and total triiodothyronine concentrations was not significant. These results suggest that increase in TRP supply can attenuate increase in RT in response to acute heat stress through the increase in brain 5‐ HT , followed by presumable increase in evaporative heat loss from the skin surface in cattle. It is possible that the increase in peripheral blood TRP metabolites could also participate in the hypothermic effect of TRP .