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Ionic control of thermoregulation in the laying hen
Abstract
In the last decade the significance of cation involvement in body temperature regulation has become of increasing interest in many species. The endogenous and pharmacological action of cations in laying hens exposed to thermal challenge was investigated and metabolic activity of brain regions was identified and quantified. In the thermoneutral zone, ICV injection of Na$\sp+$ or Ca$\sp{+2}$ produced an increase or a decrease in body temperature similar to broilers and mammals. However, under thermal challenge the action of Ca$\sp{+2}$ or Na$\sp+$ appeared to be prevented or attenuated, possibly suggesting that heat altered endogenous cerebrospinal cation concentration. This speculation was tested; it was found that the alteration in cation concentration did indeed occur under thermal challenge. However, Ca$\sp{+2}$ ions seem to be involved with both hot and cool temperatures. The source of this Ca$\sp{+2}$ or its mechanism of action is not known at present. Ouabain and EGTA were injected ICV to elucidate the role of Na$\sp+$ and/or Ca$\sp{+2}$. The response to EGTA was similar to the pharmacological action of Na$\sp+$. It was intensified with heat. Addition of EGTA may stimulate the Na$\sp+$ pump by sequestration of Ca$\sp{+2}$, causing a relative increase in Na$\sp+$ ions. Ouabain, however, did not produce the expected drop in body temperature. The presence of multiple Na$\sp+$ transport systems may account for this. The change in functional activity (as detected by change of $\sp{14}$C-deoxyglucose uptake) of various brain regions during central (ICV injection of Ca$\sp{+2}$) or peripheral thermal stimulation showed involvement of midbrain, mainly hypothalamic and thalamic nuclei, and forebrain regions. Ca$\sp{+2}$ ions seemed to act on the same nuclei as were stimulated peripherally. Their action, however, was more general. The data strongly implicate the involvement of Ca$\sp{+2}$ and Na$\sp+$ in body temperature regulation. Calcium appears to be more active, possibly through Na$\sp+$-ATPase. Further research is suggested to elucidate the mechanism of action and the source of the ions.
Subject Area
Livestock
Recommended Citation
Maki, Auday Ahmed, "Ionic control of thermoregulation in the laying hen" (1988). ETD collection for University of Nebraska-Lincoln. AAI8818639.
https://digitalcommons.unl.edu/dissertations/AAI8818639