Analysis of thermoregulatory responses in the process of heat-and cold-acclimatization

点击翻译按钮获取中文摘要

This study is performed to clarify the central and peripheral mechanism of thermal adaptation from the new concept of the extrahypothalamic deep body thermosenitivity. (1) The physiological changes that occur during heat acclimation were measured in six albino rabbits which had been reared at 30゜C (Ta) and 60% (RH) for 24 weeks continuously. During the experiment Ta was changed at a rate of 0.5゜C/min. The rectal temperature (Tre) change during Ta shift was 1.1 <+!-> 0.2 (Mean <+!-> SD) in the Heat acclimated rabbits compared to 1.6 <+!-> 0.3゜C in the control. The mean threshold level of Ta at which vasodilation of the ear began was 27.5 <+!-> 1.2゜C in the heat acclimated series compared to 25.0゜C in the controls. Conversely, vasoconstriction occured at 21.8 <+!-> 3.3゜C in the former compared to 14.7 <+!-> 2.9゜C in the later group. It is suggested that during heat acclimation there is a shift of the threshold temperature at which vasodilatation or vasoconstriction occurs. This is to pre … More vent changed of the core temperature. Further, under general anaesthesia (Nembutal 20mg/kg ip) there was no difference in the thresholds in the two series. It confirms that physiological changes in heat acclimation is through neuronal mechanisms influenced by anaesthesia sympathetic vasoconstrictor tones among the groups were measured after <IV> administration of adrenergic blocker (phentolamine mesylate 3mg/kg). At the same Te, there was greater vasodilation in the control than in the acclimated group, suggesting that vasoconstrictor tone is different between heat acclimated and non acclimated even at the same Ta. (2) In the present series of experiments, we tried to elucidate the nature of thermoregulation in responses to environ mental temperature shifts (25゜C 40゜C 10゜C 25゜C) in the rabbits devoid of pre-optic and anterior hypothalamic (PO/AH regions. Bilateral PO/AH lesions in male rabbits were accomplished using electrolytic procedure. And thermoregulator capabilities before and after PO/AH lesions were compared. In control rabbits, with the change in ambient temperature (Ta), the ear skin temperature (Tea) changed in the same direction. The change in rectal temperature (Tre) was small. In one-week-lesioned rabbit, the change of Tre was great when heated, but Tre was stable to cold stress. In two-weeks lesioned rabbit, Tre, inspite of Ta change, was quite stable: to the extent that it was comparable to the control rabbits. Therefore, these results should be interpreted as presenting the recovery of thermoregulatory functions after results should be interpreted as presenting the recovery of thermoregulatory functions after the PO/AH lesions. It is concluded that, without PO/AH participation, extrahypothalamic thermosenitive tissues were the places endowed with these thermorgulatory functions. Less