Tøien Ø, Mercer J B
Department of Arctic Biology and Institute of Medical Biology, University of Tromso, N-9037 Tromso, Norway.
Pflugers Arch. 1996 May;432(1):66-74. doi: 10.1007/s004240050106.
Thermosensitivity (TS) and threshold core temperature for metabolic cold defence were determined in six conscious rabbits before, and at seven different times after i.v. injection of killed Staphylococcus aureus (8 x 10(7) or 2 x 10(7) cell walls x kg(-1)) by exposure to short periods (5-10 min) of body cooling. Heat was extracted with a chronically implanted intravascular heat exchanger. TS was calculated by regression of metabolic heat production (M) and core temperature, as indicated by hypothalamic temperature. Threshold for cold defence (shivering threshold) was calculated as the core temperature at which the thermosensitivity line crossed preinjection resting M. The shivering thresholds followed the shape of the fever response. TS was significantly reduced (up to 49%) during the time course of fever induced by the highest dose of pyrogen only. At both high and low doses of pyrogen TS correlated negatively with shivering threshold (r = 0.66 and 0.79 respectively) with similar slopes. The reduction in TS during fever was thus associated with the increase in shivering threshold resulting from the pyrogen injection and not by the dose of pyrogen. Model considerations indicate, however, that changes in sensitivity of the thermosensory input to the hypothalamic controller may affect threshold changes but cause negligible TS changes. It is more likely that the reduction in TS is effected in the specific hypothalamic effector pathways.
通过使清醒的6只兔子短时间（5 - 10分钟）身体冷却，测定静脉注射灭活金黄色葡萄球菌（8×10⁷或2×10⁷细胞壁×kg⁻¹）之前及之后7个不同时间点的热敏感性（TS）和代谢性冷防御的阈值核心温度。热量通过长期植入的血管内热交换器提取。TS通过代谢产热（M）与核心温度的回归计算得出，核心温度以下丘脑温度表示。冷防御阈值（寒战阈值）计算为热敏感性线与注射前静息M相交时的核心温度。寒战阈值遵循发热反应的形状。仅在最高剂量热原诱导的发热过程中，TS显著降低（高达49%）。在高剂量和低剂量热原时，TS均与寒战阈值呈负相关（r分别为0.66和0.79），斜率相似。因此，发热期间TS的降低与热原注射导致的寒战阈值升高有关，而非热原剂量。然而，模型分析表明，热感觉输入对下丘脑控制器的敏感性变化可能影响阈值变化，但导致的TS变化可忽略不计。TS降低更可能发生在下丘脑特定效应器途径中。
