Roberts W W
Department of Psychology, University of Minnesota, Minneapolis 55455.
Ann N Y Acad Sci. 1988;525:363-74. doi: 10.1111/j.1749-6632.1988.tb38620.x.
The rat displays three behaviors when surface and/or deep body temperatures rise above their normal levels: grooming, which spreads saliva over the fur to cool by evaporation; locomotion, which results in escape to a cooler environment; and relaxed postural extension, which reduces heat production by muscle activity and increases heat dissipation by increasing body surface area. Each of these behaviors can be elicited in pure or nearly pure form by localized warming of thermosensors in different brain areas. In addition, localized warming of superficial and deep peripheral thermosensors elicits grooming and locomotion, but little or no postural extension. Because of the marked differences in the behaviors induced by localized warming of different sets of thermosensors, it is concluded that sensors are linked to the effector mechanisms for these behaviors by relatively separate and independent pathways rather than a master controller through which sensory signals are integrated to produce a unitary error signal that drives all responses. When more generalized hyperthermia in natural heat stress situations affects mainly superficial thermosensors, as during the initial phase of exposure to ambient heat, grooming and locomotion are predominant and extension is absent or weak. When deep hyperthermia is predominant and superficial hyperthermia is relatively weak, as occurs after escape from ambient heat to thermoneutrality or during and following exercise in a thermally neutral environment, the resulting predominant activation of deep sensors elicits marked postural extension, but little or no grooming or locomotion. When both superficial and deep sensors are hyperthermic, as in the later stages of exposure to ambient heat, all three behaviors are present, although locomotion is somewhat greater and grooming is somewhat less than during predominantly superficial hyperthermia, and extension is somewhat less than during predominantly deep hyperthermia. As a consequence, grooming is maximal during predominantly superficial hyperthermia, locomotion during mixed deep and superficial hyperthermia, and extension during predominantly deep hyperthermia. It is concluded that the relatively fractionated control of the rat's thermoregulatory behaviors by different groups of central and peripheral thermosensors makes possible a differentiation of responses to different distributions of hyperthermia between superficial and deep sensors that optimizes cost-benefit trade-offs in different kinds of heat stress.
当体表温度和/或深部体温升至正常水平以上时，大鼠会表现出三种行为：梳理毛发，即将唾液涂抹在皮毛上通过蒸发来降温；移动，即逃至较凉爽的环境；以及放松的姿势伸展，即通过减少肌肉活动产热并通过增加体表面积来增加散热。通过对不同脑区的温度感受器进行局部加热，这些行为中的每一种都可以以纯粹或近乎纯粹的形式被诱发出来。此外，对浅表和深部外周温度感受器进行局部加热会引发梳理毛发和移动行为，但姿势伸展很少或没有。由于不同组别的温度感受器局部加热所诱发的行为存在显著差异，因此可以得出结论，温度感受器是通过相对独立的途径与这些行为的效应机制相连，而不是通过一个主控制器，通过该主控制器整合感觉信号以产生驱动所有反应的单一误差信号。在自然热应激情况下，当更普遍的体温过高主要影响浅表温度感受器时，如在暴露于环境热的初始阶段，梳理毛发和移动行为占主导，而伸展行为不存在或较弱。当深部体温过高占主导且浅表体温过高相对较弱时，如从环境热中逃至热中性环境后或在热中性环境中运动期间及之后，由此导致的深部感受器的主要激活会引发明显的姿势伸展，但梳理毛发和移动行为很少或没有。当浅表和深部感受器都体温过高时，如在暴露于环境热的后期阶段，所有三种行为都会出现，尽管移动行为比主要为浅表体温过高时略多，梳理毛发行为略少，伸展行为比主要为深部体温过高时略少。因此，梳理毛发行为在主要为浅表体温过高时最为明显，移动行为在深部和浅表混合体温过高时最为明显，伸展行为在主要为深部体温过高时最为明显。可以得出结论，不同组别的中枢和外周温度感受器对大鼠体温调节行为的相对分散控制，使得对浅表和深部感受器之间不同热过高分布的反应能够有所区分，从而在不同类型的热应激中优化成本效益权衡。
