Thermosensitivity of rat's scrotum.

与其他皮肤感觉相比，温度感觉在神经生理学上没有很好的文献记载。这是因为传递皮肤温度信息的神经元数量很少。这种倾向在这种感觉的高级中继站，即脊髓、丘脑和大脑皮层变得更加强烈。1973年，Hellon发现，在大鼠的脊髓、背角和其他中枢神经系统中，有高密度的神经元对阴囊热刺激做出反应。此后，许多研究者将该系统作为热传入通路的模型进行研究。然而，最近，Kanosue等人。(1984,1985)发现这些神经元对阴囊温度变化本身没有反应，而且这种反应是伴随着EEG唤醒的非特异性反应。因此，在目前的研究中，我通过分析阴囊热刺激作为无条件刺激的操作行为，检查了大鼠是否真的“感觉”到了阴囊温度的变化。一只老鼠被放在一个小笼子里。阴囊上装有Pertier装置(5x5 Cm)，尾部周围放置一对电极，用于施加电击。首先将阴囊温度(T；lt；src&gt；)设置在32ﾟC的正常水平，然后逐步提高到42ﾟC，10秒后对尾部进行电击，T；lt；scr&gt；恢复到原来的低水平。如果大鼠按下杠杆，放在动物前面，他就可以避免电击，T；；Scr&gt；降低。我在11只大鼠身上测试了这种可操作性条件反射。不幸的是，没有老鼠学会这项任务。然而，仅从这一结果不能得出结论，即大鼠没有感觉到阴囊温度的变化，因为作为无条件刺激，刺激可能太弱了，尽管它感觉到了。

Temperature sensation is not well documented neurophysiologically as compared with other skin sensation. This is because number of neurons that convey informations of skin temperature is small. This tendency becomes stronger at higher relay station of this sensation; that is, spinal cord, thalamus, and cerebral cortex. In 1973 Hellon found that there are a high density of neurons in the spinal dorsal horn and other central nervous system that responded to thermal stimulation of the scrotum in rats. From later on, this system was studied by many investigators as a model of thermal afferent pathway. Recently, however, Kanosue et al. (1984, 1985) found that these neurons do not respond to scrotal temperature change itself and that the responses are nonspecific one which accompany EEG arousal. Therefore, in the present study I examined if rats really "feel" scrotal temperature change by analyzing operant behavior, in which scrotal thermal stimulation was used as an unconditioned stimulus. A rat was placed in a small cage. A Pertier device (5 x 5 cm) was attached to the scrotum and a pair of electrodes for applying an electrical shock were set around the tail. At first scrotal temperature (T_<src>) was set at normal level of 32ﾟC. Then, it was raised stepwisely to 42ﾟC and 10 sec later electrical shock was applied to the tail and T_<scr> was returned to the original low level. If the rat pressed a lever, setting in front of the animal, he could avoid the shock and T_<scr> was decreased. I tested this operant conditioning in eleven rats. Unfortunately, no rat learned this task. It can not be concluded only from this result, however, that the rat does not sense scrotal temperature change, because the stimulus might have been too week as an unconditioned stimulus, even though he sensed it.