| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1989: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1988: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
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.
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