刺激视叶对脊髓活动的影响

实验在分析诱发VRP传入纤维类别的基础上,以DRP和VRP为指标,观察了牛蛙视叶下行冲动对脊髓活动的影响。发现:1、刺激坐骨神经诱发的脊髓VRP有早、晚两个成分;早期成分由Ⅰ、Ⅱ、Ⅲ类传入纤维兴奋引起;晚期成分由Ⅳ类传入纤维兴奋引起。2、刺激牛蛙视叶可诱发脊髓DRP。3、刺激视叶对刺激坐骨神经诱发的脊髓VRP早、晚期成分均有抑制作用。该抑制时程长,且早期成分的抑制和DRP在时程上有相关性。上述结果表明;视叶能以突触前抑制的形式参与躯体感觉传入的离心控制,影响脊髓反射活动,并可能涉及镇痛机制。

THE EFFECTS OF STIMULATING OPTIC TECTUM ON THE SPINAL ACTIVITY IN BULLFROG

By using dorsal root patientials (DRP) and ventral root patientials (VRP) as in dexes, the effects of descending volleys originating from the optic tectum on spinal activity were observed in bullfrogs. The experimental results obtained were as follows; 1.DRP was evoked by stimulation of the optic rectum. 2. VRP evoked by stimulation of the siatic nerve comsisted of two components. The early conponent was evoked chiefly by type Ⅰ and Ⅱ afferent fibers and also contributed by type Ⅲ fibers; the late one was evoked by type Ⅳ afferent fibers. 3. VRP evoked by stimulation of the siatic nerve was inhibited by stimulation of the optic tectum. The duration of inhibition of the early component was related to that of DRP. Thus, the results indicate that the optic tectum takes part in the centrifugal control of somatosensory afferent activity, affects the spinal reflex, and involves in the mechanism of analgesia by way of presynaptic inhibition.