丘脑是多种特异感觉的投射区。曾有人认为

丘脑是痛觉产生的重要结构基础。近年来有不少文献报道

丘脑后核(PO)与躯体痛觉的关系密切

但对PO与内脏痛觉的关系的报道却很少。内脏信息可通过迷走神经内脏大神经、盆神经以及其他分布于内脏的神经中的传人纤维传入中枢。但大多数人认为

内脏痛觉主要由内脏大神经中的传入纤维传导。关于内脏大神经传入纤维向丘脑的投射

很早就有人研究。1958年MeLeod报道了内脏大神经传入路在猫丘脑后腹核(VPL与VPM核)中存在代表区

其后于1972年Langenstein又发表了类似的报道

相继肯定了后腹核为内脏大神经传入路的丘脑代The thalamus is a part projected by many kinds of special sensation. Recently

a lot of literature reported that PO nucleus of the thalamus has close relation with pain sensation

but scarcely any materials concerning the function of PO on visceral pain were reported. Experiments were performed on 41 adult cats(2.0-3.9Kg body weight). After anaesthetized lightly with chloralose (60mg/Kg) intravenously

splanchnic nerve was separated extraperitoneally. The skull of the cat was fixed on the stereotaxic apparatus. The surface of the cerebrum was revealed in small area and sealed with agar. We drained the fourth ventricle to keep the cerebrospinal pressure stable. The cats were immobilized With flaxedil and the experiments were carried out under the condition of artificial re- spiration. By means of the stereotaxic apparatus a glass microelectrode (1-μ)was implanted into the PO nucleus of the thalamus. After ligating the efferent end of the splanchnic nerve

it was stimula- ted eith much stronger electric impulse to cause visceral pain. We found out 77 units which showed evoked discharges by stimulating the splanchnic nerve. Two clusters of discharges were found in 40 units of them and three clusters in ll of the total(77). The latent period of the Ist cluster of discharges is 43.4±8.0 msec and the 2nd and the 3rd ones are 257±53 msec

402±33.5 msec respectively. Either the pattern or the latent period of the discharges are quite dif- ferent from those studied by McLeod and Langenstein in VPL of the thal- amus. Therefore we suppose that PO nucleus might be one of two represent- ative areas of the splanchnic afferent path and it has relations with visc- eral sensation except somatic. Some inhibitory units were also seen in PO. The spontaneous dischar- ges of the neurons decrease and even cease as the splanchnic nerve is sti- mulated. The role of this inhibitory phenomenon requires further study.