Behbehani M M, Fields H L
Brain Res. 1979 Jul 6;170(1):85-93. doi: 10.1016/0006-8993(79)90942-9.
Both electrical stimulation and injection of morphine into the midbrain periaqueductal gray (PAG) produce analgesia in the rat. There is evidence that this analgesic effect is mediated by a descending system that involves nucleus raphe magnus (NRM) and adjacent reticular formation. In the studies reported here, the activity of the cells in the PAG was increased by microinjection of glutamate in this area and its effect on both the activity of single cells in the NRM and on a flexion reflex elicited by noxious heat was measured. It is shown that an increase in the firing rate of the cells in the PAG is associated with a raised threshold for flexion and is also correlated with an increase in the firing rate of a majority of the cells in the NRM. This effect on the flexion reflex can be abolished by (a) lesion of the nucleus raphe magnus and a small area of the reticular formation surrounding this nucleus and (b) by nalazone 20 min after its i.v. injection. It is concluded that there is an excitatory connection between the periaqueductal gray and the nucleus raphe magnus and that activation of this system can cause analgesia.
电刺激和向大鼠中脑导水管周围灰质（PAG）注射吗啡均可产生镇痛作用。有证据表明，这种镇痛作用是由一个下行系统介导的，该系统涉及中缝大核（NRM）和相邻的网状结构。在本文报道的研究中，通过向该区域微量注射谷氨酸来增加PAG中细胞的活性，并测量其对NRM中单个细胞活性以及对有害热引起的屈肌反射的影响。结果表明，PAG中细胞放电频率的增加与屈肌反射阈值的升高相关，并且还与NRM中大多数细胞的放电频率增加相关。对屈肌反射的这种影响可通过以下方式消除：（a）损毁中缝大核以及围绕该核的一小片网状结构区域；（b）静脉注射纳洛酮20分钟后。得出的结论是，导水管周围灰质与中缝大核之间存在兴奋性联系，并且该系统的激活可导致镇痛。
