Morphological analysis of limbic modulation of descending pain inhibitory system

为了了解边缘结构如何影响下行抗伤害性感觉系统，我们研究了下丘脑和杏仁核终末是否与中脑导水管周围灰质(PAG)的头端延髓腹内侧部(RVM)投射神经元进行突触接触。结果发现，下丘脑腹内侧轴突和RVM投射神经元在PAG的外侧/背内侧有明显的重叠分布。此外，电子显微镜观察发现，下丘脑腹内侧神经末梢与投射RVM的PAG神经元有不对称的突触接触。我们进一步证明，大多数RVM投射的PAG神经元均为囊泡型谷氨酸转运体2mRNA阳性，提示这些神经元是谷氨酸能神经元。

To understand how limbic structures influence descending antinociceptive system, we examined whether hypothalamic and amygdaloid terminals make synaptic contact with rostral ventromedial medulla (RVM)-projecting neurons in the periaqueductal gray (PAG). As a result, prominent overlapping distribution of the ventromedial hypothalamic axons and RVM-projecting neurons was observed in the lateral/dorsomedial part of the PAG. Furthermore, electron microscopic observation revealed that ventromedial hypothalamic terminals made asymmetrical synaptic contactswith RVM-projecting PAG neurons. We further demonstrated that most of the RVM-projecting PAG neurons are positive for vesicular glutamate transporter 2 mRNA, suggesting that these neurons are glutamatergic.