Watson Alan H D, Hughes David I, Bazzaz Ayoub A
School of Biosciences, University of Wales Cardiff, Cardiff CF10 3US, Wales, United Kingdom.
J Comp Neurol. 2002 Oct 28;452(4):367-80. doi: 10.1002/cne.10410.
gamma-Aminobutyric acid (GABA) and glycine have been implicated in the inhibition of sensory pathways in the dorsal horn of the spinal cord. The object of this study is to investigate the interactions between neurones immunoreactive for GABA and/or glycine and hair follicle afferent terminals labelled by intracellular injection with neurobiotin. GABA and glycine-like immunoreactivity in axons and dendrites in synaptic contact with the afferent terminals was demonstrated by using a postembedding immunogold method, and serial section reconstruction was used to show the distribution and nature of these interactions in lamina III of the dorsal horn. Most afferent boutons (94%) were postsynaptic at axo-axonic synapses: 67% of presynaptic boutons presynaptic to the afferent terminals were immunoreactive for GABA and glycine, 24% for GABA alone, and 7% for glycine alone. Only a small percentage of dendrites postsynaptic to afferent boutons appeared to belong to inhibitory interneurones: 3% were immunoreactive for GABA and glycine, 10% for glycine alone, but 87% were immunoreactive for neither antibody. Many afferent boutons were the central terminals of what appeared to be type IIb glomeruli and were involved triadic synaptic arrangements at which boutons presynaptic to an afferent terminal also made axodendritic contacts with dendrites postsynaptic to the afferent. Many of the presynaptic boutons involved in the triads were immunoreactive for GABA and glycine. Because afferent terminals do not themselves express glycine receptors (Mitchell et al. [1993] J. Neurosci. 13:2371-2381), glycine may therefore act on dendrites postsynaptic to hair follicle afferent terminals at these triads.
γ-氨基丁酸（GABA）和甘氨酸与脊髓背角感觉通路的抑制作用有关。本研究的目的是调查对GABA和/或甘氨酸免疫反应的神经元与通过细胞内注射神经生物素标记的毛囊传入终末之间的相互作用。通过包埋后免疫金法显示与传入终末形成突触接触的轴突和树突中的GABA和甘氨酸样免疫反应性，并使用连续切片重建来显示背角III层中这些相互作用的分布和性质。大多数传入终扣（94%）在轴-轴突触处为突触后：在传入终末之前的突触前终扣中，67%对GABA和甘氨酸呈免疫反应，24%仅对GABA呈免疫反应，7%仅对甘氨酸呈免疫反应。传入终扣突触后的树突中只有一小部分似乎属于抑制性中间神经元：3%对GABA和甘氨酸呈免疫反应，10%仅对甘氨酸呈免疫反应，但87%对两种抗体均无免疫反应。许多传入终扣是IIb型小球的中枢终末，并参与三联突触排列，在这种排列中，传入终末之前的终扣也与传入终末突触后的树突形成轴-树突接触。参与三联体的许多突触前终扣对GABA和甘氨酸呈免疫反应。由于传入终末本身不表达甘氨酸受体（Mitchell等人，[1993]《神经科学杂志》13:2371 - 2381），因此甘氨酸可能在这些三联体处作用于毛囊传入终末突触后的树突。
