关键词：
optical mapping
trigeminal nucleus
functional organization
development
synaptic connections
chick embryo
摘要：
The functional organization of the trigeminal nuclei during embryogenesis was investigated using multiple-site optical recording with a fast voltage-sensitive dye. Brainstem preparations, with three classified trigeminal nerve afferents, the ophthalmic, maxillary and mandibular nerves, together with motor nerve fibers, were dissected from five- to eight-day-old chick embryos. Electrical responses evoked by trigeminal nerve stimulations were optically recorded simultaneously from many loci of the stained preparations. We identified three response areas related to the trigeminal nerve: area I, located cephalic to the level of the trigeminal ganglion;area II, located caudal to the level of the trigeminal ganglion;and area III, located at the level of the trigeminal root. The neural responses in areas I and II were evoked by ophthalmic, maxillary or mandibular nerve stimulation, while the responses in area In were detected when the stimulation was applied to the trigeminal motor nerve. In comparison with the morphology indicated by DiI labeling, the results suggest that areas I, II and In correspond to the principal sensory nucleus of the trigeminal nerve, the spinal sensory nucleus of the trigeminal nerve and the trigeminal motor nucleus, respectively. We identified two components of the optical response: a fast and a slow signal. In five-day-old preparations, fast spike-like signals related to action potentials were recorded from the three response areas. In six-day-old preparations, slow optical signals which reflect glutamate-mediated excitatory postsynaptic potentials were detected from area II, only when the ophthalmic nerve was stimulated: no slow signal was evoked by maxillary or mandibular nerve stimulation In seven- and eight-day-old preparations, slow signals were detected from both areas I and II with every nerve stimulation. These results suggest that synaptic function is first generated in the spinal trigeminal nucleus by the six-day embryonic stage, and t
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