Optical survey of initial expression of synaptic function in the embryonic chick trigeminal sensory nucleus.
We examined the initial expression of synaptic function in the embryonic chick trigeminal nucleus using voltage-sensitive dye recording. Brainstem preparations with three trigeminal nerve afferents, the ophthalmic nerve (N.V1), maxillary nerve (N.V2) and mandibular nerve (N.V3), were dissected from 5.5- to 6.5-day-old chick embryos. In our previous study [Sato et al., 1999], we detected slow signals corresponding to glutamatergic excitatory postsynaptic potentials and identified the principal sensory nucleus of the trigeminal nerve (Pr5), spinal sensory nucleus of the trigeminal nerve (Sp5) and trigeminal motor nucleus. In this study, we examined the effects of removing Mg(2+) from the physiological solution, which enhanced N-methyl-d-aspartate receptor function in the sensory nuclei. In 6.5-day-old (St 29) embryos, the slow signal was observed in Pr5 and Sp5 only when N.V1 was stimulated, whereas it appeared in Mg(2+)-free solution with every nerve stimulation. In 6-day-old (St 28) embryos, the slow signal was observed in Sp5 with N.V1 stimulation, and the appearance of synaptic function in Mg(2+)-free solution varied, depending on the nerves and preparations used. In 5.5-day-old (St 27) embryos, synaptic function was not detected even when external Mg(2+) was removed. These results indicate that the initial expression of synaptic function in the trigeminal system occurs earlier than previously considered, and that the developmental organization of synaptic function differs among the three trigeminal nerves and between the two sensory nuclei.
Department of Health and Nutrition, Kanto Gakuin University, College of Human and Environmental Studies, Yokohama 236-8503, Japan. Electronic address: katsu-satoh@komajo.ac.jp.
Yoko
Y
Momose-Sato
Department of Health and Nutrition Sciences, Komazawa Women's University Faculty of Human Health, Tokyo 206-8511, Japan.
Katsushige
K
Sato
D000818:Animals; D002413:Cations, Divalent; D002642:Chick Embryo; D003470:Culture Media; D008274:Magnesium / Q000378:metabolism; D008340:Mandibular Nerve / Q000502:physiology*; D008442:Maxillary Nerve / Q000502:physiology*; D009882:Ophthalmic Nerve / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000502:physiology*; D014279:Trigeminal Nucleus, Spinal / Q000502:physiology
D002413:Cations, Divalent; D003470:Culture Media; D016194:Receptors, N-Methyl-D-Aspartate; D008274:Magnesium
Development; Optical recording; Synaptogenesis; Trigeminal nucleus; Voltage-sensitive dye