Premotoneuronal inputs to early developing trigeminal motoneurons

Publication date: Available online 24 January 2017
Source:Journal of Oral Biosciences
Author(s): Keishi Matsuda, Shiro Nakamura, Mutsumi Nonaka, Ayako Mochizuki, Kiyomi Nakayama, Takehiko Iijima, Atsuro Yokoyama, Makoto Funahashi, Tomio Inoue
ObjectivesWe previously reported that masseter motoneurons (MMNs) and digastric motoneurons (DMNs) in postnatal day (P) 1–5 rats receive convergent inputs from the lateral (l-) and medial (m-) supratrigeminal regions (SupV), intertrigeminal region (IntV), and dorsal region of the principal sensory trigeminal nucleus (PrV). The l-SupV sends burst inputs predominantly to the MMNs. We compared the synaptic inputs to P9–12 rat MMNs and DMNs with those found in the previous study involving P1–5 rats.MethodsWe performed whole-cell recordings and laser photolysis of caged glutamate in the MMNs and DMNs of P9–12 rats.ResultsSimilar to P1–5 rats, the photostimulation of multiple regions within the l-SupV, m-SupV, IntV, and dorsal PrV, induced postsynaptic currents (PSCs) in both P9–12 MMNs and DMNs. Photostimulation induced predominantly low-frequency PSCs in both P9–12 motoneurons, whereas l-SupV photostimulation predominantly induced burst PSCs in P1–5 rats. However, when the caged glutamate concentration was doubled, l-SupV photostimulation evoked burst PSCs in all P9–12 MMNs. Furthermore, l-SupV and m-SupV photostimulation evoked burst or low-frequency PSCs at significantly higher rates in the MMNs compared to in the DMNs.ConclusionsThese results suggested that, similar to P1–5 motoneurons, both P9–12 motoneurons received convergent inputs from the SupV, IntV, and PrV; however, the input–output gains of some of the premotor neurons decreased. These synaptic input changes may contribute to the proper development of chewing.



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