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This Article Full Text Full Text (PDF) All Versions of this Article: 100/4/1885    most recent 01145.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nakamura, S. Articles by Maki, K. PubMed PubMed Citation Articles by Nakamura, S. Articles by Maki, K.

Synaptic Transmission From the Supratrigeminal Region to Jaw-Closing and Jaw-Opening Motoneurons in Developing Rats

¹Department of Oral Physiology and ²Department of Orthodontics, Showa University School of Dentistry, Tokyo; and ³Department of Oral Anatomy and Neurobiology, Faculty of Dentistry, Osaka University, Osaka, Japan

Submitted 17 October 2007; accepted in final form 22 August 2008

The supratrigeminal region (SupV) receives abundant orofacial sensory inputs and descending inputs from the cortical masticatory area and contains premotor neurons that target the trigeminal motor nucleus (MoV). Thus it is possible that the SupV is involved in controlling jaw muscle activity via sensory inputs during mastication. We used voltage-sensitive dye, laser photostimulation, patch-clamp recordings, and intracellular biocytin labeling to investigate synaptic transmission from the SupV to jaw-closing and jaw-opening motoneurons in the MoV in brain stem slice preparations from developing rats. Electrical stimulation of the SupV evoked optical responses in the MoV. An antidromic optical response was evoked in the SupV by MoV stimulation, whereas synaptic transmission was suppressed by substitution of external Ca²⁺ with Mn²⁺. Photostimulation of the SupV with caged glutamate evoked rapid inward currents in the trigeminal motoneurons. Gramicidin-perforated and whole cell patch-clamp recordings from masseter motoneurons (MMNs) and digastric motoneurons (DMNs) revealed that glycinergic and GABAergic postsynaptic responses evoked in MMNs and DMNs by SupV stimulation were excitatory in P1–P4 neonatal rats and inhibitory in P9–P12 juvenile rats, whereas glutamatergic postsynaptic responses evoked by SupV stimulation were excitatory in both neonates and juveniles. Furthermore, the axons of biocytin-labeled SupV neurons that were antidromically activated by MoV stimulation terminated in the MoV. Our results suggest that inputs from the SupV excite MMNs and DMNs through activation of glutamate, glycine, and GABA_A receptors in neonates, whereas glycinergic and GABAergic inputs from the SupV inhibit MMNs and DMNs in juveniles.