title: Generation of resonance-dependent oscillation by mGluR-I activation switches single spiking to bursting in mesencephalic trigeminal sensory neurons.
abstract: The primary sensory neurons supplying muscle spindles of jaw-closing muscles are unique in that they have their somata in the mesencephalic trigeminal nucleus (MTN) in the brainstem, thereby receiving various synaptic inputs. MTN neurons display bursting upon activation of glutamatergic synaptic inputs while they faithfully relay respective impulses arising from peripheral sensory organs. The persistent sodium current (IN aP ) is reported to be responsible for both the generation of bursts and the relay of impulses. We addressed how IN aP is controlled either to trigger bursts or to relay respective impulses as single spikes in MTN neurons. Protein kinase C (PKC) activation enhanced IN aP only at low voltages. Spike generation was facilitated by PKC activation at membrane potentials more depolarized than the resting potential. By injection of a ramp current pulse, a burst of spikes was triggered from a depolarized membrane potential whereas its instantaneous spike frequency remained almost constant despite the ramp increases in the current intensity beyond the threshold. A puff application of glutamate preceding the ramp pulse lowered the threshold for evoking bursts by ramp pulses while chelerythrine abolished such effects of glutamate. Dihydroxyphenylglycine, an agonist of mGluR1/5, also caused similar effects, and increased both the frequency and impedance of membrane resonance. Immunohistochemistry revealed that glutamatergic synapses are made onto the stem axons, and that mGluR1/5 and Nav1.6 are co-localized in the stem axon. Taken together, glutamatergic synaptic inputs onto the stem axon may be able to switch the relaying to the bursting mode.
authors.affiliation: Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, Suita, Osaka, 565-0871, Japan; Pain Cognitive Function Research Center, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Gehoon
authors.initials: G
authors.lastname: Chung
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Saito
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kawano
authors.forename: Dongxu
authors.initials: D
authors.lastname: Yin
authors.forename: Soojung
authors.initials: S
authors.lastname: Lee
authors.forename: Mikihiko
authors.initials: M
authors.lastname: Kogo
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takada
authors.forename: Yong Chul
authors.initials: YC
authors.lastname: Bae
authors.forename: Joong Soo
authors.initials: JS
authors.lastname: Kim
authors.forename: Seog Bae
authors.initials: SB
authors.lastname: Oh
authors.forename: Youngnam
authors.initials: Y
authors.lastname: Kang
mesh_terms: D000200:Action Potentials; D000818:Animals; D018698:Glutamic Acid / Q000494:pharmacology / Q000502:physiology; D062557:NAV1.6 Voltage-Gated Sodium Channel / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000378:metabolism / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism; D013681:Tegmentum Mesencephali / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D062557:NAV1.6 Voltage-Gated Sodium Channel; D018094:Receptors, Metabotropic Glutamate; C507811:Scn8a protein, rat; D018698:Glutamic Acid; D011493:Protein Kinase C
keywords: burst firing; mesencephalic trigeminal nucleus; metabotropic glutamate receptor; persistent sodium current; primary sensory neurons