Impulse Trafficking in Neurons of the Mesencephalic Trigeminal Nucleus

Saito, Mitsuru,Kang, Young-Nam The Korean Academy of Oral Biology 2006 International Journal of Oral Biology Vol.31 No.4

In the primary sensory neuron of the mesencephalic trigeminal nucleus (MTN), the peripheral axon supplies a large number of annulospiral endings surrounding intrafusal fibers encapsulated in single muscle spindles while the central axon sends only a few number of synapses onto single ${\alpha}-motoneurons({\alpha}-MNs)$. Therefore, the ${\alpha}-{\gamma}$ linkage is thought to be very crucial in the jaw-closing movement. Spike activity in a ${\gamma}-motoneuron\;({\gamma}-MN)$ would induce a large number of impulses in single peripheral axons by activating many intrafusal fibers simultaneously, subsequently causing an activation of ${\alpha}-MNs$ in spite of the small number of synapses. Thus, the activity of ${\gamma}-MNs$ may be vital for modulation of jaw-closing movements. Independently of such a spindle activity modulated by ${\gamma}-MNs$, somatic depolarization in MTN neurons is known to trigger the oscillatory spike activity. Nevertheless, the trafficking of these spikes arising from the two distinct sources of MTN neurons is not well understood. In this short review, switching among multiple functional modes of MTN neurons is discussed. Subsequently, it will be discussed which mode can support the ${\alpha}-{\gamma}$ linkage. In our most recent study, simultaneous patch-clamp recordings from the soma and axon hillock revealed a spike-back-propagation from the spike-initiation site in the stem axon to the soma in response to a somatic current pulse. The persistent $Na^+$ current was found to be responsible for the spike-initiation in the stem axon, the activation threshold of which was lower than those of soma spikes. Somatic inputs or impulses arising from the sensory ending, whichever trigger spikes in the stem axon first, would be forwarded through the central axon to the target synapse. We also demonstrated that at hyperpolarized membrane potentials, 4-AP-sensitive $K^+$ current ($IK_{4-AP}$) exerts two opposing effects on spikes depending on their origins; the suppression of spike initiation by increasing the apparent electrotonic distance between the soma and the spike-initiation site, and the facilitation of axonal spike invasion at higher frequencies by decreasing the spike duration and the refractory period. Through this mechanism, the spindle activity caused by ${\gamma}-MNs$ would be safely forwarded to ${\alpha}-MNs$. Thus, soma spikes shaped differentially by this $IK_{4-AP}$ depending on their origins would reflect which one of the two inputs was forwarded to the target synapses.

Regulation of blood pressure and sympathetic nerve activity during exercise in humans-muscle metaboreflex and arterial baroreflex function-

( Takeshi Nishiyasu ),( Mitsuru Saito ),( Narihiko Kondo ),( Masashi Ichinose ) 대한운동사협회 2008 대한운동사협회 운동사대회자료집 Vol.2008 No.-

Inhibition of GluR Current in Microvilli of Sensory Neurons via Na ⁺ -Microdomain Coupling Among GluR, HCN Channel, and Na ⁺ /K ⁺ Pump

Kawasaki, Yasuhiro,Saito, Mitsuru,Won, Jonghwa,Bae, Jin Young,Sato, Hajime,Toyoda, Hiroki,Kuramoto, Eriko,Kogo, Mikihiko,Tanaka, Takuma,Kaneko, Takeshi,Oh, Seog Bae,Bae, Yong Chul,Kang, Youngnam Frontiers Media S.A. 2018 Frontiers in cellular neuroscience Vol.12 No.-

<P>Glutamatergic dendritic EPSPs evoked in cortical pyramidal neurons are depressed by activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels expressed in dendritic spines. This depression has been attributed to shunting effects of HCN current (<I>I</I><SUB>h</SUB>) on input resistance or <I>I</I><SUB>h</SUB> deactivation. Primary sensory neurons in the rat mesencephalic trigeminal nucleus (MTN) have the somata covered by spine-like microvilli that express HCN channels. In rat MTN neurons, we demonstrated that <I>I</I><SUB>h</SUB> enhancement apparently diminished the glutamate receptor (GluR) current (<I>I</I><SUB>GluR</SUB>) evoked by puff application of glutamate/AMPA and enhanced a transient outward current following <I>I</I><SUB>GluR</SUB> (OT-<I>I</I><SUB>GluR</SUB>). This suggests that some outward current opposes inward <I>I</I><SUB>GluR</SUB>. The <I>I</I><SUB>GluR</SUB> inhibition displayed a U-shaped voltage-dependence with a minimal inhibition around the resting membrane potential, suggesting that simple shunting effects or deactivation of <I>I</I><SUB>h</SUB> cannot explain the U-shaped voltage-dependence. Confocal imaging of Na<SUP>+</SUP> revealed that GluR activation caused an accumulation of Na<SUP>+</SUP> in the microvilli, which can cause a negative shift of the reversal potential for <I>I</I><SUB>h</SUB> (<I>E</I><SUB>h</SUB>). Taken together, it was suggested that <I>I</I><SUB>GluR</SUB> evoked in MTN neurons is opposed by a transient decrease or increase in standing inward or outward <I>I</I><SUB>h</SUB>, respectively, both of which can be caused by negative shifts of <I>E</I><SUB>h</SUB>, as consistent with the U-shaped voltage-dependence of the <I>I</I><SUB>GluR</SUB> inhibition and the OT-<I>I</I><SUB>GluR</SUB> generation. An electron-microscopic immunohistochemical study revealed the colocalization of HCN channels and glutamatergic synapses in microvilli of MTN neurons, which would provide a morphological basis for the functional interaction between HCN and GluR channels. Mathematical modeling eliminated the possibilities of the involvements of <I>I</I><SUB>h</SUB> deactivation and/or shunting effect and supported the negative shift of <I>E</I><SUB>h</SUB> which causes the U-shaped voltage-dependent inhibition of <I>I</I><SUB>GluR</SUB>.</P>

A distinct functional distribution of α and γ motoneurons in the rat trigeminal motor nucleus

Morita-Isogai, Yukako,Sato, Hajime,Saito, Mitsuru,Kuramoto, Eriko,Yin, Dong Xu,Kaneko, Takeshi,Yamashiro, Takashi,Takada, Kenji,Oh, Seog Bae,Toyoda, Hiroki,Kang, Youngnam Springer-Verlag 2017 BRAIN STRUCTURE AND FUNCTION Vol.222 No.7

<P>Gamma-motoneurons (gamma MNs) play a crucial role in regulating isometric muscle contraction. The slow jaw-closing during mastication is one of the most functional isometric contractions, which is developed by the rank-order recruitment of alpha-motoneurons (alpha MNs) in a manner that reflects the size distribution of alpha MNs. In a mouse spinal motor nucleus, there are two populations of small and large MNs; the former was identified as a population of gamma MNs based on the positive expression of the transcription factor estrogen-related receptor 3 (Err3) and negative expression of the neuronal DNA-binding protein NeuN, and the latter as that of alpha MNs based on the opposite pattern of immunoreactivity. However, the differential identification of alpha MNs and gamma MNs in the trigeminal motor nucleus (TMN) remains an assumption based on the size of cell bodies that were retrogradely stained with HRP. We here examined the size distributions of alpha MNs and gamma MNs in the dorsolateral TMN (dl-TMN) by performing immunohistochemistry using anti-Err3 and anti-NeuN antibodies. The dl-TMN was identified by immunopositivity for vesicular glutamate transporter-1. Immunostaining for choline acetyltransferase and Err3/NeuN revealed that the dl-TMN is composed of 65% alpha MNs and 35% gamma MNs. The size distribution of alpha MNs was bimodal, while that of gamma MNs was almost the same as that of the population of small alpha MNs , suggesting the presence of alpha MNs as small as gamma MNs. Consistent with the size concept of motor units, the presence of smaller jaw-closing alpha MNs was coherent with the inclusion of jaw-closing muscle fibers with smaller diameters compared to limb muscle fibers.</P>

Associations of Serum Isoflavone, Adiponectin and Insulin Levels with Risk for Epithelial Ovarian Cancer: Results of a Case-control Study

Otokozawa, Seiko,Tanaka, Ryoichi,Akasaka, Hiroshi,Ito, Eiki,Asakura, Sumiyo,Ohnishi, Hirofumi,Saito, Shigeyuki,Miura, Tetsuji,Saito, Tsuyoshi,Mori, Mitsuru Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.12

Background: The aim of this study was to examine the association of serum isoflavones, adiponectin, and insulin levels with ovarian cancer risk. Materials and Methods: We gathered cases with histologically confirmed epithelial ovarian cancer at Sapporo Medical University Hospital from October 2010 to September 2012. Potential controls were recruited from female inpatients without any history of cancer or diabetes mellitus in different wards of the same hospital over the same period of time. Serum isoflavones, adiponectin, and insulin levels were measured in order to estimate associations with ovarian cancer risk in a case-control study. Data from 71 cases and 80 controls were analyzed with a logistic regression model adjusting for known risk factors. Results: A significant reduction in ovarian cancer risk was observed for the high tertile of serum daidzein level versus the low ($P_{trend}<0.001$). A significant reduction in ovarian cancer risk was also observed for the high tertile of serum glycitein level versus the low ($P_{trend}=0.005$). Furthermore, a significant reduction in ovarian cancer risk was observed for the high tertile of serum adiponectin level versus the low ($P_{trend}=0.004$). Conversely, serum insulin level showed significantly elevated risk for ovarian cancer with the high tertile versus the low $P_{trend}<0.001$). Conclusions: Decreased serum isoflavones levels, such as those for daidzein and glycitein, decreased serum adiponectin levels, and increased serum insulin levels could be shown to be associated with elevated risk of ovarian cancer.

High Speed and Sensitive X-ray Analysis System with Automated Aberration Correction Scanning Transmission Electron Microscope

Inada, Hiromi,Hirayama, Yoichi,Tamura, Keiji,Terauchi, Daisuke,Namekawa, Ryoji,Shichiji, Takeharu,Sato, Takahiro,Suzuki, Yuya,Ohtsu, Yoshihiro,Watanabe, Keitaro,Konno, Mitsuru,Tanaka, Hiroyuki,Saito, Korean Society of Microscopy 2015 Applied microscopy Vol.45 No.1

We have developed a new HD-2700 (Hitachi High-Technologies Corp., Japan) scanning transmission electron microscope (STEM) that includes an automatic aberration correction function, and a large-solid-angle energy-dispersive X-ray spectroscopy detector that enables high-resolution and sensitive analysis. For observation with atomic resolution, using spherical-aberration-corrected STEM, in order that satisfactory performance of the device can be achieved readily, and within a short time, irrespective of the operator's skill level, a spherical-aberration-correction device with an automatic aberration-correction function was developed. This automatic aberration-correction function carries out the entire correction-related process (aberration measurement, selection and correction) automatically, with automatic selection of the aberrations that require correction, and automatic measurement of the appropriate corrections.