Toshiki Murakami

Intracellular potential of medullary reticular neurons during sleep and wakefulness.

Abstract Intracellular records were obtained in the chronic cat from neurons of the nucleus reticularis gigantocellularis (NGC) during naturally occurring sleep and wakefulness. When wakefulness and quiet sleep was compared with active sleep, the membrane potential level of NGC neurons gradually decreased; a depolarized membrane potential was maintained tonically and selectively throughout active sleep. These data support the concept that NGC neurons assist in the generation of somatic atonia during active sleep and suggest that this state-dependent inhibitory function may be controlled by the nucleus pontis oralis as part of the general phenomenon of reticular response reversal.

Reflex responses of single salivatory neurons to stimulation of trigeminal sensory branches in the cat.

Responses of 71 single salivatory neurons, identified by antidromic spikes evoked by stimulation of the chorda tympani, were tested to stimulation of the ipsilateral infraorbital (IO), inferior alveolar (IA) and lingual nerves (LN) in the cat. Fifty-one neurons responded with spike potentials to stimulation of one or more of these nerves (responsive type, R), while the remaining 20 neurons did not respond to stimulation of any of them (non-responsive type, NR). Thirty-three R neurons were activated by stimulation of all of the 3 trigeminal afferent branches, while 12 neurons responded with spikes to stimulation of only one branch, usually of LN. Reflex spike responses appeared with a latency of 5.6-14.6 ms to LN stimulation, 6.4-15.7 ms to IO stimulation and 6.0-26.0 ms to IA stimulation. Impulses of both A beta and A delta afferent fibres of the trigeminal nerve were found to be effective for activation of salivatory neurons.

Responses of inferior salivatory neurons to stimulation of trigeminal sensory branches.

A total of 84 single inferior salivatory neurons was identified by antidromic stimulation of the tympanic nerve. Their responsiveness was tested to stimulation of the ipsilateral infraorbital, lingual, and inferior alveolar nerves in urethane-chloralose-anesthetized cats. The conduction velocities of preganglionic fibers of inferior salivatory neurons ranged from 2.2 to 9.1 m/s, and 54% of those neurons responded with spikes to stimulation of at least one of the infraorbital, lingual, or inferior alveolar nerves (responsive type neurons). The latencies of spike responses to stimulation of the trigeminal sensory branches ranged from 4.0 to 21.0 ms, which were shorter than those of superior salivatory neurons. Impulses of both A-beta and A-delta afferent fibers of the trigeminal nerve were found to be effective for activation of inferior salivatory neurons. The convergence of excitatory inputs from more than one sensory nerve was found in most of the responsive type neurons (73%).

Antidromic responses and reflex activity of single salivatory neurons in the cat.

Abstract Single salivatory neurons of the brain stem of the urethane-chloralose anesthetized cat were identified by their antidromic responses to stimulation of the chorda tympani. The antidromically identified neurons were recorded in the lateral reticular formation of the brain stem between the spinal trigeminal nucleus and the vestibular complex. As suggested by previous anatomic work, the salivatory neurons appear to be diffusely distributed within the region. The identified neurons responded synaptically to stimulation of the lingual nerve, but this reflex activity was not mediated by an input from the taste fibers.

Effects of neck muscle activities during rhythmic jaw movements by stimulation of the medial vestibular nucleus

s / Neuroscience Research 71S (2011) e108–e415 e245 APAs were also retained for three months. These results suggest the involvement of the central nervous system in controlling postural muscle activities and improving performance. Research fund: KAKENHI (21700517 and 20500436). doi:10.1016/j.neures.2011.07.1068 P3-h11 Effects of neck muscle activities during rhythmic jaw movements by stimulation of the medial vestibular nucleus Yoshihide Satoh 1 , Eriko Yajima 2, Yasuhiro Nagamine 2, Ken’Ichi Ishizuka 1, Toshiki Murakami 1 1 Dept. of Physiol., Sch. of Life Dent. at Niigata, Nippon Dent. Univ., Niigata, Japan 2 Dept. of Orthodon., Sch. of Life Dent. at Niigata, Nippon Dent. Univ., Niigata, Japan The medial vestibulospinal tract originates from the medial vestibular nucleus (MVN) descends to the cervical anterior cord and are involved in control of the vestibulo-collic reflex. Our previous paper showed that cortically induced rhythmic jaw movements were modulated by stimulation of the MVN. Head movements are reported to occur concomitantly with jaw movements. It has been suggested that these coordinated movements take place to smooth jaw movements and balance the trunk. It is therefore likely that the MVN is involved in control of head and jaw movements during rhythmic jaw movements. This study first examines whether there is rhythmic activity of the neck muscles during cortically induced rhythmic jaw movements in rats anesthetized by urethane. Rhythmic jaw movements were induced by repetitive electrical stimulation of the orofacial motor cortex (0.5 ms duration, 30 Hz, 10 s). An electromyogram in the splenius muscles (spEMG) showed rhythmic bursts during the jaw-opening phase. In the sternomastoid (stEMG), however, the electromyogram did not show any bursts during rhythmic jaw movements. A further study then examines whether stimulation of the medial vestibular nucleus (MVN) modulates the rhythmic activity of the neck muscles. Electrical stimulation (0.3 ms duration, 1 Hz, 130 A, 4 s) was applied to the MVN 6 s after the beginning of stimulation of the orofacial motor cortex. Stimuli applied in the jaw-closing phase induced a transient burst in the stEMG, and the duration of activity in the spEMG was increased. Stimuli applied in the jaw-opening phase induced a transient burst in the stEMG and an inhibitory period in the spEMG. These results imply that the MVN is involved in the modulation of neck muscle activities during rhythmic jaw movements induced by stimulating the orofacial motor cortex. Research fund: KAKENHI 22592079. doi:10.1016/j.neures.2011.07.1069 P3-h12 Search for interneurons that regulate larval locomotion in Drosophila Yuki Itakura 1 , Hiroshi Kohsaka 2, Akinao Nose 1,2 1 Dept of Complexity Sci and Eng, Grad Sch of Frontier Sci, Univ of Tokyo, Kashiwa, Japan 2 Dept of Physics, Grad Sch of Science Univ of Tokyo, Tokyo, Japan Muscles and motoneurons, central neurons, and peripheral sensory neurons all have distinct important functions in coordinating locomotion. To reveal how the neural network underlying locomotion functions, it is necessary to understand the functional principle of each component. Whereas muscles, motoneurons and sensory neurons are well investigated, far less is known about interneurons that generate motor patterns. We use the Drosophila motor circuits underlying larval crawling as a model to identify such interneurons and try to elucidate the operational principle of the motor circuits. Here we searched for GAL4 lines expressing GAL4 in specific interneurons that form potential synaptic contacts with motor neurons, by using GRASP, a split-GFP system that visualizes membrane adjacency between two cells. In one of the GAL4 lines identified, a GRASP signal was observed in the neuropile regions that are known to be targeted by the dendrites of motor neurons. Anatomical analyses showed that in abdominal segments the GAL4 expression in this line is largely confined to a class of interneuron (1 cell per hemisegment) whose cell bodies are located in the ventral region of the nerve cord and which extends neurites ipsilaterally to the dorsal neuropile regions occupied by dendrites of motoneurons. Calcium imaging with a genetically encoded calcium sensor G-CaMP expressed by the GAL4 line revealed a wave of neural activities that propagates from posterior to anterior segments in a similar pattern to the activity propagation of motor neurons. These observations suggest that the interneurons identified by the GAL4 line are upstream neurons that drive or modulate the activity of motor neurons. We are now performing more detailed anatomical analyses of the connectivity of these neurons as well as functional analyses of the role of these neurons with optogenetics. doi:10.1016/j.neures.2011.07.1070 P3-h13 Spontaneous depolarization wave in the embryonic mouse CNS: Disappearance of the wave with development and its mechanism Yoko Momose-Sato 1,3 , Tomoharu Nakamori 2,3, Katsushige Sato 2,3 1 Department of Health and Nutrition, College of Human Environmental Studies, Kanto-Gakuin University, Yokohama 2 Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women’s University, Tokyo 3 Human Frontier Science Program During development, correlated neuronal activity plays an important role in the establishment of the nervous system. Using an optical imaging technique with voltage-sensitive dyes, we previously reported a large-scale correlated wave activity, termed the depolarization wave, in the chick, rat, and mouse embryos. In the present study, we examined developmental changes in the depolarization wave in the mouse embryo, especially the change in its spatial distribution. Brainstem-whole spinal cord preparations were dissected from E11–E14 mouse embryos, and optical signals were recorded together with the electrical discharges of cranial and spinal motoneurons. Spontaneous optical signals that appeared in association with the rhythmic motoneuronal discharges spread like a wave over the brainstem and spinal cord at E11–E13, while the signals were localized in the rostrolateral medulla and lumbosacral cord at E14. Application of a GABAA receptor antagonist bicuculline and a glycine receptor antagonist strychnine transformed the localized activity at E14 into a synchronized wave by augmenting the amplitude and spatial extent of the activity. In addition, a nACh receptor antagonist d-tubocurarine exhibited a similar effect. At E11–E12, these blockers inhibited the depolarization wave, suggesting that developmental changes in pharmacological natures of the network, including the switching of GABAergic/glycinergic responses from excitation to inhibition, might underlie the spatial segregation of the depolarization wave observed at E14. doi:10.1016/j.neures.2011.07.1071 P3-h14 Screening of voltage-sensitive fluorescence dyes for imaging embryonic neural activity Katsushige Sato 1,3 , Ryo Komuro 2, Tomoharu Nakamori 1,3, Yoko Momose-Sato 2,3 1 Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women’s University, Tokyo 2 Department of Health and Nutrition, College of Human Environmental Studies, Kanto-Gakuin University, Yokohama 3 Human Frontier Science Program Using the optical imaging technique with voltage-sensitive dyes, we have investigated functional organization and architecture of the embryonic central nervous system (CNS). Among the voltage-sensitive absorption dyes, NK2761, a merocyanine-rhodanine dye, is the most useful for detecting neural activity because of the high signal-to-noise ratio, low toxicity and small dye bleaching. On the other hand, voltage-sensitive fluorescence dyes are thought to be good candidates for optically detecting transmembrane voltage changes at the cellular level. Here, we evaluated the suitability of a variety of fast voltage-sensitive fluorescence dyes for optical recording in the embryonic CNS. We screened some styryl dyes in isolated brainstem preparations from 7-day old chick embryos. Measurements of voltage-related optical signals were made using a multiple-site optical recording system. The signal size, signal-to-noise ratio, photobleaching, and effects of perfusion were examined. Although fluorescence dye signals had lower signal-to-noise ratio than those of absorption dyes, we could detect neural activity with voltagesensitive fluorescence dyes. doi:10.1016/j.neures.2011.07.1072

Effects of the vestibular nucleus stimulation on the masseteric monosynaptic reflex

s S201 the properties of the activity propagation more in detail by pharmacological and anatomical approach. doi:10.1016/j.neures.2009.09.1096 P3-a27 Motor functions of dopamine D2 receptor-expressing neurons in the striatum Hiromi Sano1, Satomi Chiken1, Kazuto Kobayashi2, Atsushi Nambu1 1 Division of System Neurophysiology, National Institute for Physiological Sciences, Okazaki, Japan; 2 Department of Molecular Genetics, Fukushima Med. University, Fukushima, Japan Dopamine D2 receptors (D2R) are expressed in the striatopallidal neurons and the cholinergic interneurons in the striatum. By using immunotoxin-mediated cell targeting, ablation of D2R-expressing neurons in the striatum increased spontaneous motor activity in mice. To investigate the mechanism of motor hyperactivity of these mice, we record neuronal activity of the globus pallidus (GP) and substantia nigra pars reticulata (SNr) in the awake state. Motor cortical stimulation induces triphasic responses composed of early excitation, inhibition and late excitation in the GP and SNr of wild-type mice. In contrast, cortically evoked inhibition is diminished in the GP of transgenic mice, whereas triphasic responses are well preserved in the SNr. Motor functions of the striatal D2R-expressing neurons will be discussed in relation to the basal ganglia circuitry. doi:10.1016/j.neures.2009.09.1097 P3-a28 Effects of high-frequency local stimulation on pallidal neuronal activity Satomi Chiken, Atsushi Nambu Division of System Neurophysiology, National Institute for Physiological Sciences and Sokendai, Okazaki, Japan High-frequency stimulation or deep brain stimulation (DBS) targeting the internal segment of globus pallidus (GPi), an output nucleus of basal ganglia, can ameliorate motor symptoms of dystonia and Parkinson’s disease. To elucidate the mechanisms of DBS, we observed neuronal activity of GPi neurons in response to local GPi stimulation in normal monkeys. Single stimulation evoked a GABAA receptor mediated short inhibition in GPi neurons. High-frequency stimulation inhibited spontaneous firings of the GPi neurons. Moreover, cortically evoked triphasic responses in the GPi were also inhibited during high-frequency stimulation. Directly activated action potentials following stimulus artifact were sometimes observed. These results suggest that GPi-DBS dissociates inputs and outputs of GPi neurons and disrupts information flow through the GPi. doi:10.1016/j.neures.2009.09.1098 P3-a29 Transcranial optogenetic stimulation for mapping of the motor cortex Riichiro Hira1,3, Fuki Okubo1, Naoki Honkura1, Jun Noguchi1, Yoshio Maruyama2, George J. Augustine3, Haruo Kasai1, Masanori Matsuzaki1 1 Dept Structual Physiol, Univ of Tokyo, Japan; 2 Dept of Physiol, Tohoku Univ, Japan; 3 Dept of Neurobiol, Duke Univ, USA We developed a method that uses Channelrhodopsin-2 (ChR2) for transcranial optogenetic stimulation. This method is based on scanning a light beam over the brain, thereby photostimulating ChR2-expressing neurons in intact mice. As a proof of principle, we applied this technique to the motor cortex of transgenic mice expressing ChR2 in cortical pyramidal cells. Photostimulation induced limb movements that were time-locked with millisecond precision and could be induced at frequencies up to 20 Hz. By scanning this light beam, we could map the distribution of neurons associated with limb movement. With this approach we could simultaneously define motor maps controlling two limbs and could reproducibly generate such cortical motor maps over periods of weeks. Moreover we determined spatial resolutions by recording action potentials or LFPs in the motor cortex. doi:10.1016/j.neures.2009.09.1099 P3-a30 Dual modulation of GABAergic inputs to cholinergic interneurons in the striosomes and matrix compartments of the striatum Masami Miura, Masao Masuda, Toshihiko Aosaki Tokyo Metropolitan Institute of Gerontology, Japan Striatal cholinergic interneurons play an important role in regulating several aspects of behavioral functions. Interestingly, cholinergic interneurons are preferentially distributed on the border of striosomes and matrix compartments. In this study, we investigated the GABAergic input to cholinergic interneurons and found that intrastriatal stimulation evoked multiphasic GABAergic IPSCs which were dually modulated by -opioid receptors (MORs) and nicotinic receptors (nAchRs). DAMGO (1 M), an agonist of MOR, suppressed the early component of IPSCs only in the striosomes. In contrast, dihydro-erythroidine (DH E, 1 M), an antagonist of non7 nAchR, suppressed the late component of IPSCs throughout the striatum. These results indicate that inhibition of nAchR and activation of MOR may affect the excitability of cholinergic interneurons, and thus modulate the activity of the striosome/matrix compartments/matrix compartments. doi:10.1016/j.neures.2009.09.1100 P3-a31 Effects of the vestibular nucleus stimulation on the masseteric monosynaptic reflex Yoshihide Satoh, Ken’Ichi Ishizuka, Toshiki Murakami Nippon Dental University, Japan The effects of the vestibular nucleus (VN) stimulation on the masseteric monosynaptic reflex (MMR) were studied in anesthetized rats. The MMR was evoked by electrical stimulation of the mesencephalic trigeminal nucleus and was recorded as electromyographic responses of the masseter muscle bilaterally. The effects of the conditioning VN stimulation were expressed as the change in MMR amplitude as a percentage of the control. Conditioning electrical stimulation of the parvicellular and the magnocellular part of the medial VN significantly facilitated the MMR bilaterally. Facilitation commenced at a conditioning-test interval of 2 ms, and reached a maximum of the control level at 8–10 ms. In contrast, conditioning electrical stimulation of the inferior VN inhibited the MMR bilaterally. Inhibition reached a maximum of the control level at 6.0 ms. These results suggest that the VN is involved in modulation of the MMR. doi:10.1016/j.neures.2009.09.1101 P3-a32 Post-spike effects of spinal interneuron in monkeys performing a precision grip task Tomohiko Takei1, Kazuhiko Seki1,2 1 Dept Dev Physiol, NIPS, Okazaki, Japan; 2 Sch Life Sci, Grad Univ Adv Stud,