Biomedical subjects

Satomi Chiken

Publications and source records attributed to Satomi Chiken.

10 recordsLinked to original sources

PubMed2007

Serotonin modulates pallidal neuronal activity in the awake monkey.

Serotonin (5-HT)-containing neurons in the dorsal raphe project to the external and internal segments of the pallidum, which express several 5-HT receptors. Although the involvement of 5-HT in basal ganglia movement control has been suggested, little is known about the physiological action of 5-HT in the pallidum. Previous anatomical studies and in vitro physiological studies in other brain areas have suggested the following possibilities: (1) 5-HT suppresses GABAergic inhibition through presynaptic 5-HT1B receptors; (2) 5-HT decreases the firing of pallidal neurons through postsynaptic 5-HT1A receptors; and (3) 5-HT postsynaptically excites pallidal neurons through activation of 5-HT2C, 5-HT4, or 5-HT7 receptors. To test these possibilities, we examined the effects of locally applied agonists and antagonists of 5-HT on spontaneous neuronal firing and on excitatory and inhibitory responses of pallidal neurons to electrical stimulation of the motor cortex in awake monkeys. Although in vivo experiments could not conclusively determine the receptor types or the active sites involved in the observed effects, the results suggested the following possibilities: (1) 5-HT strongly suppresses GABAergic inhibition probably through 5-HT1B receptors; (2) in the external pallidal segment, the suppression may involve additional receptors or mechanisms; and (3) 5-HT suppresses glutamatergic excitation probably through 5-HT1A (and not 5-HT1B) receptors. The present study did not isolate or identify the existence of strong, direct postsynaptic inhibitory or excitatory effects of 5-HT. Thus, present results imply that 5-HT modulates synaptic inputs of both pallidal segments and exerts a significant role in movement control.

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PubMed2006

Origins of GABA(A) and GABA(B) receptor-mediated responses of globus pallidus induced after stimulation of the putamen in the monkey.

The external and internal segments of the pallidum (GPe and GPi) receive heavy GABAergic innervations from the neostriatum, an input nucleus of the basal ganglia. The GPe neurons provide another major GABAergic innervation to the GPe itself and GPi. Although these GABAergic inputs are considered to play key roles in controlling the level and pattern of firing activity of pallidal neurons in both normal and pathophysiological conditions, these inputs have not been well characterized in vivo. Here, we characterized the responses of pallidal neurons to single and burst stimulation of the putamen (Put) in awake monkeys. Unit recordings in combination with local infusion of drugs and a chemical blockade of the subthalamic nucleus (STN), the major origin of excitatory afferents, revealed the following. Under STN blockade, the duration of single Put stimulation induced gabazine (a GABA(A) antagonist)-sensitive responses differed greatly in the GPe ( approximately 400 ms long) and in the GPi (60 ms long). Burst stimulation of the Put induced CGP55845 [(2S)-3-[[(1S)-1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl)phosphinic acid] (a GABA(B) antagonist)-sensitive responses in the GPe and GPi. However, the data suggested that the origin of the GABA(B) responses was the GPe, not the Put. Local CGP55845 application increased the spontaneous firing of GPe and GPi neurons, suggesting that GABA released from the axons of GPe neurons effectively activates GABA(B) receptors in the GPe and GPi and contributes significantly to the control of the level of neuronal activity.

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PubMed2005

Balance of monosynaptic excitatory and disynaptic inhibitory responses of the globus pallidus induced after stimulation of the subthalamic nucleus in the monkey.

The subthalamic nucleus (STN) plays a pivotal role in controlling the activity of both the external and internal segments of the globus pallidus (GPe and GPi, respectively). Both nuclei receive monosynaptic excitatory and disynaptic GPe-mediated inhibitory inputs from the STN. Thus, we investigated the balance of these antagonistic inputs that may determine the overall response of pallidum to STN activation in monkeys. Single stimulation of the STN evoked a short-latency excitation followed by a weak inhibition in GPe neurons and a short-latency, very short-duration excitation followed by a strong inhibition in GPi neurons. Burst high-frequency stimulation (BHFS) (10 stimuli with 100 Hz) of the STN (STN-BHFS) evoked powerful excitatory responses in GPe neurons. Local injection of a mixture of 1, 2, 3, 4-tetrahydro-6-nitro-2, 3-dioxobenzo[f]quinoxaline-7-sulfonamide (NBQX; AMPA/kainate receptor blocker) and 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP; NMDA receptor blocker) greatly diminished or abolished excitatory responses to the STN stimulation. In contrast to the GPe, STN-BHFS evoked a predominantly inhibitory response in GPi neurons. The inhibition could be blocked either by a local application of the GABAA receptor antagonist gabazine or by an injection of an NBQX/CPP/gabazine mixture into the GPe. STN-BHFS induced weak excitatory or inhibitory responses in a small number of phasically active putamen neurons. These data suggest that with single stimulation and during STN-BHFS, the STN-GPe excitatory response dominates over the STN-GPe-GPe recurrent inhibition in the GPe, whereas the STN-GPe-GPi inhibitory response dominates over the STN-GPi excitatory response in the GPi.

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PubMed2005

Impairment of skilled forelimb use after ablation of striatal interneurons expressing substance P receptors in rats: an analysis using a pasta matrix reaching task.

Local injection of substance P (SP)-saporin can cause selective ablation of striatal interneurons expressing SP receptors (SPR). In this study, we evaluated quantitatively the impairment of skilled forelimb use after unilateral ablation of the striatal interneurons using a pasta matrix reaching task in rats. We found a significant decrease of the number of the pasta pieces (uncooked spaghetti) retrieved using the paw of the experimental side contralateral to the ablation, whereas the number of the pasta pieces retrieved using the paw of the intact side increased significantly. These findings, with our previous reports, suggest that the modulation of the cortico-striato-entopeduncular direct pathway by striatal interneurons is important for maintaining normal basal-ganglia control for skilled forelimb movements.

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PubMed2004

Three-dimensional ultrasonography of monkey brain.

Three-dimensional (3D) ultrasonography is new technology based on automatic volume acquisition of ultrasound images, and computer-aided image reconstruction. In the present study, we used a commercially available 3D ultrasonographic instrument for electrophysiological and neuroanatomical experiments in the macaque monkey. 3D reconstruction for multiplanar analysis and surface rendering were useful to observe the microelectrode or microinjection pipette in the cerebral cortex or deep brain structure. The present results indicate that the 3D ultrasonography for monkey brain is a more powerful tool for experiments in vivo than conventional two-dimensional (2D) ultrasonography.

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PubMed2003

Cytochrome oxidase activity in the monkey globus pallidus and subthalamic nucleus after ablation of striatal interneurons expressing substance P receptors.

To understand functional roles of striatal interneurons in primate basal ganglia circuitry, we ablated interneurons expressing substance P (SP) receptors (SPR) in the putamen with SP-saporin, a SPR selective neurotoxin. The effect of SP-saporin injection into the putamen was evaluated by examining the loss of cholinergic interneurons and NADPHd-positive (nicotinamide adenine dinucleotide phosphate diaphorase positive) interneurons. We then analyzed regional metabolic changes using cytochrome oxidase (CO) histochemistry. CO activity in some regions of the internal and external segments of the globus pallidus (GP) in the lesioned hemisphere was lower than that in the contralateral or surrounding GP regions. CO activity in the subthalamic nucleus, however, showed no significant change. The present findings suggest that striatopallidal projection neurons exert enhanced inhibitory influence on the GP without modulatory control by the striatal SPR-expressing interneurons.

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PubMed2003

Fluorescence digital photomacrography.

Low-power photographs of brain sections have been needed for neuroanatomical studies. This paper describes a setup for fluorescence digital photomacrography. High-resolution digital images were obtained with commercially available digital cameras combined with an oblique fluorescence illumination and filters for excitation and emission. The image of an entire coronal section of the macaque brain could be taken with a single exposure. The present photographic system would be useful not only for neuroanatomical, but also for histological, embryological or pathological studies that require low-magnification fluorescence images.

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PubMed2003

Ablation of striatal interneurons influences activities of entopeduncular neurons.

To characterize modulatory effects of striatal interneurons upon the output nucleus of the basal ganglia, we ablated striatal interneurons that express substance P receptors by using local injection of a selective neurotoxin, substance P-saporin, in rats. We then made extracellular recordings of the activity of entopeduncular neurons and examined their responses to stimulation in the motor cortex. In the interneuron-ablated animals, the spontaneous discharge rate of entopeduncular neurons was significantly decreased, and the proportion of entopeduncular neurons showing responses to cortical stimulation was significantly larger, in comparison with intact animals. It is suggested that striatal interneurons expressing substance P receptors are important for motor control mechanisms mediated by the cortico-basal ganglia pathways.

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PubMed2002

Efferent projections from the striatal patch compartment: anterograde degeneration after selective ablation of neurons expressing mu-opioid receptor in rats.

Local injection of mu-opioid receptor specific neurotoxin, dermorphin-saporin, into the striatum resulted in selective degeneration of striatal neurons in the patch compartment. We analyzed subsequent anterograde degeneration of axons and terminals at light and electron microscopic level. Light microscopic examination after silver impregnation method revealed that degenerating axons and terminals arising from the striatal patch compartment were distributed in the globus pallidus, entopeduncular nucleus, and substantia nigra. They were found in both pars reticulata and compacta of the substantia nigra. Electron microscopic examination revealed that the degenerating axon terminals contained large pleomorphic vesicles and formed symmetric synapses on dendrites. The present results suggest that patch neurons expressing mu-opioid receptor send projection fibers to multiple nuclei of the basal ganglia.

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PubMed2002

An improved method with a long-shanked glass micropipette and ultrasonography for drug injection into deep brain structure of the monkey.

We describe an improved method to inject drug into deep brain structure of the macaque monkey. A Teflon-coated tungsten wire for extracellular recording was passed through a long-shanked (4-5 cm) glass micropipette, which was then attached to a microsyringe with dental impression material. The surface of the micropippete was coated with Teflon to reduce acoustic artifact in ultrasound imaging. Thereby, it was possible to identify the micropipette in the brain with B-mode ultrasonography. Extracellular recording combined with electrical stimulation in the input source of the target nucleus was also helpful to determine the location of the micropipette. Here, we demonstrate injection of a neuronal tracer, wheat germ agglutinin conjugated to horseradish peroxidase, into the medial mammillary nucleus of the Japanese monkey.

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