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Thibos LN, Bradley A, Xu R, Lopez-Gil N. Ricco's law and absolute threshold for foveal detection of black holes. J Opt Soc Am A Opt Image Sci Vis 2019; 36:B35-B43. [PMID: 31044953 DOI: 10.1364/josaa.36.000b35] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/22/2019] [Indexed: 06/09/2023]
Abstract
Visual detection of small black objects surrounded by a light background depends on background luminance, pupil size, optical blur, and object size. Holding pupil and optics fixed, we measured the minimum background luminance needed for foveal detection of small black targets as a function of target size. For all three observers, absolute threshold varied inversely with target area when disk diameter subtended less than 10' of visual angle. For target diameter ≥10', threshold remained constant at about 0.3 Td, which was also the absolute threshold for detecting light spots 10' or larger in diameter on a black background. These results are consistent with Ricco's law of spatial summation: a "black hole" is just detectable when the background luminance is sufficiently high for its absence inside the Ricco area to reduce 555 nm photon flux by 7500 photons/s, which is the same change needed to detect light spots on a black surround. These results can be accounted for by a differential pair of Ricco detectors, each about the size of the receptive field center of magocellular retinal ganglion cells when projected into object space through the eye's weakly aberrated optical system. Statistical analysis of the model suggests the quantum fluctuations due to internal, biological noise (i.e., "scotons") are a greater handicap than the photon fluctuations inherent in the light stimulus at absolute foveal threshold.
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Reeves A, Grayhem R. Role of extrinsic noise in the sensitivity of the rod pathway: rapid dark adaptation of nocturnal vision in humans. J Opt Soc Am A Opt Image Sci Vis 2016; 33:351-360. [PMID: 26974904 DOI: 10.1364/josaa.33.000351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
UNLABELLED Rod-mediated 500 nm test spots were flashed in Maxwellian view at 5 deg eccentricity, both on steady 10.4 deg fields of intensities (I) from 0.00001 to 1.0 scotopic troland (sc td) and from 0.2 s to 1 s after extinguishing the field. On dim fields, thresholds of tiny (5') tests were proportional to √I (Rose-DeVries law), while thresholds after extinction fell within 0.6 s to the fully dark-adapted absolute threshold. Thresholds of large (1.3 deg) tests were proportional to I (Weber law) and extinction thresholds, to √I. CONCLUSIONS rod thresholds are elevated by photon-driven noise from dim fields that disappears at field extinction; large spot thresholds are additionally elevated by neural light adaptation proportional to √I. At night, recovery from dimly lit fields is fast, not slow.
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Patterson EJ, Bargary G, Barbur JL. Understanding disability glare: light scatter and retinal illuminance as predictors of sensitivity to contrast. J Opt Soc Am A Opt Image Sci Vis 2015; 32:576-85. [PMID: 26366766 DOI: 10.1364/josaa.32.000576] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The presence of a bright light in the visual field has two main effects on the retinal image: reduced contrast and increased retinal illuminance because of scattered light; the latter can, under some conditions, lead to an improvement in retinal sensitivity. The combined effect remains poorly understood, particularly at low light levels. A psychophysical flicker-cancellation test was used to measure the amount and angular distribution of scattered light in the eye for 40 observers. Contrast thresholds were measured using a functional contrast sensitivity test. Pupil-plane glare-source illuminances (i.e., 0, 1.35, and 19.21 lm/m2), eccentricities (5°, 10°, and 15°), and background luminances (1, 2.6, and 26 cd/m2) were investigated. Visual performance was better than predicted, based on a loss of retinal image contrast caused by scattered light, particularly in the mesopic range. Prediction accuracy improved significantly when the expected increase in retinal sensitivity in the presence of scattered light was also incorporated in the model.
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Krause P, Foerderreuther S, Straube A. Effects of conditioning peripheral repetitive magnetic stimulation in patients with complex regional pain syndrome. Neurol Res 2013; 27:412-7. [PMID: 15949240 DOI: 10.1179/016164105x17224] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES We tested whether repetitive magnetic stimulation (rMS) induces an afferent input to the spinocerebral tract in patients with complex regional pain syndrome (CRPS). METHODS Cortical and spinal motor evoked potentials (cMEP and sMEP), as well as the contra- and ipsilateral silent period (cCSP and iCSP), were recorded in patients with CRPS type I before and after conditioning rMS, applied at cervical nerve roots innervating affected muscles. Patients were compared with a group of healthy subjects. RESULTS In the group of patients we found that cMEP amplitudes were always significantly smaller for both hemispheres. In the group of healthy subjects we found a significant prolongation of the cCSP and iCSP after rMS. This was absent in patients. SMEP were always unchanged in both groups. DISCUSSION This led us to the explanation that the afferent input to the motor cortical system in CRPS patients is less effective than in healthy subjects.
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Affiliation(s)
- Phillip Krause
- Department of Neurology, University of Munich, Klinikum Grosshadern, Munich, Germany.
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Weng S, Estevez ME, Berson DM. Mouse ganglion-cell photoreceptors are driven by the most sensitive rod pathway and by both types of cones. PLoS One 2013; 8:e66480. [PMID: 23762490 PMCID: PMC3676382 DOI: 10.1371/journal.pone.0066480] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/07/2013] [Indexed: 11/21/2022] Open
Abstract
Intrinsically photosensitive retinal ganglion cells (iprgcs) are depolarized by light by two mechanisms: directly, through activation of their photopigment melanopsin; and indirectly through synaptic circuits driven by rods and cones. To learn more about the rod and cone circuits driving ipRGCs, we made multielectrode array (MEA) and patch-clamp recordings in wildtype and genetically modified mice. Rod-driven ON inputs to ipRGCs proved to be as sensitive as any reaching the conventional ganglion cells. These signals presumably pass in part through the primary rod pathway, involving rod bipolar cells and AII amacrine cells coupled to ON cone bipolar cells through gap junctions. Consistent with this interpretation, the sensitive rod ON input to ipRGCs was eliminated by pharmacological or genetic disruption of gap junctions, as previously reported for conventional ganglion cells. A presumptive cone input was also detectable as a brisk, synaptically mediated ON response that persisted after disruption of rod ON pathways. This was roughly three log units less sensitive than the rod input. Spectral analysis revealed that both types of cones, the M- and S-cones, contribute to this response and that both cone types drive ON responses. This contrasts with the blue-OFF, yellow-ON chromatic opponency reported in primate ipRGCs. The cone-mediated response was surprisingly persistent during steady illumination, echoing the tonic nature of both the rod input to ipRGCs and their intrinsic, melanopsin-based phototransduction. These synaptic inputs greatly expand the dynamic range and spectral bandpass of the non-image-forming visual functions for which ipRGCs provide the principal retinal input.
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Affiliation(s)
- Shijun Weng
- Department of Neuroscience, Brown University, Providence, Rhode Island, United States of America
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, P.R. China
| | - Maureen E. Estevez
- Department of Neuroscience, Brown University, Providence, Rhode Island, United States of America
| | - David M. Berson
- Department of Neuroscience, Brown University, Providence, Rhode Island, United States of America
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Dickey TC, Tych R, Kliot M, Loeser JD, Pederson K, Mourad PD. Intense focused ultrasound can reliably induce sensations in human test subjects in a manner correlated with the density of their mechanoreceptors. Ultrasound Med Biol 2012; 38:85-90. [PMID: 22104527 PMCID: PMC3245865 DOI: 10.1016/j.ultrasmedbio.2011.09.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 09/21/2011] [Accepted: 09/29/2011] [Indexed: 05/09/2023]
Abstract
Sensations generated by intense focused ultrasound (iFU) can occur cutaneously and/or at depth, in contrast to other forms of stimulation (e.g., heat, electricity), whose action usually occurs only at the skin surface, or mechanical stimulation (e.g., von Frey hairs, calibrated forceps, tourniquets) that compress and thus stimulate all tissue. Previous work on iFU stimulation has led to the hypothesis that the tactile basis of iFU stimulation should correlate with the density of mechanoreceptors at the site of iFU stimulation. Here we tested that hypothesis, correlating a "two-point" neurological examination-a standard measure of superficial mechanoreceptor density-with the intensity of superficially applied iFU necessary to generate sensations with high sensitivity and specificity. We applied iFU at 1.1 MHz for 0.1 s to the fingertip pads of 17 test subjects in a blinded fashion and escalated intensities until they consistently observed iFU-induced sensations. Most test subjects achieved high values of sensitivity and specificity, doing so at values of spatially and temporally averaged intensity measuring <100 W/cm(2). Moreover, the test subjects' sensitivity to iFU stimulation correlated with the density of mechanoreceptors as determined by a standard two-point discrimination neurological examination, consistent with earlier hypotheses.
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Affiliation(s)
| | | | | | - John D. Loeser
- Department of Neurological Surgery UW
- Department of Anesthesiology and Pain Medicine UW
| | | | - Pierre D. Mourad
- Department of Neurological Surgery UW
- Applied Physics Laboratory UW
- Department of Bioengineering UW
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Geber C, Baumgärtner U, Fechir M, Vogt T, Birklein F, Treede RD. Comparison of LEP and QST and their contribution to standard sensory diagnostic assessment of spinal lesions: a pilot study. Neurol Sci 2011; 32:401-10. [PMID: 21293898 DOI: 10.1007/s10072-011-0476-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Accepted: 01/04/2011] [Indexed: 10/18/2022]
Abstract
This study evaluates the additional use of laser-evoked potentials (LEP) and quantitative sensory testing (QST) in the sensory assessment of spinal lesions. Four consecutive patients with spinal lesions verified by MRI and clinical evidence for mild spinothalamic tract involvement were included. The electrophysiological workup [somatosensory evoked potentials (SEP) and LEP] was compared to QST. Electrophysiology and QST were reassessed after about 6 months. LEP detected impaired spinothalamic tract function in 7/8 examinations. QST pointed to spinothalamic tract lesions by loss of thermal function (3/8); most frequent positive sensory signs (3/8) were paradoxical heat sensations. LEP and QST results were concordant in 6/8 examinations. SEPs were abnormal in 2/8 examinations. Congruent results between SEP and both LEP and QST were obtained in 3/8 examinations. LEP detected more deficits than any single QST parameter or their combination but additional QST allows the detection of positive sensory signs. The diagnostic gain of SEP was limited.
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Affiliation(s)
- Christian Geber
- Klinik und Poliklinik für Neurologie, Universitätsmedizin der Johannes-Gutenberg Universität, Langenbeckstrasse 1, 55131 Mainz, Germany.
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Affiliation(s)
- M Yamazaki
- Pathology Division, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan
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Duke AR, Cayce JM, Malphrus JD, Konrad P, Mahadevan-Jansen A, Jansen ED. Combined optical and electrical stimulation of neural tissue in vivo. J Biomed Opt 2009; 14:060501. [PMID: 20059232 PMCID: PMC2789115 DOI: 10.1117/1.3257230] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 08/13/2009] [Accepted: 09/08/2009] [Indexed: 05/25/2023]
Abstract
Low-intensity, pulsed infrared light provides a novel nerve stimulation modality that avoids the limitations of traditional electrical methods such as necessity of contact, presence of a stimulation artifact, and relatively poor spatial precision. Infrared neural stimulation (INS) is, however, limited by a 2:1 ratio of threshold radiant exposures for damage to that for stimulation. We have shown that this ratio is increased to nearly 6:1 by combining the infrared pulse with a subthreshold electrical stimulus. Our results indicate a nonlinear relationship between the subthreshold depolarizing electrical stimulus and additional optical energy required to reach stimulation threshold. The change in optical threshold decreases linearly as the delay between the electrical and optical pulses is increased. We have shown that the high spatial precision of INS is maintained for this combined stimulation modality. Results of this study will facilitate the development of applications for infrared neural stimulation, as well as target the efforts to uncover the mechanism by which infrared light activates neural tissue.
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Abstract
Although the 50 Hz electric current perception threshold is a key parameter for limiting electric touch currents in electrical technology and for limiting indirect effects of external electromagnetic fields, the data available mainly reflect men's perception ability; with only sparse data for women and almost none for children or the elderly. Measurements with 240 children aged 9 - 16 years, and 123 elderly people, allow this gap of knowledge to be filled. Taking into account the demographic age distribution, it was possible to generate a probability distribution representing the perception ability of the overall general population, and thus to provide a more established basis for deriving safety limits. The results show that the existing limit values for electric touch currents are considerably too high if compared with results derived from the new data with the same criteria. On the other hand, it appeared that children do not exhibit such a high sensitivity to electricity as assumed to date. Therefore, former rule-of-thumb estimates to account for higher sensitivities of children lie on the safe side. The presented assessment of the general population's electric current perception ability should stimulate a critical review of the existing regulations.
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Affiliation(s)
- N Leitgeb
- Institute of Clinical Engineering, Graz University of Technology, Inffeldgasse 16a, Graz, Austria.
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Abstract
It has been suggested that in lower vertebrates, visual signals are propagated in the retina using mixed bipolar cell pathways. In this article, we examined rod and cone signaling transmission in the retina of teleost zebrafish. Full-field electroretinograms (ERGs) were recorded from the cornea of control or 2-amino-4-phosphonobutyric acid (APB)-treated zebrafish. During dark adaptation following bright light adaptation, the intensity-response (V-log I) curve for both the ERG b- and d-waves shifted. In control animals, the b-wave response displayed a typical visual Purkinje shift and became more sensitive. By contrast, the d-wave became less sensitive. In the early dark adaptation, cone-dominant signals were readily recorded in both b- and d-waves. In the late dark adaptation, rod signals became dominant. However, no obvious d-wave was recorded. Intraocular injections of APB selectively blocked the b-wave, but revealed the d-wave in both early and late dark adaptation.
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Affiliation(s)
- Jason Q Ren
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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Lörincz ML, Crunelli V, Hughes SW. Cellular dynamics of cholinergically induced alpha (8-13 Hz) rhythms in sensory thalamic nuclei in vitro. J Neurosci 2008; 28:660-71. [PMID: 18199766 PMCID: PMC2778076 DOI: 10.1523/jneurosci.4468-07.2008] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 11/16/2007] [Accepted: 11/21/2007] [Indexed: 11/21/2022] Open
Abstract
Although EEG alpha (8-13 Hz) rhythms are traditionally thought to reflect an "idling" brain state, they are also linked to several important aspects of cognition, perception, and memory. Here we show that reactivating cholinergic input, a key component in normal cognition and memory operations, in slices of the cat primary visual and somatosensory thalamus, produces robust alpha rhythms. These rhythms rely on activation of muscarinic receptors and are primarily coordinated by activity in the recently discovered, gap junction-coupled subnetwork of high-threshold (HT) bursting thalamocortical neurons. By performing extracellular field recordings in combination with intracellular recordings of these cells, we show that (1) the coupling of HT bursting cells is sparse, with individual neurons typically receiving discernable network input from one or very few additional cells, (2) the phase of oscillatory activity at which these cells prefer to fire is readily modifiable and determined by a combination of network input, intrinsic properties and membrane polarization, and (3) single HT bursting neurons can potently influence the local network state. These results substantially extend the known effects of cholinergic activation on the thalamus and, in combination with previous studies, show that sensory thalamic nuclei possess powerful and dynamically reconfigurable mechanisms for generating synchronized alpha activity that can be engaged by both descending and ascending arousal systems.
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Affiliation(s)
- Magor L. Lörincz
- School of Biosciences, Cardiff University, Cardiff CF10 3US, United Kingdom
| | - Vincenzo Crunelli
- School of Biosciences, Cardiff University, Cardiff CF10 3US, United Kingdom
| | - Stuart W. Hughes
- School of Biosciences, Cardiff University, Cardiff CF10 3US, United Kingdom
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Maurer K, Bostock H, Koltzenburg M. A rat in vitro model for the measurement of multiple excitability properties of cutaneous axons. Clin Neurophysiol 2007; 118:2404-12. [PMID: 17897875 DOI: 10.1016/j.clinph.2007.08.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 08/14/2007] [Accepted: 08/18/2007] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To establish an in vitro model for measurement of the excitability properties of cutaneous sensory axons. METHODS We used a saphenous skin-nerve preparation from adult rat in combination with computerized threshold tracking. We measured strength-duration time constant, the recovery of excitability after a supramaximal stimulus and the accommodation to conditioning subthreshold polarizing stimuli (threshold electrotonus, current-threshold relationship) and compared these with previously published recordings from sensory axons in human median nerve. RESULTS Threshold electrotonus and the amplitude of superexcitability were indistinguishable between human median nerve in vivo and rat saphenous nerve in vitro, but several excitability parameters were significantly different in the rat: strength-duration time constant was significantly shorter (0.19+/-0.01 vs. 0.53+/-0.02 ms); the refractory period was shorter (1.9+/-1.1 ms vs. 3.5+/-1.0 ms) and late subexcitability was smaller (6.3+/-0.3% vs. 11.3+/-0.5%); thirdly, during recording of current-threshold relationship, rat nerves displayed more inward rectification to strong hyperpolarizing currents. Parameters were stable over more than 3h. CONCLUSIONS Excitability changes of sensory Abeta-fibres can be reliably studied in the rat in vitro and are qualitatively similar to humans. SIGNIFICANCE This rat model will facilitate pharmacological studies of nerve excitability and work on models of neuropathy.
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Affiliation(s)
- Konrad Maurer
- UCL Institute of Child Health, UCL, 30 Guilford St., London WC1N 1 EH, United Kingdom
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Sale MV, Ridding MC, Nordstrom MA. Factors influencing the magnitude and reproducibility of corticomotor excitability changes induced by paired associative stimulation. Exp Brain Res 2007; 181:615-26. [PMID: 17487476 DOI: 10.1007/s00221-007-0960-x] [Citation(s) in RCA: 214] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 04/10/2007] [Indexed: 11/25/2022]
Abstract
Several paired-associative stimulation (PAS) protocols induce neuroplastic changes in human motor cortex (M1). To understand better the inherent variability of responses to PAS, we investigated the effectiveness and reproducibility of two PAS paradigms, and neurophysiological and experimental variables that may influence this. Motor evoked potentials (MEPs) were elicited by transcranial magnetic stimulation (TMS) of right M1, and recorded from surface EMG of left abductor pollicis brevis (APB) and first dorsal interosseous before and after PAS. PAS consisted of electrical stimulation of left median nerve paired with TMS over right M1 25 ms later. Twenty subjects were given one of two PAS protocols: short (132 paired stimuli at 0.2 Hz) or long (90 paired stimuli at 0.05 Hz), and were re-tested with the same protocol on 3 separate occasions, with 11 subjects tested in the morning and 9 in the afternoon. Neurophysiological variables assessed included MEP amplitude, resting and active motor threshold, short-interval intracortical inhibition, intracortical facilitation and cortical silent period duration. The short PAS protocol produced greater APB MEP facilitation (51%) than the long protocol (11%), and this did not differ between sessions. The neurophysiological variables did not consistently predict responses to PAS. Both PAS protocols induced more APB MEP facilitation, and greater reproducibility between sessions, in experiments conducted in the afternoon. The mechanism for this is unclear, but circadian rhythms in hormones and neuromodulators known to influence neuroplasticity warrant investigation. Future studies involving PAS should be conducted at a fixed time of day, preferably in the afternoon, to maximise neuroplasticity and reduce variability.
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Affiliation(s)
- Martin V Sale
- Discipline of Physiology and Research Centre for Human Movement Control, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, SA 5005, Australia.
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Imada M, Misawa S, Sawai S, Tamura N, Kanai K, Sakurai K, Sakamoto S, Nomura F, Hattori T, Kuwabara S. Median-radial sensory nerve comparative studies in the detection of median neuropathy at the wrist in diabetic patients. Clin Neurophysiol 2007; 118:1405-9. [PMID: 17452013 DOI: 10.1016/j.clinph.2007.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 02/18/2007] [Accepted: 03/08/2007] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Median-ulnar comparative studies (MUCS) play an important role in the electrodiagnosis of carpal tunnel syndrome, but in diabetes concomitant involvement of Guyon's canal (ulnar nerve compression at the wrist) would reduce the sensitivity of MUCS. This study tested the utility of median-radial comparative studies (MRCS) in diabetic patients. METHODS Anti-dromic MUCS and MRCS were prospectively performed in 120 patients with diabetes, and 64 normal controls. In 28 diabetic patients, latent addition using threshold tracking was performed in superficial radial sensory axons to estimate persistent nodal sodium currents. RESULTS MUCS was abnormal in 49% of the diabetic patients, and MRCS was abnormal in 58%. Median motor distal latencies were prolonged in 38%, and median sensory nerve conduction velocities were slowed in 40%. The longer latency differences in MRCS were associated with smaller persistent sodium currents, suggesting that intra-axonal sodium accumulation mediated by hyperglycemia enhances nerve compression. CONCLUSIONS MRCS appears to be the most sensitive electrodiagnostic test in the detection of median neuropathy at the wrist in diabetic patients. Nerve conduction slowing across the carpal tunnel may be associated with metabolic abnormalities under hyperglycemia. SIGNIFICANCE Assessment of nerve conduction across the common entrapment sites could provide new insights into the pathophysiology of diabetic neuropathy related to metabolic factors.
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Affiliation(s)
- Megumi Imada
- Department of Clinical Laboratory, Graduate School of Medicine, Chiba University, 1-8-1 Inohama, Chiba, Japan
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Dong XD, Mann MK, Kumar U, Svensson P, Arendt-Nielsen L, Hu JW, Sessle BJ, Cairns BE. Sex-related differences in NMDA-evoked rat masseter muscle afferent discharge result from estrogen-mediated modulation of peripheral NMDA receptor activity. Neuroscience 2007; 146:822-32. [PMID: 17382479 PMCID: PMC1976542 DOI: 10.1016/j.neuroscience.2007.01.051] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Revised: 01/25/2007] [Accepted: 01/30/2007] [Indexed: 10/23/2022]
Abstract
In the present study, the hypothesis that sex-related differences in glutamate-evoked rat masseter muscle afferent discharge may result from estrogen-related modulation of peripheral N-methyl-d-aspartate (NMDA) receptor activity and/or expression was tested by examining afferent fiber discharge in response to masseter injection of NMDA and the expression of NR2A/B subunits by masseter ganglion neurons in male and female rats. The results showed that injection of NMDA into the masseter muscle evoked discharges in putative mechanonociceptive afferent fibers and increased blood pressure that was concentration-dependent, however, a systemic action of NMDA appeared responsible for increased blood pressure. NMDA-evoked afferent discharge was significantly greater in female than in male rats, was positively correlated with plasma estrogen levels in females and was significantly greater in ovariectomized female rats treated with a high dose (5 mug/day) compared with a low dose (0.5 mug/day) of estrogen. Pre-treatment of high dose estrogen-treated-ovariectomized female rats with the Src tyrosine kinase inhibitor PP2 did not affect NMDA-evoked afferent discharge. NMDA-evoked afferent discharge was attenuated by the antagonists ketamine and ifenprodil, which is selective for NR2B containing NMDA receptors. Fewer masseter ganglion neurons expressed the NR2A (16%) subunit as compared with the NR2B subunit (38%), which was expressed at higher frequencies in intact female (46%) and high dose estrogen-treated ovariectomized female (60%) rats than in male (31%) rats. Taken together, these results suggest that sex-related differences in NMDA-evoked masseter afferent discharge are due, at least in part, to an estrogen-mediated increase in expression of peripheral NMDA receptors by masseter ganglion neurons in female rats.
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Affiliation(s)
- Xu-Dong Dong
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Mandeep K. Mann
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Peter Svensson
- Department of Clinical Oral Physiology, Dental School, Århus University, DK-8000 Århus C, Denmark
| | - Lars Arendt-Nielsen
- Laboratory for Experimental Pain Research, Center for Sensory-Motor Interaction, Aalborg University, DK-9220, Denmark
| | - James W. Hu
- Faculty of Dentistry, The University of Toronto, Toronto, Ontario, M5G 1G6 Canada
| | - Barry J. Sessle
- Faculty of Dentistry, The University of Toronto, Toronto, Ontario, M5G 1G6 Canada
| | - Brian E. Cairns
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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Ohara S, Taghva A, Kim JH, Lenz FA. Spontaneous low threshold spike bursting in awake humans is different in different lateral thalamic nuclei. Exp Brain Res 2007; 180:281-8. [PMID: 17256161 DOI: 10.1007/s00221-007-0856-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 01/03/2007] [Indexed: 10/23/2022]
Abstract
Spontaneous action potential bursts associated with low threshold calcium spikes (LTS) occur in multiple human lateral thalamic nuclei, each with different physiologic characteristics. We now test the hypothesis that different patterns of spontaneous LTS bursting occur in these nuclei during awake surgery in patients with essential tremor and the arm at rest. This protocol was chosen to minimize the effect of the patient's disease upon thalamic activity which is a potential confound in a surgical study of this type. Neuronal activity was studied in the human thalamic nuclei receiving somatic sensory input (Vc, ventral caudal), input from the deep cerebellar nuclei (Vim, ventral intermediate), or input from the pallidum (Vo, ventral oral). In each nucleus the burst rates were significantly greater than zero. Burst rates were higher in Vc than in Vim, while firing rates were lower. These findings suggest that neurons in Vc are hyperpolarized and have more frequent inhibitory events. Pre-burst inter-spike intervals (ISIs) were significantly longer in Vc, but were significantly shorter when corrected for the average ISIs between bursts (burst rate/inverse of the primary event rate). These results suggest that inhibitory events in Vc are of lower magnitude relative to a hyperpolarized resting membrane potential. Studies in many species demonstrate that input from the pallidum to the thalamus is inhibitory, suggesting that input to Vo is predominantly inhibitory. However, neurons in Vo have neither slower firing rates nor more frequent LTS bursts. Previous studies have found that spontaneous LTS is similar between classes of neurons within Vc, as defined by their response to thermal and painful stimuli. The differences in spontaneous LTS between human nuclei but not between functional classes within a nucleus may be a basic organizing principle of thalamic inhibitory circuitry.
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Affiliation(s)
- S Ohara
- Department of Neurosurgery, Meyer Building 7-113, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-7713, USA
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18
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Irlenbusch L, Bartsch B, Cooper J, Herget I, Marx B, Raczek J, Thoss F. Influence of a 902.4 MHz GSM signal on the human visual system: Investigation of the discrimination threshold. Bioelectromagnetics 2007; 28:648-54. [PMID: 17654531 DOI: 10.1002/bem.20344] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The proximity of a mobile phone to the human eye raises the question as to whether radiofrequency (RF) electromagnetic fields (EMF) affect the visual system. A basic characteristic of the human eye is its light sensitivity, making the visual discrimination threshold (VDThr) a suitable parameter for the investigation of potential effects of RF exposure on the eye. The VDThr was measured for 33 subjects under standardized conditions. Each subject took part in two experiments (RF-exposure and sham-exposure experiment) on different days. In each experiment, the VDThr was measured continuously in time intervals of about 10 s for two periods of 30 min, having a break of 5 min in between. The sequence of the two experiments was randomized, and the study was single blinded. During the RF exposure, a GSM signal of 902.4 MHz (pulsed with 217 Hz) was applied to the subjects. The power flux density of the electromagnetic field at the subject location (in the absence of the subject) was 1 W/m(2), and numerical dosimetry calculations determined corresponding maximum local averaged specific absorption rate (SAR) values in the retina of SAR(1 g) = 0.007 W/kg and SAR(10 g) = 0.003 W/kg. No statistically significant differences in the VDThr were found in comparing the data obtained for RF exposure with those for sham exposure.
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Affiliation(s)
- Lars Irlenbusch
- Martin Luther University Halle, Department of Traumatology, Halle/Saale, Germany
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19
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Kozyreva TV, Lomakina SV, Tkachenko EY, Markel' AL. Effects of rapid and slow cooling on thermoregulatory reactions in hypertensive rats after administration of calcium. Neurosci Behav Physiol 2007; 37:19-26. [PMID: 17180314 DOI: 10.1007/s11055-007-0144-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Revised: 01/19/2005] [Indexed: 05/13/2023]
Abstract
Iontophoretic administration of calcium ions into the skin close to the application site of a cold stimulus decreased the threshold of thermoregulatory reactions in hypertensive rats to a greater extent than in normotensive control animals, which may be evidence that the tissues involved in thermoregulatory reactions to cold have a greater sensitivity to calcium in hypertensive rats. The initially earlier onset of vascular and metabolic reactions and the increase in the vascular reaction seen in hypertensive rats became more marked after administration of calcium. Treatment with calcium, increasing the vascular reaction to cooling, facilitates a more marked discrimination between hyper-and normotensive animals in terms of the appearance of the vasoconstrictor reactions of skin blood vessels in response to cold. The effects of the added calcium on cold-dependent reactions depended on the rate of cooling.
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Affiliation(s)
- T V Kozyreva
- Thermophysiology Laboratory, State Research Institute of Physiology, Siberian Branch, Russian Academy of Medical Sciences, Novosibirsk, Russia.
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Bäumer T, Demiralay C, Hidding U, Bikmullina R, Helmich RC, Wunderlich S, Rothwell J, Liepert J, Siebner HR, Münchau A. Abnormal plasticity of the sensorimotor cortex to slow repetitive transcranial magnetic stimulation in patients with writer's cramp. Mov Disord 2007; 22:81-90. [PMID: 17089385 DOI: 10.1002/mds.21219] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Previous studies demonstrated functional abnormalities in the somatosensory system, including a distorted functional organization of the somatosensory cortex (S1) in patients with writer's cramp. We tested the hypothesis that these functional alterations render S1 of these patients more susceptible to the "inhibitory" effects of subthreshold 1 Hz repetitive transcranial magnetic stimulation (rTMS) given to S1. Seven patients with writer's cramp and eight healthy subjects were studied. Patients also received rTMS to the motor cortex hand area (M1). As an outcome measure, short-latency afferent inhibition (SAI) was tested. SAI was studied in the relaxed first dorsal interosseous muscle using conditioning electrical stimulation of the index finger and TMS pulses over the contralateral M1. Baseline SAI did not differ between groups. S1 but not M1 rTMS reduced SAI in patients. rTMS had no effects on SAI in healthy subjects. Because SAI is mediated predominantly at a cortical level in the sensorimotor cortex, we conclude that there is an abnormal responsiveness of this area to 1 Hz rTMS in writer's cramp, which may represent a trait toward maladaptive plasticity in the sensorimotor system in these patients.
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Affiliation(s)
- Tobias Bäumer
- Department of Neurology, University of Hamburg, Hamburg, Germany
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21
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Abstract
Excitability measurements on human motor and sensory nerves have provided new insights into axonal membrane changes in peripheral nerve disorders. The aim of this study was to establish an in vivo rat preparation suitable for threshold tracking of sensory nerve action potentials (SNAPs) to model clinical sensory nerve excitability studies. In Sprague-Dawley rats anesthetized with ketamine and xylazine, current stimuli were applied to the base of the tail and SNAPs recorded from distal needle electrodes. Multiple excitability data were obtained as previously described for human nerves and compared to recordings from the motor tail axons and to sensory recordings from human median and ulnar nerves. The pattern of excitability changes in rats was broadly similar to that in humans, although some parameters differed significantly. Individual recordings were stable for at least 3 h. These data show that the rat tail enables excitability properties of sensory as well as motor axons to be studied experimentally, e.g., in models of nerve disease and during pharmacological interventions.
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Affiliation(s)
- Annette George
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
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22
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Fratello F, Veniero D, Curcio G, Ferrara M, Marzano C, Moroni F, Pellicciari MC, Bertini M, Rossini PM, De Gennaro L. Modulation of corticospinal excitability by paired associative stimulation: Reproducibility of effects and intraindividual reliability. Clin Neurophysiol 2006; 117:2667-74. [PMID: 17011821 DOI: 10.1016/j.clinph.2006.07.315] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2006] [Revised: 07/19/2006] [Accepted: 07/28/2006] [Indexed: 02/05/2023]
Abstract
OBJECTIVE Electrical stimulation of the median nerve followed by a magnetic pulse on the primary motor cortex (M1) is effective to cause an increase in the amplitude of motor evoked potential (MEP) registered in the target muscle with the interstimulus interval (ISI) at 25ms (paired associative stimulation, PAS). The aim of this study is to evaluate the reproducibility of PAS with ISI 25 (PAS25), assessed in two separate sessions. Intraindividual reliability of TMS measures was also evaluated. METHODS Motor threshold of abductor pollicis brevis (APB), assessed at rest, and MEP amplitude of APB and abductor digiti minimi (ADM) were assessed before and after PAS25 in 18 healthy volunteers (nine males and nine females). RESULTS Data showed a significant increase of MEP amplitude in the target muscle (APB) after PAS25 and a reproducibility of group effect in the two sessions, as assessed by ANOVA, but a lack of intraindividual reliability, as assessed by intraclass correlation coefficients (ICC). CONCLUSIONS The results underline the reproducibility of mean effects and the need to be careful when comparing the same subject on different days. SIGNIFICANCE Electrical stimulation of the median nerve followed by a magnetic pulse delivered on M1 after 25ms causes a reproducible increase in MEP amplitude, without showing an acceptable intraindividual reliability.
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Affiliation(s)
- Fabiana Fratello
- Department of Psychology, University of Rome, La Sapienza, Rome, Italy
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23
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Wang L, Zhang Y, Dai J, Yang J, Gang S. Electroacupuncture (EA) modulates the expression of NMDA receptors in primary sensory neurons in relation to hyperalgesia in rats. Brain Res 2006; 1120:46-53. [PMID: 17005164 DOI: 10.1016/j.brainres.2006.08.077] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 08/09/2006] [Accepted: 08/21/2006] [Indexed: 12/18/2022]
Abstract
N-methyl-D-aspartate (NMDA) receptor on the central terminals of the dorsal root ganglion (DRG) appears to be playing an important role in the development of central sensitization related to persistent inflammatory pain. Acupuncture analgesia has been confirmed by numerous clinical observations and experimental studies to be a useful treatment to release different kinds of pains, including inflammatory pain and hyperalgesia. However, the underlying mechanisms of the analgesic effect of acupuncture are not fully understood. In the present study, using a rat model of inflammatory pain induced by complete Freund's adjuvant (CFA), we observed the effect of electroacupuncture (EA) on animal behavior with regard to pain and the expression of a subunit of NMDA receptor (NR1) and isolectin B4 (IB4) in the neurons of the lumbar DRG. Intraplantar injection of 50 microl CFA resulted in considerable changes in thermal hyperalgesia, edema of the hind paw and "foot-bend" score, beginning 5 h post-injection and persisting for a few days, after which a gradual recovery occurred. The changes were attenuated by EA treatment received on the ipsilateral "Huan Tiao" and "Yang Ling Quan" once a day from the first day post-injection of CFA. Using an immunofluorescence double staining, we found that the number of double-labeled cells to the total number of the IB4 and NR1-labeled neurons increased significantly on days 3 and 7 after CFA injection. The change was attenuated by EA treatment. These results suggest that EA affects the progress of experimental inflammatory pain by modulating the expression of NMDA receptors in primary sensory neurons, in particular, IB4-positive small neurons.
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Affiliation(s)
- Lina Wang
- Department of Anesthesiology, The First Affiliated Hospital of Soochow University, Soochow 215006, China.
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24
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Zittel S, Bäumer T, Liepert J. Modulation of intracortical facilitatory circuits of the human primary motor cortex by digital nerve stimulation. Exp Brain Res 2006; 176:425-31. [PMID: 16951961 DOI: 10.1007/s00221-006-0624-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Accepted: 07/03/2006] [Indexed: 12/20/2022]
Abstract
We investigated the effect of electrical digit stimulation on two different intracortical facilitatory phenomena. Paired-pulse transcranial magnetic stimuli (TMS) with different conditioning stimulus (CS) intensities were applied over the primary motor cortex (M1). Electromyographic (EMG) recordings were made from the relaxed right abductor digiti minimi muscle (ADM). The effect of preceding sensory stimulation applied to the ipsilateral digit V on the conditioning magnetic stimulus was examined. Changing the CS intensity affected the influence of peripheral electrical stimulation on motor evoked potential (MEP) amplitudes evoked by paired pulse TMS. Inhibition induced by ipsilateral digit stimulation was strongest with the lowest CS intensity if MEP amplitudes were evoked by a subthreshold CS followed by a suprathreshold test stimulus (TS) at an interstimulus interval (ISI) of 10 ms. In contrast, inhibition induced by digit stimulation in a paired-pulse paradigm with a suprathreshold first and a subthreshold second stimulus at ISI of 1.5 ms was strongest with the highest CS intensity. These findings suggest that appropriately timed peripheral electrical stimuli differentially modulate facilitatory interactions in the primary motor cortex. They further support the hypothesis that intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF) are evoked through different mechanisms.
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Affiliation(s)
- Simone Zittel
- Department of Neurology, University Medical Center Eppendorf, Martinistr 52, 20246 Hamburg, Germany.
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25
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Moldovan M, Krarup C. Evaluation of Na+/K+ pump function following repetitive activity in mouse peripheral nerve. J Neurosci Methods 2006; 155:161-71. [PMID: 16466807 DOI: 10.1016/j.jneumeth.2005.12.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Revised: 11/02/2005] [Accepted: 12/19/2005] [Indexed: 10/25/2022]
Abstract
After conduction of prolonged trains of impulses the increased Na+/K+ pump activity leads to hyperpolarization. The aim of this study was to develop a mouse model to investigate the Na+/K+ pump function in peripheral nerve by measuring the decrease in excitability during activity-dependent hyperpolarization. Acute electrophysiological investigations were carried out in seven adult mice. Nerve excitability was evaluated by tracking the change in threshold current after 5 min of 100 Hz stimulation of the tibial nerve at ankle. We developed a threshold tracking system that allowed us to follow several excitability measures simultaneously from the evoked plantar compound muscle action potential (CMAP) and sciatic compound nerve action potential (CNAP). Three minutes after repetitive supramaximal stimulation maximal CMAP and CNAP amplitudes recovered but the threshold was increased approximately 40% for motor axons approximately 34% for axons generating CNAP. The threshold recovered with a rate of 3.8%/minute that was similar for nerve and motor responses. By tracking the effect of polarizing currents we found evidence of activity dependent hyperpolarization, and our data suggest that the observed threshold change after repetitive stimulation of the mouse tibial nerve is an indicator of the Na+/K+ pump function in vivo. Evaluation of activity-dependent hyperpolarization may be an important indicator of axonal ability to cope with Na+ load.
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Affiliation(s)
- Mihai Moldovan
- Division of Neurophysiology, Institute of Medical Physiology, Panum Institute, University of Copenhagen, Denmark
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26
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Abstract
To investigate peripheral nerve function and its potential contribution to symptoms of weakness in myotonic dystrophy type 1 (MD), nerve excitability was assessed in 12 MD patients. Compound muscle action potentials (CMAPs) were recorded at rest from abductor pollicis brevis (APB) following stimulation of the median nerve. Stimulus-response behavior, threshold electrotonus, a current-threshold relationship, and recovery cycles were successfully recorded in each patient. Compared with controls, there was significant reduction in CMAP amplitude in MD patients. This was accompanied by reduction in depolarizing threshold electrotonus and an increase in refractoriness and in the duration of the relative refractory period. To determine whether alteration in axonal resting membrane potential was a factor underlying these changes, axonal excitability was assessed following maximal contraction of APB for 60 seconds. Following contraction, there was reduction in CMAP amplitude for a submaximal stimulus (by 51.5+/-11.8%) and an increase in super-excitability (of 22.2+/-12.0%), consistent with activity-dependent hyperpolarization, with a greater increase in threshold for MD patients compared to controls (MD group, 22.3+/-5.1%; controls, 11.7+/-2.1%; P<0.04) and prolonged recovery to baseline. The present study has established that greater activity-dependent changes in excitability may be induced in MD patients by maximal voluntary contraction when compared to controls. The excitability changes and prolonged recovery of threshold following contraction are likely to contribute to symptoms of fatigue and weakness in MD patients.
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Affiliation(s)
- Arun V Krishnan
- Prince of Wales Medical Research Institute and Prince of Wales Clinical School, University of New South Wales, Barker Street, Randwick, Sydney, NSW 2031, Australia
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27
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Stuphorn V, Schall JD. Executive control of countermanding saccades by the supplementary eye field. Nat Neurosci 2006; 9:925-31. [PMID: 16732274 DOI: 10.1038/nn1714] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Accepted: 05/05/2006] [Indexed: 11/09/2022]
Abstract
The supplementary eye field registers the occurrence of conflict, errors and reward in macaque monkeys performing a saccade-countermanding task. Using intracortical microstimulation, we determined whether the supplementary eye field only monitors or can actually influence performance. Weak microstimulation of many sites in the supplementary eye field improved monkeys' performance on a 'stop signal' task by delaying saccade initiation. This effect depended on the context of the task because simple visually guided saccades were not delayed by the same stimulation. These results demonstrate that the supplementary eye field can exert contextual executive control over saccade generation.
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Affiliation(s)
- Veit Stuphorn
- Center for Integrative & Cognitive Neuroscience, Vanderbilt Vision Research Center, Department of Psychology, Vanderbilt University, Wilson Hall, 111 21st Avenue South, Nashville, Tennessee 37203, USA.
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28
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Dong XD, Mann MK, Sessle BJ, Arendt-Nielsen L, Svensson P, Cairns BE. Sensitivity of rat temporalis muscle afferent fibers to peripheral N-methyl-D-aspartate receptor activation. Neuroscience 2006; 141:939-945. [PMID: 16716525 DOI: 10.1016/j.neuroscience.2006.04.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 04/14/2006] [Accepted: 04/18/2006] [Indexed: 11/28/2022]
Abstract
The temporalis muscle is a common source of pain in headache and chronic craniofacial pain conditions such as temporomandibular disorders, which have an increased prevalence in women. The characteristics of slowly conducting temporalis afferent fibers have not been investigated. Therefore, the aim of the present study was to examine the characteristics of slowly conducting temporalis muscle afferent fibers and to determine whether these fibers are excited by activation of peripheral N-methyl-D-aspartate receptors. The response properties of a total of 117 temporalis afferent fibers were assessed in male and female rats. A majority of these fibers had high mechanical thresholds and slow conduction velocities (<10 m/s). The mechanical threshold of the temporalis afferent fibers was inversely correlated with afferent conduction velocity, however, no sex-related differences in mechanical threshold were identified. There were also no sex-related differences in N-methyl-D-aspartate-evoked afferent discharge. Indeed, injection of a high concentration (1600 mM) of N-methyl-D-aspartate into the temporalis muscle was necessary to evoke significant afferent discharge. Thirty minutes after the initial injection of N-methyl-D-aspartate into the temporalis muscle, a second injection of N-methyl-D-aspartate produced a response only about 50% as large as the initial injection. Co-injection of ketamine (20 mM) with the second injection of N-methyl-D-aspartate significantly decreased N-methyl-D-aspartate-evoked afferent discharge in both sexes. This concentration of ketamine is greater than that needed to attenuate afferent discharge evoked by injection of glutamate into the masseter muscle. These results suggest that unlike masseter afferent fibers, temporalis afferent fibers are relatively insensitive to peripheral N-methyl-D-aspartate receptor activation.
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Affiliation(s)
- X D Dong
- Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - M K Mann
- Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - B J Sessle
- Faculty of Dentistry, The University of Toronto, Toronto, Ontario, Canada M5G 1G6
| | - L Arendt-Nielsen
- Laboratory for Experimental Pain Research, Center for Sensory-Motor Interaction, Aalborg University, DK-9220 Aalborg, Denmark
| | - P Svensson
- Department of Clinical Oral Physiology, Dental School, Århus University, DK-8000 Århus C, Denmark
| | - B E Cairns
- Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T 1Z3.
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29
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Lepecq JC, De Waele C, Mertz-Josse S, Teyssèdre C, Huy PTB, Baudonnière PM, Vidal PP. Galvanic Vestibular Stimulation Modifies Vection Paths in Healthy Subjects. J Neurophysiol 2006; 95:3199-207. [PMID: 16436483 DOI: 10.1152/jn.00478.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study aimed at determining whether vestibular inputs contribute to the perception of the direction of self-motion. This question was approached by investigating the effects of binaural bipolar galvanic vestibular stimulation (GVS) on visually induced self-motion (i.e., vection) in healthy subjects. Stationary seated subjects were submitted to optokinetic stimulation inducing either forward or upward linear vection. While perceiving vection, they were administered trapezoidal GVS of different intensities and ramp durations. Subjects indicated the shape and direction of their perceived self-motion path throughout the experiment by a joystick, and after each trial by the manipulation of a 3D mannequin. Results show that: 1) GVS induced alterations of the path of vection; 2) these alterations occurred more often after GVS onset than after GVS offset; 3) the occurrence of vection path alterations after GVS onset depended on the intensity of GVS but not on the steepness of the GVS variation; 4) the vection path deviated laterally according to either an oblique or a curved path; and 5) the vection path deviated toward the cathode side after GVS onset. It is the first time that vestibular information, already known to contribute to the induction of vection, is shown to modify self-motion perception during the course of vection.
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Affiliation(s)
- Jean-Claude Lepecq
- Mouvement et Perception, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche (UMR) 6152 and Université de la Méditerranée, Faculté des Sciences du Sport, Marseille, France
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30
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Abstract
The sparsity of photons at very low light levels necessitates a nonlinear synaptic transfer function between the rod photoreceptors and the rod-bipolar cells. We examine different ways to characterize the performance of the pathway: the error rate, two variants of the mutual information, and the signal-to-noise ratio. Simulation of the pathway shows that these approaches yield substantially different performance at very low light levels and that maximizing the signal-to-noise ratio yields the best performance when judged from simulated images. The results are compared to recent data.
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Affiliation(s)
- Paul T Clark
- Institute for Adaptive and Neural Computation, School of Informatics, Edinburgh, EH1 2QL, UK.
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31
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Meredith MA, Keniston LR, Dehner LR, Clemo HR. Crossmodal projections from somatosensory area SIV to the auditory field of the anterior ectosylvian sulcus (FAES) in Cat: further evidence for subthreshold forms of multisensory processing. Exp Brain Res 2006; 172:472-84. [PMID: 16501962 DOI: 10.1007/s00221-006-0356-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Accepted: 12/30/2005] [Indexed: 10/25/2022]
Abstract
To date, evaluation of the neuronal basis for multisensory processing has focused on the convergence pattern that provides excitation from more than one sensory modality. However, a recent study (Dehner et al. in Cereb Cortex 14:387-401, 2004) has demonstrated excitatory-inhibitory multisensory effects that do not follow this conventional pattern and the present investigation documented a similar example of subthreshold cross-modal effects. Neuroanatomical tracers revealed that pyramidal neurons of the somatosensory area SIV project to the auditory field of the anterior ectosylvian sulcus (FAES), but subsequent electrophysiological tests showed that stimulation of SIV failed to elicit the expected orthodromic responses in FAES. Instead, combined auditory-SIV stimulation significantly suppressed FAES responses to auditory cues in approximately 25% of the neurons tested, and facilitated responses in another 5%. These modulatory responses in auditory FAES were similar in kind to those observed in somatosensory SIV and, as such, comprise further evidence for subthreshold forms of multisensory processing in cortex. Consequently, it seems likely that subthreshold cross-modal effects may impact other apparently 'unimodal' areas of the brain.
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Affiliation(s)
- M Alex Meredith
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
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32
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Yoo WK, Kim YH, Doh WS, Lee JH, Jung KI, Park DS, Park ES. Dissociable modulating effect of repetitive transcranial magnetic stimulation on sensory and pain perception. Neuroreport 2006; 17:141-4. [PMID: 16407760 DOI: 10.1097/01.wnr.0000198438.37012.d6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The effects of high frequency repetitive transcranial magnetic stimulation on sensory perception and the pain tolerance thresholds were investigated applying both motor cortex stimulation and medial frontal cortex stimulation in normal study participants. Both the sensory perception and pain tolerance thresholds were significantly increased in the motor cortex stimulation, whereas the pain tolerance thresholds, but not the sensory perception was significantly decreased in the medial frontal cortex stimulation. These results suggest the dissociable modulating effects of sensory and pain perception by the high frequency repetitive transcranial magnetic stimulation on the medial pain regulating system, but not the lateral pain regulating system.
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Affiliation(s)
- Woo-Kyoung Yoo
- Department of Physical Medicine and Rehabilitation Medicine, Hallym University Sacred Heart Hospital, Anyang, Republic of Korea
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33
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Nakajima T, Sakamoto M, Endoh T, Komiyama T. Location-specific and task-dependent modulation of cutaneous reflexes in intrinsic human hand muscles. Clin Neurophysiol 2006; 117:420-9. [PMID: 16376142 DOI: 10.1016/j.clinph.2005.09.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 09/18/2005] [Accepted: 09/23/2005] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The current study was designed to determine location-specificity in long latency cutaneous reflexes in intrinsic human hand muscles while performing a simple abduction and a manual task. METHODS Subjects comprised of 13 neurologically intact healthy volunteers. Cutaneous reflexes following non-noxious electrical stimulation to the digits of the hand (digit 1, D1; digit 2, D2; and digit 5, D5) were elicited while the subjects performed isolated isometric contraction of the abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi muscles (ADM). The cutaneous reflexes were also elicited while the subjects performed a pincer grip with D1 and D2 while slightly lifting the hand from the supporting surface by abduction of D5 (manual task). RESULTS While performing isolated tonic voluntary contraction of the APB, FDI and ADM, the magnitude of E2 (peak latency approximately 60-90 ms) was larger when stimulation was delivered to the homotopic digit (e.g. APB response following D1 stimulation) than to the heterotopic nearby (e.g. APB response following D2 stimulation) or heterotopic distant digit (e.g. APB response following D5 stimulation). I2 ( approximately 90-120 ms) and E3 ( approximately 120-180 ms) were significantly larger following D5 stimulation than D1 or D2 stimulation in all muscles tested. The size of each component in the ADM following D1 and D2 stimulation did not increase even when the contraction level of the ADM increased. However, while performing the manual task, the E2 response in the ADM following both D1 and D2 stimulation was significantly increased as compared to that recorded during isolated D5 abduction. CONCLUSIONS Long latency cutaneous reflexes following non-noxious electrical stimulation are organized in a highly location-specific as well as task-dependent manner. SIGNIFICANCE Our findings provide further insight into the nature and functional significance of long latency cutaneous reflexes in human intrinsic hand muscles.
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Affiliation(s)
- Tsuyoshi Nakajima
- Division of Health and Sports Education, United Graduate School of Education, Tokyo Gakugei University, 1-33 Yayoi-cho, Inage-Ku, Chiba City 263-8522, Japan
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Dickstein R, Laufer Y, Katz M. TENS to the posterior aspect of the legs decreases postural sway during stance. Neurosci Lett 2006; 393:51-5. [PMID: 16207512 DOI: 10.1016/j.neulet.2005.09.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Revised: 09/13/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
The purpose of this study was to examine the effect of Transcutaneous Electrical Nerve Stimulation (TENS) applied to the posterior aspect of the legs, on postural sway during stance. Thirty healthy subjects were tested while standing on a force platform under four stimulation conditions: no TENS, bilateral TENS, and unilateral left and right TENS. Thirty-second long tests, employing detection threshold amplitudes, were performed in three blocks. In each block, the four conditions were applied both with and without vision in a random order. The results indicate that the application of TENS brought about a decrease in postural sway as expressed by average sway velocity, in addition to a decrease in the absolute values of maximal and minimal medio-lateral and anterior-posterior velocity. Thus, similar to sub-threshold random electrical noise, it appears that the application of low-amplitude TENS to the lower limbs decreases postural sway during stance. Considering the ease of TENS application and the high prevalence of postural disorders, the potential clinical significance of this observation is to be determined by further studies.
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Affiliation(s)
- Ruth Dickstein
- Department of Physical Therapy, Faculty of Social Welfare and Health Studies, University of Haifa, Mount Carmel, Israel.
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Schiffmann R, Hauer P, Freeman B, Ries M, Scott LJC, Polydefkis M, Brady RO, McArthur JC, Wagner K. Enzyme replacement therapy and intraepidermal innervation density in Fabry disease. Muscle Nerve 2006; 34:53-6. [PMID: 16583374 DOI: 10.1002/mus.20550] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We prospectively evaluated the effect of enzyme replacement therapy (ERT) on the intraepidermal nerve fiber density (IENFD) and thermal threshold in patients with Fabry disease, an X-linked disorder associated with a painful small-fiber neuropathy and decreased linear IENFD in a length-dependent pattern. Twenty-five hemizygous male patients with Fabry disease were enrolled in a 6-month, randomized, placebo-controlled ERT trial of 0.2 mg/kg of alpha-galactosidase A (agalsidase-alfa) every 2 weeks followed by an additional 12 months of open-label ERT for both populations. IENFD and thermal threshold were measured in the distal thigh at baseline, 6 months, and 18 months from initiation of the trial. We found no significant difference in IENFD between the treatment groups at 6 months. After an additional year of ERT, there was a significant reduction in IENFD in the patient group as a whole, attributable to the declining glomerular filtration rate. Thermal thresholds remained unchanged. We conclude that epidermal nerve fiber regeneration, as measured in the distal thigh, does not occur in this patient population after 12-18 months of ERT.
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Affiliation(s)
- Raphael Schiffmann
- Developmental and Metabolic Neurology Branch, NINDS, National Institutes of Health, Bldg. 10, Room 3D03, 9000 Rockville Pike, Bethesda, Maryland 20892, USA.
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Harriott AM, Dessem D, Gold MS. Inflammation increases the excitability of masseter muscle afferents. Neuroscience 2006; 141:433-42. [PMID: 16690218 DOI: 10.1016/j.neuroscience.2006.03.049] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Revised: 03/24/2006] [Accepted: 03/28/2006] [Indexed: 11/16/2022]
Abstract
Temporomandibular disorder is a major health problem associated with chronic orofacial pain in the masticatory muscles and/or temporomandibular joint. Evidence suggests that changes in primary afferents innervating the muscles of mastication may contribute to temporomandibular disorder. However, there has been little systematic study of the mechanisms controlling the excitability of these muscle afferents, nor their response to inflammation. In the present study, we tested the hypotheses that inflammation increases the excitability of sensory neurons innervating the masseter muscle of the rat and that the ionic mechanisms underlying these changes are unique to these neurons. We examined inflammation-induced changes in the excitability of trigeminal ganglia muscle neurons following intramuscular injections of complete Freund's adjuvant. Three days after complete Freund's adjuvant injection acutely dissociated, retrogradely labeled trigeminal ganglia neurons were studied using whole cell patch clamp techniques. Complete Freund's adjuvant-induced inflammation was associated with an increase in neuronal excitability marked by a significant decrease in rheobase and increase in the slope of the stimulus response function assessed with depolarizing current injection. The increase in excitability was associated with significant decreases in the rate of action potential fall and the duration of the action potential afterhyperpolarization. These changes in excitability and action potential waveform were associated with significant shifts in the voltage-dependence of activation and steady-state availability of voltage-gated K(+) current as well as significant decreases in the density of voltage-gated K(+) current subject to steady-state inactivation. These data suggest that K(+) channel subtypes may provide novel targets for the treatment of pain arising from inflamed muscle. These results also support the hypothesis that the underlying mechanisms of pain arising from specific regions of the body are unique suggesting that it may be possible, if not necessary to treat pain originating from different parts of the body with specific therapeutic interventions.
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Affiliation(s)
- A M Harriott
- University of Maryland, Baltimore Dental School, Department of Biomedical Sciences, Room 5-A-12 HHH, 666 West Baltimore Street, Baltimore, MD 21201, USA
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Affiliation(s)
- Jens Ellrich
- Department of Neurosurgery, Experimental Neurosurgery, University Hospital Aachen, Pauwelsstrasse 30, D-52074 Aachen, Germany.
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Taguchi T, Sato J, Mizumura K. Augmented mechanical response of muscle thin-fiber sensory receptors recorded from rat muscle-nerve preparations in vitro after eccentric contraction. J Neurophysiol 2005; 94:2822-31. [PMID: 16160095 DOI: 10.1152/jn.00470.2005] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Unaccustomed strenuous exercise, especially that from eccentric muscular work, often causes muscle tenderness, which is a kind of mechanical hyperalgesia. We developed an animal model of delayed-onset muscle soreness (DOMS) from eccentric muscular contraction (ECC) in rats and demonstrated the existence of muscle tenderness by means of behavioral pain tests and c-Fos protein expression in the spinal dorsal horn. The purpose of the present study was to examine whether the sensitivities of muscle thin-fiber sensory receptors to mechanical, chemical, and thermal stimuli were altered after repetitive ECC in a rat model of DOMS. ECC was caused in the animals by electrical stimulation of the common peroneal nerve innervating the extensor digitorum longus muscle (EDL) while the muscle was being stretched. Activities of single thin-fiber receptors (sensitive to pressure but insensitive to stretch, with conduction velocity slower than 2.0 m/s) were recorded from muscle (EDL)-nerve preparations in vitro 2 days after ECC when mechanical hyperalgesia was at its peak. The mechanical threshold of thin-fiber receptors was found to be very much lower in the ECC preparations than in the nontreated control (CTR) [median 65.4 mN (interquartile range [IQR]; 46.6-122.0 mN) in the CTR preparation vs. 38.2 mN (IQR; 26.8-55.8 mN) in the ECC, P < 0.001]. In addition, the total number of evoked discharges during a ramp mechanical stimulus, taken as an index of the magnitude of the mechanical response, nearly doubled in the ECC preparations compared with the CTR [24.7 spikes (IQR; 14.2-37.1 spikes) in the CTR preparation vs. 54.2 spikes (IQR; 24.3-89.0 spikes) in the ECC, P < 0.001]. In contrast, the numbers of discharges induced by chemical (pH 5.5, lactic acid, adenosine triphosphate, and bradykinin) and thermal (cold and heat) stimuli were not different between the two preparations. These results suggest that augmentation of the mechanical response in muscle thin-fiber sensory receptors might be related to the muscle tenderness in DOMS after ECC.
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Affiliation(s)
- Toru Taguchi
- Department of Neural Regulation, Division of Regulation of Organ Function, Research Institute of Environmental Medicine, Nagoya, Japan
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Bajbouj M, Brakemeier EL, Schubert F, Lang UE, Neu P, Schindowski C, Danker-Hopfe H. Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex and cortical excitability in patients with major depressive disorder. Exp Neurol 2005; 196:332-8. [PMID: 16194530 DOI: 10.1016/j.expneurol.2005.08.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 07/21/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex is a relatively non-invasive technique with putative therapeutic effects in major depression. However, the exact neurophysiological basis of these effects needs further clarification. Therefore, we studied the impact of ten daily sessions of left, dorsolateral prefrontal rTMS on motor cortical excitability, as revealed by transcranial magnetic stimulation-elicited motor-evoked potentials in 30 patients. As compared to the non-responders, responders (33%) showed changes in parameters pointing towards a reduced cortical excitability. These results suggest that repetitive transcranial magnetic stimulation of the dorsolateral, prefrontal cortex may have inhibitory effects on motor cortical neuronal excitability in patients with major depressive disorder. Furthermore, measurement of motor cortical excitability may be a useful tool for investigating and monitoring inhibitory brain effects of antidepressant stimulation techniques like rTMS.
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Affiliation(s)
- Malek Bajbouj
- Department of Psychiatry, Charité-University Medicine Berlin, Campus Benjamin Franklin, Eschenallee 3, 14050 Berlin, Germany.
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Abstract
This study investigates motor (MNCS) and sensory (SNCS) nerve conduction in a sample of non-diabetic obese people without symptoms suggestive of neuropathy and looks for a possible metabolic alteration. Twenty-one patients and 20 age-matched controls underwent (a) MNCS (median, ulnar, peroneal, and tibial) and SNCS (median, ulnar, and sural); (b) quantitative sensory testing to measure sensory threshold for vibration, warm and cold sensation (WS-CS), heat and cold-induced pain; and (c) blood sample analysis to evaluate glucose and insulin levels and calculate the quantitative insulin-sensitivity check index (QUICKI). The obese group showed significantly decreased compound muscle action potential amplitude of tibial and peroneal nerves and decreased sensory action potential amplitude of all nerves. Most of the sensory thresholds were altered in obese patients. Insulin serum levels were significantly increased while QUICKI decreased in obese patients. WS and CS from the index and little fingers and WS from the big toe significantly correlated with QUICKI. Thermal and pain thresholds from the index and thermal thresholds from the little finger correlated with QUICKI values. The non-diabetic obese patients showed a subclinical involvement of different diameter sensory fibers. Such impairment was related to hyperinsulinemia and insulin sensitivity. The increase in sensory threshold of obese patients might be due to a metabolic alteration, potentially leading to a future clinical neuropathy.
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Affiliation(s)
- Giacinta Miscio
- Department of Neurology, Istituto Auxologico Italiano, IRCCS, San Giuseppe Hospital, Strada L. Cadorna 90, 28824 Piancavallo- Oggebbio VB, Italy.
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Hölscher T, Seibt A, Appold S, Dörr W, Herrmann T, Hüttenbrink KB, Hummel T. Effects of radiotherapy on olfactory function. Radiother Oncol 2005; 77:157-63. [PMID: 16226328 DOI: 10.1016/j.radonc.2005.09.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Revised: 08/26/2005] [Accepted: 09/26/2005] [Indexed: 11/19/2022]
Abstract
BACKGROUND AND PURPOSE Changes in olfactory function have been reported in patients receiving significant doses of radiation to the olfactory epithelium. Aim of this study was to investigate severity and time course of changes in olfactory function in patients irradiated for tumours of the head and neck region. MATERIAL AND METHODS Forty-four patients receiving radiotherapy (RT) for tumours in the area of the head and neck participated (16 women, 28 men; age 11-81 y; mean 55 y). Olfactory function was measured before and bi-weekly during RT for 6 weeks. A subgroup (25 patients) was followed for 12 months. Patients were divided into two groups according to the dose to the olfactory epithelium. Twenty-two patients ('OLF group') had radiation doses to the olfactory epithelium between 23.7 and 79.5 Gy (median 62.2 Gy). In the 22 patients of the 'non-OLF group' the dose applied to the olfactory epithelium was significantly lower (2.9-11.1 Gy, median 5.9 Gy). Total tumour dose (30-76.8 Gy), age, sex distribution, and baseline chemosensory function were not significantly different between groups. Testing was performed for odour identification, odour discrimination, and olfactory thresholds. RESULTS Odour discrimination, but not odour identification or odour threshold, was significantly decreased 2-6 weeks after begin of therapy in the OLF group. In addition, a significant effect of the radiation dose was observed for odour discrimination. More than 6 months after therapy, OLF group patients had significantly lower odour identification scores compared to the non-OLF group. CONCLUSION As indicated through the non-significant change of olfactory thresholds, the olfactory epithelium is relatively resistant against effects of radiation. It is hypothesized that RT has additional effects on the olfactory bulb/orbitofrontal cortex responsible for the observed changes of suprathreshold olfactory function.
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Affiliation(s)
- Tobias Hölscher
- Department of Radiotherapy and Radiation Oncology, Medical Faculty Carl Gustav Carus, University of Technology, Dresden, Germany
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Tammpere A, Brusberg M, Axenborg J, Hirsch I, Larsson H, Lindström E. Evaluation of pseudo-affective responses to noxious colorectal distension in rats by manometric recordings. Pain 2005; 116:220-226. [PMID: 15936885 DOI: 10.1016/j.pain.2005.04.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 03/24/2005] [Accepted: 04/08/2005] [Indexed: 12/30/2022]
Abstract
Recordings of electromyographic (EMG) activity in the abdominal musculature are generally used to quantify the pseudo-affective visceromotor response induced by colorectal distension (CRD) in rodents. The present study describes a non-invasive, manometric method to quantify the magnitude of the abdominal contractions evoked by CRD. CRD-induced increases in EMG activity in female rats (electrical response) were compared to phasic changes in balloon pressure (mechanical response). A phasic increasing CRD paradigm from 10 to 80mmHg with 10mmHg intervals induced a clear stimulus-response relationship with a strong correlation (r(2)=0.93) between the electrical and mechanical responses. Twelve repeated phasic distensions at 80mmHg increased the mechanical response by 133+/-53% (P<0.01), while the electrical response only increased by 20+/-19% (P>0.05), when comparing the last distension to the first. Atropine methyl bromide (1mg/kg, i.v.) did not affect the mechanical response to distension at 80mmHg, suggesting that colonic activity per se, does not contribute to the balloon pressure variations during CRD in the current experimental set-up. The mu-opioid receptor agonist fentanyl at a dose of 1.5microg/kg (i.v.) significantly reduced the mechanical response to CRD (P<0.01) while the electrical response was not affected. The present study shows that phasic bursts in EMG activity from the abdominal musculature occur simultaneously with balloon pressure variations, which may represent a non-invasive alternative to EMG recordings. Furthermore, the mechanical response is a more sensitive parameter for detecting both hyperalgesic and analgesic responses.
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Affiliation(s)
- Anna Tammpere
- AstraZeneca R&D, Integrative Pharmacology, GI Biology, S-431 83 Mölndal, Sweden AstraZeneca R&D, Discovery IS/IT, S-431 83 Mölndal, Sweden
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Abstract
This study investigates whether the right hemisphere has more flexible contrast gain control settings for the identification of spatial frequency. Right-handed participants identified 1 and 9 cycles per degree sinusoidal gratings presented either to the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH). When luminance contrast was randomized across a wide range (20-60%), performance gradually improved with contrast in the LVF-RH. Conversely, performance in the RVF-LH was disrupted and saturated for 20 and 60% of contrast, respectively, leading to a LVF-RH advantage for these contrast levels. When contrast was blocked or randomized for a smaller range (30-50%), the LVF-RH advantage was diminished. Flexible contrast gain control is needed when contrast is randomized across a wide range, but not when it is blocked or randomized across a smaller range. The results therefore suggest that the right hemisphere is able to process spatial frequency information across a wider range of contrast levels than is the left hemisphere.
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Affiliation(s)
- Matia Okubo
- Department of Psychology, University of Melbourne, Australia.
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Troup LJ, Pitts MA, Volbrecht VJ, Nerger JL. Effect of stimulus intensity on the sizes of chromatic perceptive fields. J Opt Soc Am A Opt Image Sci Vis 2005; 22:2137-42. [PMID: 16277283 DOI: 10.1364/josaa.22.002137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The effects of intensity on chromatic perceptive field size were investigated along the horizontal meridian at 10 degrees temporal eccentricity by manipulating stimulus intensity from 0.3 to 3.3 log trolands. Following light adaptation, observers described the hue and saturation of monochromatic stimuli (440-660 nm, in 10 nm steps) for a series of test sizes (0.098-3 degrees) presented along the time period associated with the cone plateau of the dark-adaptation function. Perceptive field sizes of the four elemental hues (red, green, yellow, and blue) and the saturation component were estimated by three observers at each intensity level for each wavelength. In general, perceptive field sizes of blue and red are the smallest, and yellow and green are the largest. Furthermore, perceptive field sizes of all four hues decrease with increasing stimulus intensity, though the absolute change is largest for green and yellow. The decrease in size with increase in intensity cannot be completely explained in terms of saturation or rod signals and is likely, then, attributable to a cone-based mechanism.
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Affiliation(s)
- Lucy J Troup
- Department of Psychology, Colorado State University, Fort Collins 80523, USA.
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Boers J, Ford TW, Holstege G, Kirkwood PA. Functional Heterogeneity Among Neurons in the Nucleus Retroambiguus With Lumbosacral Projections in Female Cats. J Neurophysiol 2005; 94:2617-29. [PMID: 15972831 DOI: 10.1152/jn.00370.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nucleus retroambiguus (NRA), in the caudal medulla, projects to all spinal levels. One physiological role is abdominal pressure control, evidenced by projections to intercostal and abdominal motoneurons from expiratory bulbospinal neurons (EBSNs) within NRA. The roles of NRA projections to the lumbosacral cord are less certain, although those to limb motoneurons may relate to mating behavior and those to Onuf's nucleus (ON) to maintaining continence. To clarify this we physiologically characterized NRA projections to the lumbosacral cord. Extracellular recordings were made in NRA under anesthesia and paralysis in estrus cats. Administered CO2gave a strong respiratory drive. Antidromic unit responses were recorded to stimulation of the contralateral ventrolateral funiculus of L6, L7, or sacral segments and to microstimulation in the region of semimembranosus motor nucleus or ON. All units were found at sites showing expiratory discharges. Units that showed collisions between antidromic and spontaneous spikes (all in late expiration) were identified as EBSNs. These were common from the ventrolateral funiculus (VLF) of L6(42.5%) or L7(32.9%), but rare from the sacral VLF or the motor nuclei. Antidromic latencies revealed a subthreshold respiratory drive in some non-EBSNs. This group had lower conduction velocities than the EBSNs. The remainder, with a negligible respiratory drive, had even lower conduction velocities. A new population of NRA neurons has thus been defined. They are not active even with a strong respiratory drive, but may provide most of the synaptic input from NRA to lower lumbar and sacral segments and could subserve functions related to mating behavior.
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Affiliation(s)
- J Boers
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, UK
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Kashima K, Watanabe N, Higashinaka S, Maeda S, Shiba R. Changes in sensory and pain perception thresholds after linear polarized near-infrared light radiation in the trigeminal region. Cranio 2005; 23:174-8. [PMID: 16128351 DOI: 10.1179/crn.2005.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Linearly polarized light in the near-infrared portion of the spectrum has recently been associated with a variety of musculoskeletal disorders including temporomandibular disorders. The purpose of this study was to determine whether short-term linearly polarized near-infrared light radiation in the trigeminal region affects sensory and pain perception thresholds in the trigeminally mediated region and in the cervically mediated region of normal subjects. Thirty-five normal female volunteers participated in this study. Each subject received an 8-minute course of irradiation in the right cheek, and sensory/nociceptive perception thresholds were compared before and immediately after the irradiation in the right cheek and the right forearm. As a result, this study demonstrated a significant elevation of the heat-induced pain threshold in both regions and a tendency for the warm sensation threshold to elevate in the cervical region. In addition, a significant increase in vibratory sensitivity was observed in the trigeminal region. In conclusion, our results provided additional evidence that the warming sensation has a negative feedback influence on heat pain intensity in humans, and provides a theoretical basis for the application of linear polarized near-infrared light radiation to the trigeminal region.
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Affiliation(s)
- Koji Kashima
- Department of Oral and Maxillofacial Surgery, Miyazaki Medical College, Hyotake-cho, Miyazaki, Japan.
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Helmich RCG, Bäumer T, Siebner HR, Bloem BR, Münchau A. Hemispheric asymmetry and somatotopy of afferent inhibition in healthy humans. Exp Brain Res 2005; 167:211-9. [PMID: 16034577 DOI: 10.1007/s00221-005-0014-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Accepted: 03/31/2005] [Indexed: 10/25/2022]
Abstract
A conditioning electrical stimulus to a digital nerve can inhibit the motor-evoked potentials (MEPs) in adjacent hand muscles elicited by transcranial magnetic stimulation (TMS) to the contralateral primary motor cortex (M1) when given 25-50 ms before the TMS pulse. This is referred to as short-latency afferent inhibition (SAI). We studied inter-hemispheric differences (Experiment 1) and within-limb somatotopy (Experiment 2) of SAI in healthy right-handers. In Experiment 1, conditioning electrical pulses were applied to the right or left index finger (D2) and MEPs were recorded from relaxed first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles ipsilateral to the conditioning stimulus. We found that SAI was more pronounced in right hand muscles. In Experiment 2, electrical stimulation was applied to the right D2 and MEPs were recorded from ipsilateral FDI, extensor digitorum communis (EDC) and biceps brachii (BB) muscles. The amount of SAI did not differ between FDI, EDC and BB muscles. These data demonstrate inter-hemispheric differences in the processing of cutaneous input from the hand, with stronger SAI in the dominant left hemisphere. We also found that SAI occurred not only in hand muscles adjacent to electrical digital stimulation, but also in distant hand and forearm and also proximal arm muscles. This suggests that SAI induced by electrical D2 stimulation is not focal and somatotopically specific, but a more widespread inhibitory phenomenon.
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Affiliation(s)
- R C G Helmich
- Department of Neurology, Radboud University Nijmegen Medical Centre, The Netherlands
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Abstract
Focal electric stimulation of the auditory cortex, 30-min repetitive acoustic stimulation, and auditory fear conditioning each evoke shifts of the frequency-tuning curves [hereafter, best frequency (BF) shifts] of cortical and collicular neurons. The short-term collicular BF shift is produced by the corticofugal system and primarily depends on the relationship in BF between a recorded collicular and a stimulated cortical neuron or between the BF of a recorded collicular neuron and the frequency of an acoustic stimulus. However, it has been unknown whether focal electric stimulation of the inferior colliculus evokes the collicular BF shift and whether the collicular BF shift, if evoked, depends on corticofugal feedback. In our present research with the awake big brown bat, we found that focal electric stimulation of collicular neurons evoked the BF shifts of collicular neurons located near the stimulated ones; that there were two types of BF shifts: centripetal and centrifugal BF shifts, i.e., shifts toward and shifts away from the BF of stimulated neurons, respectively; and that the development of these collicular BF shifts was blocked by inactivation of the auditory cortex. Our data indicate that the collicular BF shifts (plasticity) evoked by collicular electric stimulation depended on corticofugal feedback. It should be noted that collicular BF shifts also depend on acetylcholine because it has been demonstrated that atropine (an antagonist of muscarinic acetylcholine receptors) applied to the IC blocks the development of collicular BF shifts.
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Affiliation(s)
- Yongkui Zhang
- Department of Biology, Washington University, St. Louis, MO 63130, USA
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Sauer SK, Weidner C, Carr RW, Averbeck B, Nesnidal U, Reeh PW, Handwerker HO. Can Receptor Potentials Be Detected With Threshold Tracking in Rat Cutaneous Nociceptive Terminals? J Neurophysiol 2005; 94:219-25. [PMID: 15772238 DOI: 10.1152/jn.00655.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Threshold tracking of individual polymodal C- and Aδ-fiber terminals was used to assess membrane potential changes induced by de- or hyperpolarizing stimuli in the isolated rat skin–nerve preparation. Constant current pulses were delivered (1 Hz) through a tungsten microelectrode inserted in the receptive field, and the current amplitude was controlled by feedback with a laboratory computer programmed to serially determine the electrical threshold using the method of limits. During threshold tracking, the receptive fields of the fibers were heated (32–46°C in 210 s) or superfused with modified synthetic interstitial fluid containing either 0, 20, 40, 50, or 60 mM [K+], phosphate buffer to pH 5.2 or 6.1, or bradykinin (BK, 10−8–10-5 M). High [K+]e decreased the current threshold for activation by 6–14% over 120 s, whereas K+-free superfusion augmented the threshold by >5%, and after some delay, also induced ongoing discharge in 60% of units. pH 6.1 and 5.2 caused an increase in threshold of 6 and 18%, respectively, and 30% of the fibers were excited by low pH, although the change in threshold of pH responsive and unresponsive fibers did not differ significantly, suggesting a general excitability decrease induced by protons. Heat stimulation increased the mean threshold and conduction velocity of the fibers tested and resulted in activity in 78% of units. Additionally, for these units, activation was preceded by a significant decrease in threshold compared with the tracked thresholds of fibers unresponsive to heat. Bradykinin also led to a significant threshold decrease before activation. In conclusion, the technique of threshold tracking proved suitable to assess changes in excitability resulting from receptor currents evoked by noxious heat and bradykinin in the terminal arborization of cutaneous nociceptors.
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Affiliation(s)
- S K Sauer
- Department of Physiology and Pathophysiology, University of Erlangen/Nürnberg, Erlangen, Germany.
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Garcia AMB, Cardenas FP, Morato S. Effect of different illumination levels on rat behavior in the elevated plus-maze. Physiol Behav 2005; 85:265-70. [PMID: 15927214 DOI: 10.1016/j.physbeh.2005.04.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 03/31/2005] [Accepted: 04/04/2005] [Indexed: 11/19/2022]
Abstract
The present study addressed the role of environmental light intensity on the exploratory behavior of rats in the elevated plus-maze, with the specific goal of determining the light intensity threshold for triggering the aversion to the open arms. Male Wistar-derived rats were tested in the elevated plus-maze under different illumination levels: 0, 1, 3, 10, 30, 100 and 300 lx. Exploratory behavior occurring in the open arms (e.g., entries and time spent in these arms) was more intense under 0 and 1 lx than under the other illumination levels, which did not differ among themselves; on the other hand, locomotor behavior (as indicated by frequency of entries and distance run in the closed arms) was not altered under all illumination conditions. The data indicated that vision is important in triggering aversion to the open arms of the elevated plus-maze. They also indicated that the threshold of such aversion was found between 1 and 3 lx environmental illumination and that the phenomena is not intensity-dependent but rather of an all-or-none type. It should be emphasized that these conclusions only stand for unfamiliar environments. The role of light in familiar environments is currently under investigation in our laboratory.
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Affiliation(s)
- Andrea Milena Becerra Garcia
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto-USP, Av Bandeirantes, 3900, 14049-901 Ribeirão Preto-SP, Brazil
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