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Robert F Schmidt - One of the best experts on this subject based on the ideXlab platform.
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morphine microinjected into the Nucleus tractus solitarius and rostral ventrolateral Medullary Nucleus enhances somatosympathetic a and c reflexes in anesthetized rats
Neuroscience Letters, 1996Co-Authors: Akio Sato, Yuko Sato, Robert F SchmidtAbstract:Abstract The modulatory effects of morphine microinjected into localized areas of the brainstem on somatosympathetic A- and C-reflexes were examined in urethane-anesthetized rats. Somatosympathetic A- and C-reflexes were elicited in a branch of the inferior cardiac nerve by electrical stimulation of myelinated (A) and unmyelinated (C) afferent fibers in the tibial nerve. Morphine (0.002–0.2 μg/50 nl) was microinjected into the rostral, intermediate and caudal parts of the Nucleus tractus solitarius (NTS), the rostral ventrolateral Medullary Nucleus (RVLM), the caudal ventrolateral Medullary Nucleus (CVLM), the locus coeruleus (LC), the raphe magnus (RM), the periaqueductal gray (PAG), and the accumbens Nucleus (Acb). Microinjections of morphine (0.2 μg) into the intermediate and caudal NTS produced significant augmentations of the A- and C-reflexes, C-reflexes being more markedly enhanced than A-reflexes. Microinjection of morphine (0.2 μg) into the RVLM produced a prominent increase in the C-reflex, the threshold dose for a significant increase being 0.02 μg morphine. Microinjection of morphine up to 0.2 μg/50 nl into the other areas mentioned above had no significant effect on either reflex component. All opiate-induced increases of the reflex discharges could be reversed by intravenous application of naloxone (2 mg/kg). The reflex augmentation induced by microinjection of morphine into the NTS may be caused by suppressing inhibitory baroreceptor information or by enhancing excitatory chemoreceptor information in the NTS. Augmentation of the C-reflex induced by microinjection of morphine into the RVLM may be caused by facilitating C-reflex pathways or by suppressing inhibitory neural circuits involved in the C-reflex within the RVLM.
Albert S Feng - One of the best experts on this subject based on the ideXlab platform.
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heterogeneous biophysical properties of frog dorsal Medullary Nucleus cochlear Nucleus neurons
Journal of Neurophysiology, 2007Co-Authors: Sungchil Yang, Albert S FengAbstract:The cochlear Nucleus (CN) in mammals, or its counterpart in birds, has multiple subdivisions each containing distinct morphological and functional (i.e., temporal discharge patterns and biophysical...
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phase locked response characteristics of single neurons in the frog cochlear Nucleus to steady state and sinusoidal amplitude modulated tones
Journal of Neurophysiology, 1994Co-Authors: Albert S Feng, Wenyu LinAbstract:1. We made extracellular recordings from 164 single neurons in the frog dorsal Medullary Nucleus (DMN), a homologue of the cochlear Nucleus. Phase-locked responses to tones at the unit's characteristic frequency (CF) and to off-CF tones were evaluated. We also stimulated units with tones at CF that were amplitude modulated sinusoidally between 5 and 1,000 Hz and examined responses to these stimuli. 2. Results showed that single neurons in the frog DMN displayed phase-locked discharges to tones at frequencies < or = 800 Hz. Phase-locking was robust at low frequencies (< 400 Hz) and became poorer at higher frequencies; the variation of the synchronization coefficient (SC) with frequency typically showed a low-pass characteristic. 3. The capacity of phase-locking to tones was correlated with the functional classification of a DMN neuron and the firing rate of its CF response. Primarylike neurons exhibited various degrees of phase-locked discharges to tones at off-CF frequencies. The average upper cutoff frequency, i.e., the frequency at which the SC dropped to 0.5 of maximum value, differed for the three classes of primarylike neurons. The average cutoff frequency was respectively 183, 325, and 536 Hz for primarylike neurons that displayed low (PL-1), intermediate (PL-2), and high (PL-3) steady-state firing rates to CF stimulation. The phasic neurons showed poor phase-locking capacities at all tone frequencies. 4. The frequency range of phase-locking to amplitude-modulated stimuli was also different for the different cell types, as evidenced by the units' modulation transfer functions (MTFs). The primarylike neurons exhibited mostly all-pass or low-pass sync-based MTFs. The mean upper cutoff frequencies for primarylike neurons having low-pass MTFs were 155 Hz for PL-1 neurons, 176 Hz for PL-2 neurons, and 218 Hz for PL-3 neurons. Pauser, chopper, phasic, and phasic-burst neurons gave mostly low-pass MTFs having a mean upper cutoff frequency of 219, 235, 242, and 251 Hz, respectively. 5. The phase-locking ability of DMN neurons to tones and to amplitude-modulated stimuli are compared with those of frog's primary afferent fibers and with those of avian and mammalian cochlear Nucleus neurons. The significance of results in terms of sound localization and sound pattern recognition is discussed.
Jakob Christensendalsgaard - One of the best experts on this subject based on the ideXlab platform.
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tone and call responses of units in the auditory nerve and dorsal Medullary Nucleus of xenopus laevis
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2007Co-Authors: Jakob Christensendalsgaard, Taffeta M Elliott, Darcy B KelleyAbstract:The clawed frog Xenopus laevis produces vocalizations consisting of distinct patterns of clicks. This study provides the first description of spontaneous, pure-tone and communication-signal evoked discharge properties of auditory nerve (n.VIII) fibers and dorsal Medullary Nucleus (DMN) cells in an obligatorily aquatic anuran. Responses of 297 n.VIII and 253 DMN units are analyzed for spontaneous rates (SR), frequency tuning, rate-intensity functions, and firing rate adaptation, with a view to how these basic characteristics shape responses to recorded call stimuli. Response properties generally resemble those in partially terrestrial anurans. Broad tuning exists across characteristic frequencies (CFs). Threshold minima are -101 dB re 1 mm/s at 675 Hz; -87 dB at 1,600 Hz; and -61 dB at 3,000 Hz (-90, -77, and -44 dB re 1 Pa, respectively), paralleling the peak frequency of vocalizations at 1.2-1.6 kHz with approximately 500 Hz in 3 dB bandwidth. SRs range from 0 to 80 (n.VIII) and 0 to 73 spikes/s (DMN). Nerve and DMN units of all CFs follow click rates in natural calls, < or =67 clicks/s and faster. Units encode clicks with a single spike, double spikes, or bursts. Spike times correlate closely with click envelopes. No temporal filtering for communicative click rates occurs in either n.VIII or the DMN.
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binaural interaction in the frog dorsal Medullary Nucleus
Brain Research Bulletin, 2005Co-Authors: Jakob Christensendalsgaard, Morten KanneworffAbstract:We have studied binaural and directional processing in cells in the frog dorsal Medullary Nucleus (DMN) stimulated with dichotic sound (couplers) and free-field sound. We present evidence that already at this stage of central processing the neural directionality is sharpened, probably by binaural interaction. Binaural interaction in the DMN was usually interpreted as inhibition, mostly driven from the contralateral side and dependent on a certain combination of interaural time differences (ITD) and interaural level differences (ILD). In free-field measurements, the strength and timing of the binaural inputs will depend on sound direction as processed by the auditory fibers. Thus, the directionality of DMN cells is caused by both monaural directional cues generated by acoustical coupling of the eardrums and non-tympanic pathways as well as binaural interaction. Most DMN cells show ovoidal directional characteristics and the directionality is sharpened compared to that of auditory nerve fibers. We suggest that the sharpening is due to the inhibitory interactions.
Morten Kanneworff - One of the best experts on this subject based on the ideXlab platform.
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binaural interaction in the frog dorsal Medullary Nucleus
Brain Research Bulletin, 2005Co-Authors: Jakob Christensendalsgaard, Morten KanneworffAbstract:We have studied binaural and directional processing in cells in the frog dorsal Medullary Nucleus (DMN) stimulated with dichotic sound (couplers) and free-field sound. We present evidence that already at this stage of central processing the neural directionality is sharpened, probably by binaural interaction. Binaural interaction in the DMN was usually interpreted as inhibition, mostly driven from the contralateral side and dependent on a certain combination of interaural time differences (ITD) and interaural level differences (ILD). In free-field measurements, the strength and timing of the binaural inputs will depend on sound direction as processed by the auditory fibers. Thus, the directionality of DMN cells is caused by both monaural directional cues generated by acoustical coupling of the eardrums and non-tympanic pathways as well as binaural interaction. Most DMN cells show ovoidal directional characteristics and the directionality is sharpened compared to that of auditory nerve fibers. We suggest that the sharpening is due to the inhibitory interactions.
Akio Sato - One of the best experts on this subject based on the ideXlab platform.
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morphine microinjected into the Nucleus tractus solitarius and rostral ventrolateral Medullary Nucleus enhances somatosympathetic a and c reflexes in anesthetized rats
Neuroscience Letters, 1996Co-Authors: Akio Sato, Yuko Sato, Robert F SchmidtAbstract:Abstract The modulatory effects of morphine microinjected into localized areas of the brainstem on somatosympathetic A- and C-reflexes were examined in urethane-anesthetized rats. Somatosympathetic A- and C-reflexes were elicited in a branch of the inferior cardiac nerve by electrical stimulation of myelinated (A) and unmyelinated (C) afferent fibers in the tibial nerve. Morphine (0.002–0.2 μg/50 nl) was microinjected into the rostral, intermediate and caudal parts of the Nucleus tractus solitarius (NTS), the rostral ventrolateral Medullary Nucleus (RVLM), the caudal ventrolateral Medullary Nucleus (CVLM), the locus coeruleus (LC), the raphe magnus (RM), the periaqueductal gray (PAG), and the accumbens Nucleus (Acb). Microinjections of morphine (0.2 μg) into the intermediate and caudal NTS produced significant augmentations of the A- and C-reflexes, C-reflexes being more markedly enhanced than A-reflexes. Microinjection of morphine (0.2 μg) into the RVLM produced a prominent increase in the C-reflex, the threshold dose for a significant increase being 0.02 μg morphine. Microinjection of morphine up to 0.2 μg/50 nl into the other areas mentioned above had no significant effect on either reflex component. All opiate-induced increases of the reflex discharges could be reversed by intravenous application of naloxone (2 mg/kg). The reflex augmentation induced by microinjection of morphine into the NTS may be caused by suppressing inhibitory baroreceptor information or by enhancing excitatory chemoreceptor information in the NTS. Augmentation of the C-reflex induced by microinjection of morphine into the RVLM may be caused by facilitating C-reflex pathways or by suppressing inhibitory neural circuits involved in the C-reflex within the RVLM.