Research Interests: Neuroscience, Psychology, Enzyme Inhibitors, Vestibular System, Nitric oxide, and 14 moreAnimals, Synaptic Transmission, Coefficient of Variation, Sensory Coding, Nitric Oxide Synthase, SYNAPSES, Penicillamine, NITRIC ACID, Action Potentials, Ambystoma, Neurosciences, Methyl Ester, Nitric oxide donors, and Excitatory Postsynaptic Potentials
Conus californicus belongs to a genus of marine gastropods with more than 700 extant species. C. californicus has been shown to be distantly related to all Conus species, but showing unusual biological features. We report a novel peptide... more
Conus californicus belongs to a genus of marine gastropods with more than 700 extant species. C. californicus has been shown to be distantly related to all Conus species, but showing unusual biological features. We report a novel peptide isolated from C. californicus with a significant inhibitory action over neuronal voltage-gated calcium channels. The new toxin is formed by 13-amino acid residues with two disulfide bonds, whose sequence (NCPAGCRSQGCCM) is strikingly different from regular ω-conotoxins. In the HPLC purification procedure, the venom fraction eluted in the first 10–15 min produced a significant decrease (54% ± 3%) of the Ca2+ current in Xenopus laevis oocytes transfected with purified rat-brain mRNA. A specific peptide obtained from the elution at 13 min decreased the Ca2+ current in the adult rat dorsal-root ganglion neurons in a primary culture by 34% ± 2%. The cysteine pattern of this peptide corresponds to the framework XVI described for the M-superfamily of conopeptides and is unprecedented among Conus peptides acting on Ca2+ channels.
Research Interests: Psychology, Cognitive Science, Electrophysiology, Kinetics, Plant Biology, and 62 moreNeuroendocrinology, Plant cell physiology, Calcium, Ion Channels, Patch-clamp and imaging techniques, Electrocardiography, Biological Sciences, Dogs, Hippocampus, Glutamate, Virtual screening, Blood Pressure, Female, Animals, Heart rate, Heart, Osmotic pressure, Calcium Channel, Molecular docking, Central Nervous System, Potassium, Rat Brain, Snails, Neurons, Steady state, High Pressure Liquid Chromatography, Rats, Gadolinium, Voltage-Gated Potassium Channels, Xenopus laevis, Potassium Channels, Tetrodotoxin, Amino Acid Profile, Tetraethylammonium, Transfection, Action potential, Molecular weight, Primary Culture, Rabbits, Imidazoles, Amino Acid Sequence, Membrane Potential, Action Potentials, Oocytes, Voltage Clamp, Nifedipine, Hydrogen-Ion Concentration, Neurosciences, Toxicon, Potassium Chloride, Time Course, Patch Clamp, Biochemistry and cell biology, Molecular Structure, Biomechanical Phenomena, Calcium Channel Blockers, Glutamate Receptor, Chara, Disulfide bond, Depolarization, Molecular Sequence Data, and Cell Membrane
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Research Interests: Immunology, Pain, Inflammation, Animals, Male, and 6 moreAnalgesia, Aminoglycosides, Rats, Wistar Rats, Pain Measurement, and Nociceptors
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Extracellular protons have been shown to modulate voltage-activated ionic channels. It has been proposed that synaptic modulation by exocytosed vesicular protons would be a characteristic feature of ribbon-type synapses. Type-I hair cells... more
Extracellular protons have been shown to modulate voltage-activated ionic channels. It has been proposed that synaptic modulation by exocytosed vesicular protons would be a characteristic feature of ribbon-type synapses. Type-I hair cells have a calyceal afferent junction with a diffusionally restricted synaptic cleft. These led us to study the action of extracellular pH changes on the voltage-activated Ca2+ and K+ currents evaluated using a whole-cell patch clamp in isolated cells. The amplitude of the Ca2+ and the K+ current were reduced by extracellular acidification, but without significant changes with extracellular alkalization. A shift in the voltage dependence to a more positive membrane potential was achieved at pH + and Ca2+ currents are modulated by protons, indicating that protons released along with an afferent neurotransmitter would participate as a feedback mechanism in type-I hair cells.
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Research Interests: Psychology, Cognitive Science, Electrophysiology, Kinetics, Plant Biology, and 62 moreNeuroendocrinology, Plant cell physiology, Calcium, Ion Channels, Patch-clamp and imaging techniques, Electrocardiography, Biological Sciences, Dogs, Hippocampus, Glutamate, Virtual screening, Blood Pressure, Female, Animals, Heart rate, Heart, Osmotic pressure, Calcium Channel, Molecular docking, Central Nervous System, Potassium, Rat Brain, Snails, Neurons, Steady state, High Pressure Liquid Chromatography, Rats, Gadolinium, Voltage-Gated Potassium Channels, Xenopus laevis, Potassium Channels, Tetrodotoxin, Amino Acid Profile, Tetraethylammonium, Transfection, Action potential, Molecular weight, Primary Culture, Rabbits, Imidazoles, Amino Acid Sequence, Membrane Potential, Action Potentials, Oocytes, Voltage Clamp, Nifedipine, Hydrogen-Ion Concentration, Neurosciences, Toxicon, Potassium Chloride, Time Course, Patch Clamp, Biochemistry and cell biology, Molecular Structure, Biomechanical Phenomena, Calcium Channel Blockers, Glutamate Receptor, Chara, Disulfide bond, Depolarization, Molecular Sequence Data, and Cell Membrane
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This study aimed to define the acute electrophysiological effects of the perilymphatic perfusion of streptomycin in the sensory apparatus of the semicircular canals of the frog. The ampullary DC potential, the vestibular nerve multiunit... more
This study aimed to define the acute electrophysiological effects of the perilymphatic perfusion of streptomycin in the sensory apparatus of the semicircular canals of the frog. The ampullary DC potential, the vestibular nerve multiunit discharge, the nerve DC potential and the unitary EPSP activity were recorded in isolated semicircular canals of the frog (Rana esculenta L). The results demonstrated that perilymphatic microperfusion of streptomycin (0.1, 0.3, 1 and 3 mM) reduced both resting and mechanically evoked afferent discharge, while the response of the hair cells remains unchanged. Intracellular recordings from single afferent axons showed that the reduction of the afferent discharge was mainly due to a reduction of the amplitude, but not the frequency, of the EPSPs. These results indicate that streptomycin, when applied in the fluid bathing the synaptic pole of the sensory cells, can act as an antagonist of the vestibular afferent transmitter at the postsynaptic level.
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In the search for new glutamate antagonists it seems promising to characterize the effects of venom from invertebrates that prey mainly on crustaceans. In this work, the exudate of the sea anemone Phyllactis flosculifera was used as a... more
In the search for new glutamate antagonists it seems promising to characterize the effects of venom from invertebrates that prey mainly on crustaceans. In this work, the exudate of the sea anemone Phyllactis flosculifera was used as a source of this type of compound. The action of Chromatographic fraction D from P. flosculifera was tested upon microion- tophoretically evoked glutamate responses in intracellular recordings from central neurons of the land snail Zachrysia guanensis. Bath application of fraction D (2–8 mg/ml, n = 13) diminished both the excitatory and the inhibitory components of glutamate agonists in Z. guanensis neurons; this action was dose-dependent and partially reversible. Fraction D actions were also tested in the multiunit spontaneous and mechanically evoked responses of the glutamatergic junction between hair cells and afferent neurons of the axolotl Ambystoma tigrinum. Pressure ejection of fraction D in concentrations ranging from 0.5 to 2 mg/ml (n = 9) decreased the spontaneous and mechanically evoked activity of semicircular canal afferent neurons and the responses evoked by kainic acid and α-amino-3-hydroxy-5-methylisoxasole-4-propionic acid. This action was also dose-dependent and partially reversible. These results indicate that fraction D acts as a glutamate receptor antagonist in snail and amphibian neurons. Further studies are required to characterize the active compounds responsible for this action and its specificity upon the subtypes of glutamate receptors.
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Research Interests: Cognitive Science, Calcium, Patch-clamp and imaging techniques, Vestibular System, Brain, and 13 moreNitric oxide, Animals, Calcium channels, Calcium Channel, Inner Ear, Steady state, Rats, Transmitter release, Electric Conductivity, Neurosciences, NIMODIPINE, Calcium Channel Blockers, and Low voltage
This study was undertaken to determine the possible role of GABA as an afferent transmitter in the vestibular system of the axolotl. We studied the effects of GABA, muscimol, bicuculline and picrotoxin on the spontaneous spike discharge... more
This study was undertaken to determine the possible role of GABA as an afferent transmitter in the vestibular system of the axolotl. We studied the effects of GABA, muscimol, bicuculline and picrotoxin on the spontaneous spike discharge of the afferent fibers of the sacculi lagena and anterior semicircular canal. It was found that GABA and muscimol produce a very weak excitatory effect which does not mimic either the temporal course or the amplitude of the response of vestibular afferents to physiological stimuli. The GABA antagonist bicuculline has no significant effect on these fibers, and picrotoxin partially blocks the spontaneous activity in 33% of the fibers studied. These results indicate that GABA is probably not an afferent transmitter in the vestibular system as has previously been proposed.
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We studied the effects of BgK toxin on outward K+ currents in isolated neurons of the snail Helix aspersa, using the whole cell patch clamp technique. BgK partially and reversibly blocked K+ currents in the 1 pM to 100 nM concentration... more
We studied the effects of BgK toxin on outward K+ currents in isolated neurons of the snail Helix aspersa, using the whole cell patch clamp technique. BgK partially and reversibly blocked K+ currents in the 1 pM to 100 nM concentration range (n=53). The dose–response curve for BgK current inhibition had a maximum blocking effect at 100 nM. Our results indicate that BgK is a potent, apparently non-selective, K+ channel blocker in molluscan neurons.
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A Turbo Pascal program for data acquisition and analysis is presented. The program detects incoming data as TTL pulses through the serial port of an IBM-PC and compatible computers and displays the instantaneous frequency plot and the... more
A Turbo Pascal program for data acquisition and analysis is presented. The program detects incoming data as TTL pulses through the serial port of an IBM-PC and compatible computers and displays the instantaneous frequency plot and the interval histogram on-line. Novel features of this Pascal program are: (1) no special hardware requirements and (2) on-line analysis of more than one source at a time. No hardware additions to the supplied computer and easy operation make this program a valuable tool, directly useable in an IBM-PC and compatible computers.
Research Interests: Cognitive Science, Vestibular System, Software, Evoked Potentials, Computer Systems, and 14 moreAnimals, Data acquisition, Interval analysis, Microcomputers, Neuronal Activity, Biological Process, Action potential, Microcomputer, Action Potentials, IBM PC, Statistical Methods for Neuroscience, Ambystoma, Neurosciences, and Instantaneous frequency
It has been suggested that streptomycin might be an antagonist of the glutamate receptors, and that it selectively blocks quisqualic acid receptors. We studied whether streptomycin blocks the responses to excitatory amino acid agonists on... more
It has been suggested that streptomycin might be an antagonist of the glutamate receptors, and that it selectively blocks quisqualic acid receptors. We studied whether streptomycin blocks the responses to excitatory amino acid agonists on the vestibular system primary afferents, and if it allows us to differentiate between kainate (KA) and quisqualate (QA) receptor mediated responses. The experiments were performed in the axolotl (Ambystoma tigrinum). Intra- and extracellular records of the electrical activity of semicircular canal afferent fibers were obtained. Drugs were applied by pressure ejection in volumes of 20 μl in a 10 ml bath. Streptomycin (0.01–10 mM), induced a dose dependent reversible inhibition of the basal spike discharge of the afferent fibers. This coincided with a reduction in the amplitude of excitatory postsynaptic potentials (EPSP) recorded recorded intracellularly in the afferent fibers. Streptomycin also blocked the excitatory action produced by KA and QA; increasing concentrations of streptomycin produced a rightward shift in the concentration-response curves for both KA and QA. This action persisted even in a high Mg2+ (10 mM), low Ca2+ (0.09 mM) Ringer solution, indicating its postsynapsic nature. These results show that streptomycin might be a non-selective excitatory amino acid (EAA) receptor antagonist.
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A system for on-line spike detection and analysis based on an IBM™ PC/AT compatible computer, written in TURBO PASCAL™ 6.0 and using commercially available analog-to-digital hardware is described here. Spikes are detected by an adaptive... more
A system for on-line spike detection and analysis based on an IBM™ PC/AT compatible computer, written in TURBO PASCAL™ 6.0 and using commercially available analog-to-digital hardware is described here. Spikes are detected by an adaptive threshold which varies as a function of signal mean and its variability. Since the threshold value is determined automatically by the signal-to-noise ratio analysis, the user is not actively involved in controlling its level. This program has been reliably used for the detection and analysis of the spike discharge of vestibular system afferent neurons. It generates the interval-joint distribution graph, the interval histogram, the autocorrelation function, the autocorrelation histogram, and phase-space graphs, thus, providing a complete set of graphical and statistical data for the characterization of the dynamics of neuronal spike activity. Data can be exported to other software such as Excel™, Sigmaplot™ and MatLab™, for example.
Research Interests: Engineering, Computer Graphics, Dynamical Systems, Medical Informatics, Neurophysiology, and 19 moreVestibular System, Spike train analysis, Software, Evoked Potentials, Humans, Animals, Data Display, Reaction Time, Synaptic Transmission, Online Systems, Microcomputers, Phase Space, Dynamic System, Single Unit Recording, Signal to Noise Ratio, Ambystoma, Autocorrelation Function, Adaptive Thresholding, and Data Acquisition System
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Research Interests: Engineering, Computer Graphics, Dynamical Systems, Medical Informatics, Neurophysiology, and 19 moreVestibular System, Spike train analysis, Software, Evoked Potentials, Humans, Animals, Data Display, Reaction Time, Synaptic Transmission, Online Systems, Microcomputers, Phase Space, Dynamic System, Single Unit Recording, Signal to Noise Ratio, Ambystoma, Autocorrelation Function, Adaptive Thresholding, and Data Acquisition System
We report the existence and anatomical distribution to nociceptin/orphanin-FQ (N/O FQ)-like immunoreactivity in neurons and fibers in the perioesophageal ganglia of the snail (Helix aspersa). Intracellular recordings from perioesophageal... more
We report the existence and anatomical distribution to nociceptin/orphanin-FQ (N/O FQ)-like immunoreactivity in neurons and fibers in the perioesophageal ganglia of the snail (Helix aspersa). Intracellular recordings from perioesophageal ganglion neurons showed that the application of 10 μM N/O FQ produced an excitatory action in 22% of the neurons studied and an inhibitory action in 33% of the neurons regardless of their origin (cerebral or parietal ganglion). Our result provides evidence that N/O FQ-like peptide is located in whole perioesophageal ganglia (mainly in the cerebral one), and that it may serve as a neuromodulator of the neuronal spike discharge. These data support the idea that the N/O FQ opioid system has an early phylogenetic origin and a functional continuity during the course of evolution.