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Whole-cell Current-clamp Recordings (whole-cell + current-clamp_recording)
Selected AbstractsRole of Ca2+ -Activated Cl, Current in Ventricular Action Potentials of Sheep During Adrenoceptor StimulationEXPERIMENTAL PHYSIOLOGY, Issue 2 2001Arie O. Verkerk Adrenoceptor stimulation enhances repolarising and depolarising membrane currents to different extents in cardiac myocytes. We investigated the opposing effects of the repolarising Ca2+ -activated Cl, current (ICl(Ca)) and depolarising L-type Ca2+ current (ICa,L) on the action potential configuration of sheep ventricular myocytes stimulated with noradrenaline. Whole-cell current-clamp recordings revealed that noradrenaline accelerated and prolonged phase-1 repolarisation. We define the minimal potential at the end of phase-1 repolarisation as ,notch level'. Noradrenaline (1 ,M) caused the notch level to fall from 14 ± 2.6 to 7.8 ± 2.8 mV (n= 24), but left action potential duration, resting membrane potential or action potential amplitude unaffected. Whole-cell voltage-clamp recordings showed that 1 ,M noradrenaline increased both ICa,L and ICl(Ca), but it had no significant effect on the principal K+ currents. Blockage of ICl(Ca) by 0.5 mM 4,4,-diisothiocyanatostilbene-2,2,-disulphonic acid (DIDS) in both the absence and the presence of noradrenaline abolished phase-1 repolarisation. In the presence of noradrenaline, DIDS caused elevation of the plateau phase amplitude and an increase in the action potential duration. In conclusion, elevation of the plateau phase amplitude and action potential prolongation associated with an increased ICa,L upon adrenoceptor stimulation is prevented by an increased ICl(Ca) in sheep ventricular myocytes. [source] Nesfatin-1 Influences the Excitability of Paraventricular Nucleus NeuronesJOURNAL OF NEUROENDOCRINOLOGY, Issue 2 2008C. J. Price Nesfatin-1 is a newly-discovered satiety peptide found in several nuclei of the hypothalamus, including the paraventricular nucleus. To begin to understand the physiological mechanisms underlying these satiety-inducing actions, we examined the effects of nesfatin-1 on the excitability of neurones in the paraventricular nucleus. Whole-cell current-clamp recordings from rat paraventricular nucleus neurones showed nesfatin-1 to have either hyperpolarising or depolarising effects on the majority of neurones tested. Both types of response were observed in neurones irrespective of classification based on electrophysiological fingerprint (magnocellular, neuroendocrine or pre-autonomic) or molecular phenotype (vasopressin, oxytocin, corticotrophin-releasing hormone, thyrotrophin-releasing hormone or vesicular glutamate transporter), determined using single cell reverse transcription-poylmerase chain reaction. Consequently, we provide the first evidence that this peptide, which is produced in the paraventricular nucleus, has effects on the membrane potential of a large proportion of different subpopulations of neurones located in this nucleus, and therefore identify nesfatin-1 as a potentially important regulator of paraventricular nucleus output. [source] Activation of a calcium entry pathway by sodium pyrithione in the bag cell neurons of AplysiaDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2004Ronald J. Knox Abstract The ability of sodium pyrithione (NaP), an agent that produces delayed neuropathy in some species, to alter neuronal physiology was accessed using ratiometric imaging of cytosolic free Ca2+ concentration ([Ca2+]i) in fura PE-filled cultured Aplysia bag cell neurons. Bath-application of NaP evoked a [Ca2+]i elevation in both somata and neurites with an EC50 of ,300 nM and a Hill coefficient of ,1. The response required the presence of external Ca2+, had an onset of 3,5 min, and generally reached a maximum within 30 min. 2-Methyl-sulfonylpyridine, a metabolite and close structural analog of NaP, did not elevate [Ca2+]i. Under whole-cell current-clamp recording, NaP produced a ,14 mV depolarization of resting membrane potential that was dependent on external Ca2+. These data suggested that NaP stimulates Ca2+ entry across the plasma membrane. To minimize the possibility that a change in cytosolic pH was the basis for NaP-induced Ca2+ entry, bag cell neuron intracellular pH was estimated with the dye 2,,7,-bis(carboxyethyl-5(6)-carboxy-fluorescein acetoxy methylester. Exposure of the neurons to NaP did not alter intracellular pH. The slow onset and sustained nature of the NaP response suggested that a cation exchange mechanism coupled either directly or indirectly to Ca2+ entry could underlie the phenomenon. However, neither ouabain, a Na+/K+ ATPase inhibitor, nor removal of extracellular Na+, which eliminates Na+/Ca2+ exchanger activity, altered the NaP-induced [Ca2+]i elevation. Finally, the possibility that NaP gates a Ca2+ -permeable ion channel in the plasma membrane was examined. NaP did not appear to activate two major forms of bag cell neuron Ca2+ -permeable ion channels, as Ca2+ entry was unaffected by inhibition of voltage-gated Ca2+ channels using nifedipine or by inhibition of a voltage-dependent, nonselective cation channel using a high concentration of tetrodotoxin. In contrast, two potential store-operated Ca2+ entry current inhibitors, SKF-96365 and Ni2+, attenuated NaP-induced Ca2+ entry. We conclude that NaP activates a slow, persistent Ca2+ influx in Aplysia bag cell neurons. © 2004 Wiley Periodicals, Inc. J Neurobiol 411,423, 2004 [source] Topographical projection from the superior colliculus to the nucleus of the brachium of the inferior colliculus in the ferret: convergence of visual and auditory informationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000Timothy P. Doubell Abstract The normal maturation of the auditory space map in the deeper layers of the ferret superior colliculus (SC) depends on signals provided by the superficial visual layers, but it is unknown where or how these signals influence the developing auditory responses. Here we report that tracer injections in the superficial layers label axons with en passant and terminal boutons, both in the deeper layers of the SC and in their primary source of auditory input, the nucleus of the brachium of the inferior colliculus (nBIC). Electron microscopy confirmed that biocytin-labelled SC axons form axodendritic synapses on nBIC neurons. Injections of biotinylated dextran amine in the nBIC resulted in anterograde labelling in the deeper layers of the SC, as well as retrogradely labelled superficial and deep SC neurons, whose distribution varied systematically with the rostrocaudal placement of the injection sites in the nBIC. Topographical order in the projection from the SC to the ipsilateral nBIC was confirmed using fluorescent microspheres. We demonstrated the existence of functional SC-nBIC connections by making whole-cell current-clamp recordings from young ferret slices. Both monosynaptic and polysynaptic EPSPs were generated by electrical stimulation of either the superficial or deep SC layers. In addition to unimodal auditory units, both visual and bimodal visual,auditory units were recorded in the nBIC in vivo and their incidence was higher in juvenile ferrets than in adults. The SC-nBIC circuit provides a potential means by which visual and other sensory or premotor signals may be delivered to the nBIC to calibrate the representation of auditory space. [source] | ||||||||||