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L-type Ca channels contain a cluster of four charged glutamate residues (EEEE locus), which seem essential for high Ca specificity. To understand how this highly charged structure might produce the currents and selectivity observed in this channel, a theory is needed that relates charge to current. We use an extended Poisson-Nernst-Planck (PNP2) theory to(More)
The ionic permeability of a voltage-dependent Cl channel of rat hippocampal neurons was studied with the patch-clamp method. The unitary conductance of this channel was approximately 30 pS in symmetrical 150 mM NaCl saline. Reversal potentials interpreted in terms of the Goldman-Hodgkin-Katz voltage equation indicate a Cl:Na permeability ratio of(More)
Motor endplates of frog semitendinosus muscles were studied under voltage clamp. Current fluctuations induced by iontophoretic application of acetylcholine were analyzed to give the elementary conductance, gamma , and mean open time, tau , of endplate channels. Total replacement of the external Na+ ion by several other metal ions and by many permeant(More)
The molecular identity of non-Cav1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca2+-dependent functions is indisputable. Recently, a transient Cav3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in(More)
1. Sodium currents (INa) and asymmetrical displacement currents (ID) were measured in the same nerve fibres from Rana esculenta under similar conditions. 2. For exploring possible kinetic and steady state relations between INa and ID the following quantities were compared: (i) the activation of the sodium channels and (ii) the charge displacement of ID. 3.(More)
1. Single, voltage-clamped nerve fibres of Rana esculenta were stimulated with ;P/2' pulse patterns for measuring Na and gating currents at 13 degrees C.2. Gating currents during test pulses to - 122 or + 10 mV were measured after 45 msec conditioning steps to voltages between - 122 and - 18 mV. As the conditioning voltage was made more positive than - 80(More)
Background Cl channels in neurons and skeletal muscle are significantly permeable for alkali cations when tested with asymmetrical concentrations of the same salt. Both anion and cation permeation were proposed to require binding of an alkali cation with the pore (Franciolini, F., and W. Nonner. 1987. Journal of General Physiology. 90:453-478). We tested(More)
We studied the permeation properties of two distinct single voltage-gated Ca2+ channels in bullfrog saccular hair cells to assess the roles of the channels as physiological Ca2+ transporters and multi-ion pores. By varying the permeant ions (Ba2+, Ca2+) and concentrations (2-70 mM), we estimated the affinity constant (K(D)) of the two channels as follows(More)
The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing voltage-clamp pulses of identical size. Since 1. the integrals of the "on" and "off" current transients were found to be equal and opposite,(More)
The drift-diffusion (Poisson-Nernst-Planck) model is applied to ionic channels in biological membranes plus surrounding solution baths. Simulations of the K channel in KCl solutions using the TRBDF2 method are presented which show significant boundary layers at the ends of the channel. The computed current-voltage curve for the K channel shows excellent(More)