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INFLUENCE OF DIFFERENT MODELING PROTOCOLS FOR CALCIUM CURRENTS IN THE AHP FEATURES OF A TYPE-S MOTONEURON

2013; Frontiers Media; Volume: 7; Linguagem: Inglês

10.3389/conf.fninf.2013.09.00083

1662-5196

Fernandes Evlyn, Vieira Marcus,

Muscle activation and electromyography studies

Event Abstract Back to Event INFLUENCE OF DIFFERENT MODELING PROTOCOLS FOR CALCIUM CURRENTS IN THE AHP FEATURES OF A TYPE-S MOTONEURON Evlyn D. Fernandes1* and Marcus F. Vieira1 1 Federal University of Goiás, School of Electrical, Mechanical and Computer Engineering, Brazil A mathematical model of a type S motoneuron (MN) was developed to evaluate the influence of different modeling protocols for calcium currents and calcium reversal potential in the soma of the MN. The dendritic tree was modeled as a passive structure with a stem cylinder and two asymmetrical branches using a tapering cable model (Figure 1). Ionic channels in soma were associated with the leakage, delayed-rectifier potassium, calcium-dependent potassium (SK), sodium fast, hyperpolarizing, A current, N-type and P-type calcium-currents, according to the Hogdkin-Huxley (HH) formalism (Hogdkin and Huxley, 1952). The parameters were adjusted to represent the physiological responses of cat motoneurons (Zengel et al., 1985). The calcium currents were modeled with the HH formalism and a reversal potential for calcium set as 140 mV (HHEs model). Then, the reversal potential was calculated according to the Nernst equation (HHEv model). This change resulted in a magnitude decrease of the AHP in response to a current pulse in the soma of 50 nA and 0.5 ms of duration, but still within the values reported in experimental data. This is due to the decrease in the calcium drive potential (ECa –Vs) and hence a decrease in the calcium current, intracellular calcium concentration and in the potassium SK, responsible for the AHP. It was also built two models using the Goldman-Hodgkin-Katz (GHK) (Goldman, 1943; Hodgkin and Katz, 1949) formalism for the calcium currents: one with AHP values with the same magnitude of HHEs (0.040% of difference – model GHKEs) and another with the same as in HHEv (0.042% of difference – model GHKEv). The magnitude of the currents (type-P and type-N calcium, potassium SK) were similar (<1%, except for the type-N in the HHEv and GHKEv, which was 6.92% different), but the time course was different. The N-type calcium currents of the GHK models have a rising time ≈ 25% larger than the correspondent HH models and a half-decay time ≈ 23% larger (Figure 2A). The type-P calcium current have a rising time ≈ 39% larger and a half-decay time ≈ 14% larger (Figure 2B). The same happens with the variables that depend on the calcium concentration. Using GHK or HH formalism in the passive model altered the time course of the currents, but it did not affect the final behavior of the model. Legend Figure 1: Geometry of the type-S MN model. The SI is the cylinder representing the initial segment, a spherical soma, a stem dendrite and two asymmetric branch, with 10 and 8 cylinders. Legend Figure 2:Type-N (A) and type-P (B) calcium currents in response for a current pulse of 50 nA and 0.5 ms of duration applied in the soma. Figure 1 Figure 2 Acknowledgements The authors are grateful tothe Brazilian Research Council of Technological and Scientific Development (CNPQ) for financial support. The first author acknowledges the scholarship given by CAPES foundation - Brazil. References Goldman, D.E. (1943). Potential impedance and rectification in membranes. J. Gen. Physiol. 27, 37-60. Hodgkin, A.L., Huxley, A.F. (1952). A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. 117, 500-544. Hodgkin, A.L., Katz, B. (1949). The effect of sodium ions on the electrical activity of the giant axon of the squid. J. Physiol. 108, 37-77. Zengel, J.E., Reid, S.A., Sypert, G.W., Munson, J.B. (1985). Membrane Electrical-Properties and Prediction of MotorUnit Type of Medial Gastrocnemius Motoneurons in the Cat. J. Neurophysiol. 53, 1323-1344. Keywords: Motoneuron models, Calcium Channels, Calcium currents, compartimental models, GHK equation Conference: Neuroinformatics 2013, Stockholm, Sweden, 27 Aug - 29 Aug, 2013. Presentation Type: Poster Topic: Computational neuroscience Citation: Fernandes ED and Vieira MF (2013). INFLUENCE OF DIFFERENT MODELING PROTOCOLS FOR CALCIUM CURRENTS IN THE AHP FEATURES OF A TYPE-S MOTONEURON. Front. Neuroinform. Conference Abstract: Neuroinformatics 2013. doi: 10.3389/conf.fninf.2013.09.00083 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Apr 2013; Published Online: 11 Jul 2013. * Correspondence: Miss. Evlyn D Fernandes, Federal University of Goiás, School of Electrical, Mechanical and Computer Engineering, Goiania, Goias, 74605-010, Brazil, evlynx@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. 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