Abstract
C. elegans neuronal system constitutes the ideal framework for studying simple, yet realistic, neuronal activity, since the whole nervous system is fully characterized with respect to the exact number of neurons and the neuronal connections. Most recent efforts are devoted to investigate and clarify the signal processing and functional connectivity, which are at the basis of sensing mechanisms, signal transmission, and motor control. In this framework, a refined modelof whole neuron dynamics constitutes a key ingredient to describe the electrophysiological processes, both at thecellular and at the network scale. In this work, we present Hodgkin-Huxley-based models of ion channels dynamics black, built on data available both from C. elegans and from other organisms, expressing homologous channels. We combine these channel models to simulate the electrical activity oftwo among the most studied neurons in C. elegans, which display prototypical dynamics of neuronal activation, the chemosensory AWCON and the motor neuron RMD. Our model properly describes the regenerative responses of the two cells. We analyze in detail the role of ion currents, both in wild type and in in silico knockout neurons. Moreover, we specifically investigate the behavior of RMD, identifying a heterogeneous dynamical response which includes bistable regimes and sustained oscillations. We are able to assess the critical role of T-type calcium currents, carried by CCA-1 channels, and leakage currents in the regulation of RMD response. Overall, our results provide new insights in the activity of key C. elegans neurons. The developed mathematical framework constitute a basis for single-cell and neuronal networks analyses, opening new scenarios in the in silico modeling of C. elegans neuronal system.
Highlights
Mfx, mmx, msx denote fast, medium and slow component, respectively, of activating variable associated to the x channel, while τmf x, τmmx, τms x denote the corresponding time constants
Data obtained from these equations are reported in the corresponding panels of Figs 1, 2, 3, and S1, S2, S3, S5 Figs
Ca stands for the micro-scale calcium concentration, i.e. the intracellular calcium
Summary
For each modeled channel x, equations for steady-state activation and inactivation curves, time constants and current are reported below. Mfx, mmx , msx (hfx, hmx , hsx) denote fast, medium and slow component, respectively, of activating (inactivating) variable associated to the x channel, while τmf x , τmmx , τms x (τhf x , τhmx , τhsx ) denote the corresponding time constants. Data obtained from these equations are reported in the corresponding panels of Figs 1, 2, 3, and S1, S2, S3, S5 Figs. E c +e e hfSHL1,∞(V ) = hsSHL1,∞(V ) =
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