Similar activity patterns at both neuron and network levels can arise from different combinations of membrane and synaptic conductance values. A strategy by which neurons may preserve their electrical output is via cell type-dependent balances of inward and outward currents. Measurements of mRNA transcripts that encode ion channel proteins within motor neurons in the crustacean cardiac ganglion recently revealed correlations between certain channel types. To determine whether balances of intrinsic currents potentially resulting from such correlations preserve certain electrical cell outputs, we developed a nominal biophysical model of the crustacean cardiac ganglion using biological data. Predictions from the nominal model showed that coregulation of ionic currents may preserve the key characteristics of motor neuron activity. We then developed a methodology of sampling a multidimensional parameter space to select an appropriate model set for meaningful comparison with variations in correlations seen in biological datasets.

Franklin CC, Ball JM, Schulz DJ, Nair SS. Generation and preservation of the slow underlying membrane potential oscillation in model bursting neurons. J Neurophysiol 104: 1589 -1602, 2010. First published June 30, 2010 doi:10.1152/jn.00444.2010. The underlying membrane potential oscillation of both forced and endogenous slowwave bursting cells affects the number of spikes per burst, which in turn affects outputs downstream. We use a biophysical model of a class of slow-wave bursting cells with six active currents to investigate and generalize correlations among maximal current conductances that might generate and preserve its underlying oscillation. We propose three phases for the underlying oscillation for this class of cells: generation, maintenance, and termination and suggest that different current modules coregulate to preserve the characteristics of each phase. Coregulation of I Burst and I A currents within distinct boundaries maintains the dynamics during the generation phase. Similarly, coregulation of I CaT and I Kd maintains the peak and duration of the underlying oscillation, whereas the calcium-activated I KCa ensures appropriate termination of the oscillation and adjusts the duration independent of peak.

Homeostatic processes are widespread throughout all living systems, and the nervous system is no exception. Individual neurons as well as neuronal networks must maintain levels of excitability and connectivity to ensure that consistent functional output is achieved. Possible mechanisms for maintaining functional output using co-regulation of channel conductances is studied for a motor neuron, using a computational model. The results are both consistent with and extend the biological observations.