Calcium sensor properties for activity-dependent homeostatic regulation of pyloric network rhythms in the lobster stomatogastric ganglion

• ¹ University of Zagreb, United States

Homeostatic regulation has been proposed as a mechanism that can explain the robust behavior of central pattern generating (CPG) neural networks observed experimentally. CPG networks, such as the pyloric network in the stomatogastric ganglion (STG) of the lobster, generate stable patterns of activity in spite of constant molecular turnover and environmental changes. Although the sensing and acting components of regulation are not yet well understood, one likely scenario is that calcium-based activity sensors drive the regulation of intrinsic cellular and synaptic properties. It has been shown that calcium can help maintain stable activity levels in individual model neurons [1], and pyloric rhythms in one network model [2]. Remaining questions are: (1) whether calcium sensors work in different network model versions, and (2) what intrinsic properties of calcium sensors are important for distinguishing functional from non-functional activity patterns. We tested an existing database of about 20 million simplified pyloric networks, constructed by varying the three lateral pyloric (LP), pyloric (PY) and anterior burster and pyloric dilator (AB/PD) neuron models and their synaptic strengths [3], to see if calcium sensors can distinguish functional pyloric activity. A set of three sensors---a fast (F), slow (S) and DC (D) sensor---in each neuron, could classify 88% of the networks correctly as functional or non-functional. To find properties necessary for these sensors, we constructed a set of 354 sensors with different activation and inactivation rates and sensitivities to calcium. We determined that there were optimal values for sensor parameters, but they were broadly tuned around these values and were independent from each other. Taken together, our results suggest that activity sensing for homeostatic regulation of the pyloric network can potentially be achieved with relatively few, simple calcium sensors and that the properties of these sensors need not necessarily be adjusted to the particular role of each neuron in the network. This work is supported by 1 R01 NS054911-01A1 from NINDS.Liu Z, Golowasch J, Marder E and Abbott LF. J. Neurosci.1998, 18(7):2309-2320