Emergent dynamics in an astrocyte-neuronal network coupled via nitric oxide

TL;DR

This study models an astrocyte-neuronal network coupled via nitric oxide, revealing emergent calcium wave dynamics and synchronization phenomena that may enhance synaptic efficiency.

Contribution

It introduces a minimal coupled network model of astrocyte-neuron units mediated by nitric oxide, demonstrating emergent calcium wave behaviors and synchronization regimes.

Findings

Multiple stable dynamical regimes in astrocytes.

Existence of a coupling range inducing synchronization.

Stimulus-dependent calcium wave propagation.

Abstract

In the brain, both neurons and glial cells work in conjunction with each other during information processing. Stimulation of neurons can cause calcium oscillations in astrocytes which in turn can affect neuronal calcium dynamics. The "glissandi" effect is one such phenomenon, associated with a decrease in infraslow fluctuations, in which synchronized calcium oscillations propagate as a wave in hundreds of astrocytes. Nitric oxide molecules released from the astrocytes contribute to synaptic functions on the basis of the underlying astrocyte-neuron interaction network. In this study, by defining an astrocyte-neuronal (A-N) unit as an integrated circuit of one neuron and one astrocyte, we developed a minimal model of neuronal stimulus-dependent and nitric oxide-mediated emergence of calcium waves in astrocytes. Incorporating inter-unit communication via nitric oxide molecules, a coupled network of 1,000 such A-N units is developed in which multiple stable regimes were found to emerge in astrocytes. We examined the ranges of neuronal stimulus strength and the coupling strength between A-N units that give rise to such dynamical behaviors. We also report that there exists a range of coupling strength, wherein units not receiving stimulus also start showing oscillations and become synchronized. Our results support the hypothesis that glissandi-like phenomena exhibiting synchronized calcium oscillations in astrocytes help in efficient synaptic transmission by reducing the energy demand of the process.