Osmotic Forces and Gap Junctions in Spreading Depression: A Computational Model

In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K⁺ is allowed to move through gap junctions. SD waves of K⁺]_out 25 to 60 mM moving at 2 to 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na⁺ currents are predicted to facilitate SD, while SK and A-type K⁺ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.