Effects of time-dependent ATP consumption caused by neuron firing on ATP concentrations in synaptic boutons containing and lacking a stationary mitochondrion

The reason why only about half of the presynaptic release sites lack a stationary mitochondrion, and how the sites without a stationary mitochondrion are supplied with ATP, is still not fully understood. This paper develops a mathematical model designed to simulate the transient ATP concentration in presynaptic en passant boutons. The model is utilized to investigate how the ATP concentration responds to increased ATP demand during neuronal firing in boutons with a stationary mitochondrion and those without one. The analysis suggests that neuron firing may cause oscillations in the ATP concentrations, with peak-to-peak amplitudes ranging from 0.4% to 5% of their average values. However, this does not deplete boutons lacking a mitochondrion of ATP; their concentration remains approximately 3.75 times higher than the minimum concentration required for synaptic activity. The variance in average ATP concentrations between boutons containing a stationary mitochondrion and those lacking one ranges from 0.3% to 0.8%, contingent on the distance between the boutons. The model indicates that diffusion-driven ATP transport is rapid enough to adequately supply ATP molecules to boutons lacking a stationary mitochondrion.