Thermodynamics of Neurotransmission

Abstract

There is a body of research mainly dedicated to study the means of temperature regulation in biological systems especially human body and how from small scale cells to to whole organ respond to temperature changes in the environment. This appropriate responses guarantee the maintenance of the condition under which, that biological system can function properly. Neural cells are no exception and their response perhaps requires a more precise measure because of their importance in a biological system. All of that being said, the mechanisms by which neurons produce, use and propagate heat are not studied. The main topic of thesis is dedicated to study those mechanisms, specifically the dynamics of temperature within the synaptic cleft. The transmission of neurotransmitters following release from pre-synaptic vesicles inside the synaptic cleft has been considered to be a diffusion process and its dynamics governed by Fick’s laws. But other existing forces might contribute to propagation of neurotransmit- ters such as the electric fields of narrow synaptic clefts and temperature gradients. Since the experimental methods to observe the processes inside synaptic cleft is limited, we mainly rely on theoretical methods arising from statistical physics, thermodynamics and fluid dynamics to study these processes. We use a non-equilibrium thermodynamic model which leads to system of partial differen- tial equations that describes dynamics of temperature inside synaptic cleft. Finite element method (FEM) simulations, suggest that linear relationship between temperature changes and other factors such as number of release from binding sites also temperature difference between intracellular vesicles and extracellular synaptic cleft parts. The findings can provide a basis for temperature changes that are independent from those induced by blood flow and provide further factors to temperature change during short-term synaptic plasticity, long term potentiation or pathological conditions such as Epilepsy.