Simulations of amperometric monitoring of exocytosis: moderate pH variations within the cell-electrode cleft with the buffer diffusion

Amperometry with ultramicroelectrodes is nowadays a routine technique to investigate neurotransmitter secretion by vesicular exocytosis at the single-cell level. This electroanalytical tool allows one to understand many aspects of the vesicular release in terms of mechanisms. However, the electrochemical detection relies on the oxidation of released neurotransmitters that produce 2H(+) and thus the possible acidification of the cell-electrode cleft. In a previous work, we considered a model involving the H+ diffusion or/and its reaction with buffer species. In this article, we report a more general model which takes into account the ability of buffer species to move and to be regenerated within the cell-electrode cleft. As a consequence, the pH within the cleft is still equal to its physiological value regardless of the electrochemical detection of the vesicular release for usual exocytotic cell frequencies. This confirms that amperometry at the single-cell level is a very robust technique for investigating vesicular exocytosis.

Automated summary

Amperometry with ultramicroelectrodes is a routine technique for investigating neurotransmitter secretion by vesicular exocytosis at the single-cell level. The electrochemical detection may lead to acidification of the cell-electrode cleft, but a more general model taking into account buffer species movement and regeneration confirms the robustness of this technique. This model ensures that the pH within the cleft remains at its physiological value during usual exocytotic cell frequencies, regardless of the electrochemical detection of vesicular release.