# Phosphorylation of Pyruvate Dehydrogenase as a Marker of Neuronal Inactivity in the Enteric Nervous System

## TL;DR

This study shows that phosphorylated pyruvate dehydrogenase (pPDH) can be used to detect inactive neurons in the gut's nervous system, similar to how it's used in the brain.

## Contribution

The study introduces pPDH as a novel marker for neuronal inactivation in the enteric nervous system.

## Key findings

- TTX treatment increased pPDH levels, indicating neuronal inactivation.
- Veratridine reduced pPDH levels, showing its sensitivity to neuronal activity.
- pPDH and pERK provide complementary measures of neuronal inactivation and activation in the ENS.

## Abstract

The enteric nervous system (ENS) regulates essential gut functions through interactions between neurons and glial cells. While tools for studying neuronal activation are well‐established, methods for tracking neuronal inactivation remain underdeveloped. Phosphorylated pyruvate dehydrogenase (pPDH) has emerged as a marker of neuronal inactivity in the brain. This study investigates whether pPDH can similarly serve as a reliable marker of neuronal inactivity in the ENS.

Whole‐mount preparations of the colonic myenteric plexus from mice were treated with veratridine (neuronal activator) or tetrodotoxin (neuronal inhibitor). Immunohistochemistry was used to label neurons with HuC/D and quantify pPDH (inactivity marker) and pERK (activation marker) labelling. Fluorescent signals were analyzed to assess changes in marker expression under different conditions.

TTX treatment increased pPDH labelling, as evidenced by higher fluorescence intensity and a greater percentage of pPDH‐positive neurons. In contrast, veratridine reduced pPDH levels, indicating its sensitivity to neuronal activity changes. Together, pPDH and pERK provide reliable measures of neuronal inactivation and activation, respectively, in the ENS.

This study establishes pPDH as a robust marker for neuronal inactivation in the ENS, complementing existing activation markers like pERK. These findings provide a novel framework for exploring neuron–glia communication and neuronal dynamics in the gut.

Phosphorylated pyruvate dehydrogenase (pPDH) serves as a novel histological marker of neuronal inactivation in the enteric nervous system. Pharmacological modulation of neuronal activity using TTX and veratridine revealed that pPDH levels are inversely correlated with neuronal firing. In contrast, pERK expression followed the opposite trend, validating the activity dependence of pPDH.