Measurement of intact quantal packet of transmitters released from single nerve terminal by loose-patch amperometry

Single-Vesicle Electrochemistry in Fresh Brain Slices Enables In Situ Quantification of Vesicular Monoamine

The quantitative analysis of vesicular neurotransmitters in neurons in situ is paramount for investigating neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease (PD). Unfortunately, a direct approach for monitoring neurotransmitter chemistry in single vesicles in fresh brain tissue has remained inaccessible so far. Here, we introduce an innovative platform of single-vesicle electrochemistry (SVE) in fresh brain tissue, enabling the quantification of neurotransmitters at the single-vesicle level for both soma and varicosity. Utilizing this methodology, we investigated a PD animal model, which demonstrated a significant reduction in both vesicular dopamine (DA) storage and exocytotic release in DA neurons in the substantia nigra. Furthermore, SVE unveiled the heterogeneous nature of chemical neurotransmission among DA neurons across different brain regions. Importantly, this tissue-based SVE approach can be extended to quantify other monoamine neurotransmitters, such as norepinephrine and serotonin, at the single-vesicle level. The introduction of this methodology marks a significant advancement, offering a novel avenue to explore neurological and psychiatric disorders through the lens of neurotransmitter signaling in the mammalian brain. This breakthrough has the potential to deepen our understanding of the underlying mechanisms of these complex disorders and may pave the way for the development of targeted therapeutic interventions.

Multi-Spatiotemporal Probing of Neurochemical Events by Advanced Electrochemical Sensing Methods

Neurochemical events involving biosignals of different time and space dimensionalities constitute the complex basis of neurological functions and diseases. In view of this fact, electrochemical measurements enabling real-time quantification of neurochemicals at multiple levels of spatiotemporal resolution can provide informative clues to decode the molecular networks bridging vesicles and brains. This Minireview focuses on how scientific questions regarding the properties of single vesicles, neurotransmitter release kinetics, interstitial neurochemical dynamics, and multisignal interconnections in vivo have driven the design of electrochemical nano/microsensors, sensing interface engineering, and signal/data processing. An outlook for the future frontline in this realm will also be provided.

Intestinal microbiota modulates adrenomedullary response through Nod1 sensing in chromaffin cells

The intestinal microbiota closely interacts with the neuroendocrine system and exerts profound effects on host physiology. Here, we report that nucleotide-binding oligomerization domain 1 (Nod1) ligand derived from intestinal bacteria modulates catecholamine storage and secretion in mouse adrenal chromaffin cells. The cytosolic peptidoglycan receptor Nod1 is involved in chromogranin A (Chga) retention in dense core granules (DCGs) in chromaffin cells. Mechanistically, upon recognizing its ligand, Nod1 localizes to DCGs, and recruits Rab2a, which is critical for Chga and epinephrine retention in DCGs. Depletion of Nod1 ligand or deficiency of Nod1 leads to a profound defect in epinephrine storage in chromaffin cells and subsequently less secretion upon stimulation. The intestine-adrenal medulla cross talk bridged by Nod1 ligand modulates adrenal medullary responses during the immobilization-induced stress response in mice. Thus, our study uncovers a mechanism by which intestinal microbes modulate epinephrine secretion in response to stress, which may provide further understanding of the gut-brain axis.