The vago-vagal reflex is a neural circuit of the tenth cranial nerve involved in the homeostatic regulation of various respiratory and gastrointestinal functions. However, its contribution to blood glucose regulation is not yet fully understood. Focusing on the sensory modality of the vago-vagal loop, we hypothesize that pancreatic sensory neurons detect and communicate information about the pancreatic islet's microenvironment to the nucleus of the solitary tract (NTS). We pursued this hypothesis by labeling activated neurons in the NTS in response to β-cell-specific stimulation. We injected mice with an adeno-associated virus containing an insulin promoter that drove the expression of a designer receptor, DREADD, activated by a designer drug, CNO, in β-cells. After administering CNO, we labeled neurons in the brain for cFos, a marker of neuronal activation. cFos staining proved to be an accurate method for detecting neuronal activation in the brain in response to strong intraperitoneal stimulation. However, cFos is not a sensitive reporter for weak and indirect neuronal activation. Despite a tendency for a higher number of cFos positive nuclei in DREADD-mice injected with CNO, this difference was not statistically significant. For proper analysis, we must increase the sample size and introduce stricter control conditions.
