Gustatory Connectivity and Central Projections of the Mouse Petrosal-Nodose-Jugular Ganglia Complex

The petrosal, nodose, and jugular ganglia (PNJ) complex is a major sensory gateway through which gustatory, visceral, and somatosensory information from the body is transmitted to the brain. Despite its importance, experimental access to the PNJ complex in mice remains technically challenging, limiting strategies for anatomical tracing and functional manipulation of these pseudounipolar neurons. Here, we detail an improved surgical approach for direct viral vector delivery to the mouse PNJ complex and demonstrate utility of the technique by labeling peripheral and brain-wide central projections from the PNJ. Focusing on the gustatory system, we report viral expression of fluorescent reporters to label gustatory fibers innervating taste tissues at three levels of selectivity: broad labeling of tongue-innervating afferents, genetic targeting of gustatory neurons using P2X2-Cre mice, and selective labeling of sour-responsive neurons using Penk-Cre mice. In the brainstem, the PNJ gustatory neurons terminate at the rostral nucleus of the solitary tract. In addition, we observed PNJ-derived neuron projections to diverse brain regions, including the cervical spinal cord, area postrema, lateral reticular nucleus, nucleus ambiguus, and spinal trigeminal tract. Together, this work provides a practical platform for selectively labeling, isolating, or manipulating PNJ neurons in mice of either sex, enabling future studies of the anatomical organization and functional roles of diverse body-to-brain sensory pathways. Significance Statement The petrosal–nodose–jugular (PNJ) ganglion complex, located in the upper neck, contains sensory neurons that provide critical connections between internal organs and the brain. In this study, we describe an optimized surgical method for directly accessing the PNJ complex and demonstrate its utility by microinjecting viral vectors encoding fluorescent reporters to map sensory neural circuits. As a proof of concept, this approach delineated the tongue-to-brainstem pathway that conveys taste information.