Obesity has become a worldwide disease, posing a rapidly increasing challenge to the global healthcare system. The primary reason for obesity is that food intake exceeds the body’s needs. The central nervous system monitors the body’s energy status by continuously receiving peripheral gut-derived signals and functions as a master regulator in controlling feeding behaviors. Vagal afferents transmit gut-derived consumption signals from the periphery to the hindbrain (e.g., the nucleus of the solitary tract (NTS)). In contrast, vagal efferent nerves send commands to regulate peripheral organ activities. However, the precise role of the gut–vagus–NTS pathway and the gut–brain axis in regulating food intake is not yet fully understood. This review highlights the key roles of the NTS, vagal sensory neurons, and the gastrointestinal system in regulating feeding behaviors.

Ganglia are nodular structures in the peripheral nervous system (PNS) that are formed by a cluster of neuron somas. They have important roles in communicating signals from peripheral organs to the nervous system and work as a unique structure of the PNS. As great advances in neuronal manipulation and recording techniques have been made, an increasing amount of research is focused on the function of ganglia. However, ganglion surgery is still very challenging, particularly in small animals such as mice. In the present study, we performed anatomical analyses of two types of sensory ganglia, the dorsal root ganglia and the trigeminal ganglia. Hematoxylin and eosin (H&E) staining revealed structural differences between ganglia and nerve fibers. Immunofluorescence staining with antibodies to neuronal nuclear antigen (NeuN), a neuron-specific marker, labels neurons in ganglia and distinguishes ganglia from other tissues, such as lymph nodes. This study describes the anatomical analysis of the dorsal root ganglia and the trigeminal ganglia, which provides an anatomical basis for functional studies.