The pontine parabrachial nucleus (PbN) serves as the second central relay in the gustatory pathway and is a critical site for the integration of taste and visceral information. The medullary dorsal motor nucleus of the vagus (DMV) is a key component of vago-vagal reflex circuits, and anatomical evidence suggests that DMV neurons project directly to the PbN. However, it remains unclear whether the DMV exerts a functional influence on taste-responsive PbN neurons. In the present study, we investigated this question by recording extracellular single-unit activity from gustatory PbN neurons in urethane-anesthetized hamsters. Taste responsiveness was established by applying sucrose, NaCl, citric acid, and quinine hydrochloride to the anterior tongue. Seventy-five of 80 responsive neurons (93.8%) were orthodromically excited by ipsilateral DMV stimulation. In addition, contralateral DMV stimulation activated 39 neurons (48.8%), of which 32 were excited and 7 were inhibited. No antidromic responses were observed, suggesting that a reciprocal PbN-to-DMV projection was weak or absent among the neurons examined. The effect of DMV activation on taste-evoked responses was examined in 20 PbN neurons that were excited and 7 that were inhibited by DMV stimulation. DMV train stimulation enhanced taste responses in all 20 excited neurons and suppressed taste responses in all 7 inhibited neurons without altering the preferred taste stimulus. These results demonstrate that gustatory PbN neurons receive convergent inputs from the DMV and that DMV activation bidirectionally modulates pontine taste processing, providing a potential neural substrate through which visceral signals influence gustatory responses.

Introduction
Materials and Methods
    1. Animal surgery
    2. Single-unit recording and taste stimulation
    3. Electrical stimulation of the dorsal motor nucleus ofthe vagus
    4. Histology
    5. Data analysis
Results
    1. Histology
    2. Taste response characteristics of parabrachialnucleus neurons
    3. Orthodromic responses of parabrachial nucleustaste neurons to dorsal motor nucleus of the vagusstimulation
Discussion
    1. Convergence of gustatory and visceral input in theparabrachial nucleus
    2. Response characteristics: ipsilateral dominance andcontralateral inhibition
    3. Dorsal motor nucleus of the vagus activationmodulates taste responses of parabrachial nucleusneurons
    4. Physiological implications
Funding
Conflicts of Interest
References

• Cheng-Shu Li(Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, United States)
• Young Kyung Cho(Department of Physiology and Neuroscience, College of Dentistry, Kangwon National University, Gangneung 25457, Republic of Korea, Research Institute of Oral Sciences, Kangwon National University, Gangneung 25457, Republic of Korea) Corresponding author
• Ki-Myung Chung(Department of Physiology and Neuroscience, College of Dentistry, Kangwon National University, Gangneung 25457, Republic of Korea, Research Institute of Oral Sciences, Kangwon National University, Gangneung 25457, Republic of Korea)
• Kyung-Nyun Kim(Department of Physiology and Neuroscience, College of Dentistry, Kangwon National University, Gangneung 25457, Republic of Korea, Research Institute of Oral Sciences, Kangwon National University, Gangneung 25457, Republic of Korea)