ABSTRACT
In this review, the authors present an hypothesis which brings all these diverse functions of vagal afferents, particularly those from the gut, together into one coherent scheme. They argues that the unifying concept underlying these diverse functions is that vagal afferents constitute the major intero-protective system for the body. The vomiting reflex also provides a good example of such interactions between systems, between components and of visceral events since emetic activation of the abdominal vagal afferents produces reflex changes in the cardiovascular, respiratory and gastrointestinal systems and in addition may alter secretion of pituitary hormones. This chapter considers only the possibility of vagal afferents initiating the conscious se sensations and does not discuss the central generation of such sensations nor their "referral" to the gut. It focuses on visceral afferents as the origin of the sensation, the focus is not meant to exclude an involvement of central sites such as the area postrema. Stimulation of the abdominal visceral afferents produces a characteristic apnoeic response followed by depression of diaphragmatic activity.
