Role Played by Afferent Signals from Olfactory, Gustatory and Gastrointestinal Sensors in Regulation of Autonomic Nerve Activity

Abstract

Afferent signals from the olfactory system, gustatory system and gastrointestinal (GI) tract control visceral functions such as oral and gut secretions and several digestive, endocrine, thermogenic, cardiovascular and renal responses via autonomic reflexes. It is well known that odors and tastes, such as umami, can stimulate oral and GI secretions to improve food intake and digestion in a process termed the cephalic phase response. The perception of GI nutrients, such as carbohydrates and amino acids, can control food digestion, absorption and utilization via the vago-vagal reflex during a meal. Recent advances in understanding the molecular physiology of taste indicate that taste receptors able to sense such nutrients are widely distributed in the GI tract, including the oral cavity. These receptors act as nutrient sensors to trigger food digestion, the release of GI peptides and the formation of food preferences. In this paper, we review recent evidence on the regulation of GI functions by the autonomic nervous system via peripheral odor and nutrient sensors.