The proposed study is designed to identify and characterize neuronal mechanisms in the brainstem which are concerned with gastric function. We are especially interested in the response of central neuronal mechanisms in the brainstem, which receive afferent input from the stomach, in terms of 1) neuronal interactions and distributions on single neurons and 2) the neurotransmitters involved. Gastric branches of the vagus and splanchnic nerves will be electrically stimulated, in anesthetized cats, while recording extracellularly from neurons in nucleus tractus solitarius (NTS) and area postrema in the caudal, dorsomedial area of the brainstem. The study will focus on temporal and spatial relationships of the ventral and dorsal gastric vagal input on these neurons. Electrical stimulation of gastric nerves; distention of the stomach, and local gastric intra- arterial injection of substance will used to activate sensory receptors of nerve fibers which send information to the brainstem. Substances will be locally applied by micropressure on neurons in the brainstem activated by these stimuli to investigate putative neurotransmitters involved in synaptic transactions between the stomach and brain. The role of greater splanchnic nerve and its contribution to brainstem interactions involved in regulation of gastric responses will be studied. The results of these studies will extend our knowledge of 1) brainstem mechanisms which receive sensory information from the corpus and antrum of the stomach and 2) and the distribution and response of neurons in NTS and area postrema which receive gastric input. The new and exciting data which gave rise to the studies in this proposal and the potential results will provide the basis for more informed decisions into diagnosis and treatment of digestive problems, including eating disorders such as obesity, anorexia and management of bulimia.
