Afferent and Efferent Interactions in Taste

Bradley, Robert

Abstract

At least 80% of all lingual taste buds are located in foliate and circumvallate papillae on the posterior tongue of mammals, and these taste buds are exposed constantly to secretions of the von Ebner, lingual salivary glands. The von Ebner glands thus provide the fluid microenvironment for most tongue taste buds and the glands appropriately occupy a substantial mass of the posterior mammalian tongue. Past work in the laboratory has described the neural control of von Ebner salivary glands and demonstrated interactions between the taste system and the von Ebner salivary gland system. Proposed experiments now are focused on investigations to gain a detailed understanding of the brainstem neural controls and interactions linking gustatory and von Ebner gland systems. It is well established that secretions of the von Ebner glands are regulated by parasympathetic, secretomotor neurons located in the inferior salivatory nucleus in the brain-stem. However, virtually nothing is known about the morphology of, or afferent projections to, these particular secretomotor neurons. Because of the close proximity of neurons in this nucleus to second order taste neurons in the nucleus of the solitary tract (NTS), and because of our past work on taste-von Ebner gland interactions, it is proposed that NTS cells provide some afferent input to cells in the inferior salivatory nucleus. An in vitro brain slice preparation and in vivo neuron labelling procedures will be used to determine the detailed neurophysiological and morphological characteristics of neurons in the inferior salivatory nucleus, and the afferent projections to these cells. Intracellular recording, and neuron reconstruction methods will be used. In addition, the brain slice preparation will be used to characterize the detailed neurophysiological and morphological characteristics of NTS neurons that are associated with the parasympathetic secretomotor neurons. Data from experiments in this proposal will provide basic new information on the neurobiology of secretomotor neurons that control salivary glands, of taste neurons and of interactions between taste-salivary neural systems in the brain-stem. This basic information will contribute to understanding specific clinical problem related to reduced salivary secretion.