Afferent and Efferent Interactions in Taste

Bradley, Robert

Abstract

The long-term goal of this laboratory is to understand the sensory input and brainstem neural circuits involved in processing taste information. Based on results obtained in the prior grant period, there is a much greater understanding of the mechanisms involved in neural processing in the rostral nucleus of the solitary tract (rNST). In the proposed grant, properties of afferent gustatory neurons, neurons in rNST, and neurons in the pontine taste relay, the parabrachial nucleus (PBN), will be examined. In addition effects of neuromodulators, known to influence feeding behavior, on the synaptic activity of rNST neurons will be studied. Specifically, whole cell recordings of neurons in in vitro brain slice preparations and acutely dissociated neurons will be used to study: 1. The biophysical characteristics of primary afferent neurons involved in conveying taste information to the brainstem. 2. The mechanisms of inhibition in rNST by investigating the biophysical characteristics of rNST interneurons. 3. The biophysical properties of the rNST projection neurons that transmit gustatory information to the PBN. 4. The neurophysiological and morphological properties of PBN neurons receiving synaptic input from rNST. 5. The effects of neuromodulators known to influence feeding behavior on synaptic activity of rNST neurons. Since the sense of taste has a primary role in feeding, in regulating food and fluid intake, and in the initiation of oral reflex activity such as salivary secretion, it is important to learn how sensory information originating in taste receptors is processed and distributed by taste relay nuclei. It is also important to understand the mechanisms of action of neurochemicals that influence feeding at the taste relay nuclei. The experiments detailed in this proposal will provide important new information on the neural circuits, neurotransmitters and neuromodulators responsible for integrating, modifying and distributing the information that originates in taste receptors, and will thereby provide greater understanding of the role of the gustatory system in feeding and feeding-related disorders.