Portal de Periódicos da CAPES

INTRODUCTION

1996; Oxford University Press; Volume: 21; Issue: 3 Linguagem: Inglês

10.1093/chemse/21.3.351

1464-3553

Robert M. Bradley,

Biochemical Analysis and Sensing Techniques

A complex chain of neural events is initiated when a chemical is placed on the tongue that eventually leads to a taste sensation. Beginning with transduction and a receptor potential, the sensory information has to be transformed into action potentials that ascend from the periphery through the central nervous system. This process involves many synaptic junctions where the message is transformed and distributed to a number of different brain areas. While transduction has been a major focus of recent investigations in taste, synaptic processing, and the neurotransmitters and neuromodulators used by the taste system have received less attention. Obviously, an understanding of the role of neurotransmitters and neuromodulators in the gustatory system is very important if progress is to be made in comprehending how taste information is processed by the central nervous system. Thus, it is timely to examine the current knowledge of the role of neurotransmitters and neuromodulators in gustation. A symposium at the Association for Chemoreception Sciences Annual Meeting (AChemS XVII) recently focused on this topic to address the role of neurotransmitters and neuromodulators at the level of the taste bud and at the first central relay in the taste pathway—the nucleus of the solitary tract (NST). The first report of this symposium is a comprehensive review by Steve Roper of the neurotransmitters and neuromodulators at the level of the taste receptors. Once transduction has taken place at the taste cell receptor membrane the information has to pass through a synapse between the taste cells and the primary afferent taste fibers. Suprisingly little is known about this essential event or about the identity of the neurotransmirter/s involved. As detailed in this report several investigators have attempted to study synaptic transmission at the taste bud. Histochemical, immunocytochemical and physiological techniques have been used in a number of different species with many conflicting results. Often an investigator produces a flurry of papers and then apparently abandons the effort. A few years later another investigator tries again, probably because new methods become available, to re-investigate the question of synaptic transmission at the level of the taste bud. Roper describes recent work from his laboratory indicating the significant role played by serotonin as a neuromodulator in the taste bud, but also reports that the identity of the neurotransmitter released at the taste cellprimary afferent fiber synapse is still unknown. In the last three reports information is presented on neurotransmiters and neuromodulators at the level of the NST. Synaptic events at the first relay in the central taste pathway are also little understood, as are the neurotransmiters