title: Response latency to lingual taste stimulation distinguishes neuron types within the geniculate ganglion.
abstract: The purpose of this study was to investigate the role of response latency in discrimination of chemical stimuli by geniculate ganglion neurons in the rat. Accordingly, we recorded single-cell 5-s responses from geniculate ganglion neurons (n = 47) simultaneously with stimulus-evoked summated potentials (electrogustogram; EGG) from the anterior tongue to signal when the stimulus contacted the lingual epithelium. Artificial saliva served as the rinse solution and solvent for all stimuli [(0.5 M sucrose, 0.03-0.5 M NaCl, 0.01 M citric acid, and 0.02 M quinine hydrochloride (QHCl)], 0.1 M KCl as well as for 0.1 M NaCl +1 μM benzamil. Cluster analysis separated neurons into four groups (sucrose specialists, NaCl specialists, NaCl/QHCl generalists and acid generalists). Artificial saliva elevated spontaneous firing rate and response frequency of all neurons. As a rule, geniculate ganglion neurons responded with the highest frequency and shortest latency to their best stimulus with acid generalist the only exception. For specialist neurons and NaCl/QHCl generalists, the average response latency to the best stimulus was two to four times shorter than the latency to secondary stimuli. For NaCl-specialist neurons, response frequency increased and response latency decreased systematically with increasing NaCl concentration; benzamil significantly decreased NaCl response frequency and increased response latency. Acid-generalist neurons had the highest spontaneous firing rate and were the only group that responded consistently to citric acid and KCl. For many acid generalists, a citric-acid-evoked inhibition preceded robust excitation. We conclude that response latency may be an informative coding signal for peripheral chemosensory neurons.
authors.affiliation: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL 32306-4301, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Breza
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Nikonov
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Contreras
mesh_terms: D000818:Animals; D019343:Citric Acid / Q000494:pharmacology; D005830:Geniculate Ganglion / Q000166:cytology / Q000502:physiology*; D008036:Lingual Nerve / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D011189:Potassium Chloride / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000145:classification / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D013268:Stimulation, Chemical; D013395:Sucrose / Q000494:pharmacology; D013649:Taste / Q000187:drug effects / Q000502:physiology*
chemical_list: D019343:Citric Acid; D012965:Sodium Chloride; D013395:Sucrose; D011189:Potassium Chloride; D011803:Quinine