title: Effects of electrical stimulation of the glossopharyngeal nerve on cells in the nucleus of the solitary tract of the rat.
abstract: Electrophysiological responses to electrical stimulation of the lingual branch of the glossopharyngeal (GP) nerve (which innervates taste buds on the caudal 1/3 of the tongue) were recorded from single cells in the rostral nucleus of the solitary tract (NTS) of anesthetized rats. Electrical stimulation was delivered as single pulses (n=55), paired-pulses (n=15) and tetanic trains (n=11). NTS cells with GP-evoked responses were also tested for responsivity to taste stimuli (0.1 M NaCl, 0.5 M sucrose, 0.01 M HCl and 0.01 M quinine HCl). Fifty-five neurons were studied: 49 cells showed GP-evoked (mean latency+/-SEM=18.0+/-1.32 ms); seven of these were taste-responsive. Spontaneous rate of these cells was low (mean+/-SEM=1.4+/-0.3 spikes per second; median=0.21 spikes per second) and many cells showed no spontaneous activity. Paired-pulse stimulation of the GP nerve in 13 rats produced both paired-pulse suppression (n=11) and paired-pulse enhancement (n=4); tetanic stimulation (25 Hz, 1.0 s) produced sustained (>20 s) increases or decreases in firing rate in 7 of 11 cells tested. Histological data suggested that GP-evoked responses recorded in the most rostral NTS were likely the result of polysynaptic connections. Cells with GP-evoked responses formed a heterogeneous group in terms of their response properties and differed from cells with evoked responses to chorda tympani (CT; which innervates taste buds on the rostral 1/3 of the tongue) nerve stimulation. These differences may reflect the respective functional specializations of the GP and CT nerves.
authors.affiliation: Department of Psychology, Box 6000, State University of New York at Binghamton, Binghamton, New York 13902-6000, USA. rob.hallock@UCHSC.edu
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hallock
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Di Lorenzo
mesh_terms: D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000818:Animals; D002452:Cell Count; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods*; D005930:Glossopharyngeal Nerve / Q000502:physiology / Q000528:radiation effects*; D008297:Male; D009474:Neurons / Q000502:physiology*; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D017552:Solitary Nucleus / Q000166:cytology*; D013268:Stimulation, Chemical; D013395:Sucrose / Q000494:pharmacology; D013549:Sweetening Agents / Q000494:pharmacology; D013649:Taste / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014059:Tongue / Q000187:drug effects / Q000294:innervation
chemical_list: D018712:Analgesics, Non-Narcotic; D013549:Sweetening Agents; D013395:Sucrose; D011803:Quinine