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Effects of electrical stimulation of the glossopharyngeal nerve on cells in the nucleus of the solitary tract of the rat

Elsevier B.V.
Publication Date
DOI: 10.1016/j.brainres.2006.07.029
  • Glossopharyngeal Nerve
  • Nucleus Of The Solitary Tract
  • Electrophysiology
  • Biology


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.

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