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.
Subject(s)
Electric Stimulation/methods , Glossopharyngeal Nerve/radiation effects , Neurons/physiology , Solitary Nucleus/cytology , Action Potentials/physiology , Action Potentials/radiation effects , Analgesics, Non-Narcotic/pharmacology , Animals , Cell Count , Dose-Response Relationship, Radiation , Glossopharyngeal Nerve/physiology , Male , Quinine/pharmacology , Rats , Rats, Sprague-Dawley , Reaction Time/physiology , Reaction Time/radiation effects , Stimulation, Chemical , Sucrose/pharmacology , Sweetening Agents/pharmacology , Taste/drug effects , Taste/physiology , Time Factors , Tongue/drug effects , Tongue/innervationABSTRACT
Rhenium-186 (tin) hydroxyethylidene diphosphonate (186Re-HEDP), a bone-seeking radiopharmaceutical, has been successfully used in the treatment of patients with painful bone metastases. Toxicity is usually limited to reversible thrombocytopenia. An infrequent but clinically significant side effect is the occurrence of transient cranial neuropathy. We report on two prostatic cancer patients with metastatic bone cancer. Both patients developed transient cranial neuropathy shortly after treatment with 186Re-HEDP. Transient neuropathy of cranial nerves needs to be distinguished from neurological abnormalities caused by disease progression.
