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PubMed1994

The responses to choline ions induced by transition metal ions in single water fibers of the frog glossopharyngeal nerve.

In single water-sensitive fibers (water fibers) of the frog glossopharyngeal nerve, application of a solution of 500 mM choline C1 to the tongue elicited responses of varying magnitude. Some water fibers (plain choline-insensitive water fibers) barely responded to the solution, while some water fibers (plain choline-sensitive water fibers) exhibited a considerable response to this solution. NiCl2, which is barely effective in producing neural response at concentrations below 5 mM, induced the response of plain choline-insensitive water fibers to choline+ ions. It was confirmed, in a collision test, that the Ni(2+)-induced responses to choline+ ions were derived from water fibers. However, NiCl2 did not affect the magnitude of the response generated by choline+ ions in plain choline-sensitive water fibers. The concentration-response curve for choline C1 in the presence of 1 mM NiCl2 for plain choline-insensitive water fibers was similar to the curves obtained in the absence of NiCl2 for plain choline-sensitive water fibers. Other organic salts, such as tris(hydroxymethyl)aminomethane-HCl, triethanolamine-HCl and tetraethylammonium C1, elicited no response or only a very small response from water fibers, and NiCl2 did not affect these responses. It is suggested that there exists a choline receptor for the response to choline+ ions in the apical membrane of frog taste cells and that Ni2+ ions expose the sites of such choline receptors, which are deeply embedded in the receptor membrane, to the outside medium. The effect of Ni2+ ions results in an increase in the number of the choline receptor sites available for binding of choline+ ions. The rank order of effectiveness of transition metal ions in eliciting the appearance or enhancement of the response to choline C1 was Ni2+ > Co2+ > Mn2+. Mg2+ ions had no effect on the response to choline+ ions. A similar rank order was previously obtained in enhancement of the responses to Ca2+, Mg2+ and Na+ ions (Kitada, 1994a). It seems likely that the mechanism for enhancement or elicitation of the response to choline+ ions by the transition metal ions has features in common with that for enhancement of the responses to Ca2+, Mg2+ and Na+ ions.

Animals↗
PubMed2003

Hiccup reflex is mediated by pharyngeal branch of glossopharyngeal nerve in cats.

Hiccup reflex is a coordinated motor activity that causes a brief strong inspiratory movement accompanied by glottic adduction. Our previous study has demonstrated that mechanical stimulation of the dorsal epipharynx elicits hiccup-like response. To identify the afferent pathway of the hiccup-like response, the pharyngeal branch of the glossopharyngeal nerve (PB-GPN) which distributed to the dorsal epipharyngeal area was electrically stimulated in anesthetized, spontaneously breathing cats. To access the epipharynx and to directly observe a glottic movement, we made a submental opening at the region rostral to the epiglottis. An activity from the lateral cricoarytenoid (LCA) muscle of the larynx was recorded as an index of glottic adduction, and intrapleural pressure (Ppl) as an index of an inspiratory movement. Electrical stimulation of PB-GPN evoked a fixed motor pattern of hiccup-like response representing a spiky strong negative change in Ppl accompanied by an initial brief burst of LCA electromyogram (EMG). LCA excitation occurred prior to the spiky inspiratory movement. An initial and transient glottic adduction during the response was confirmed by direct observation. Electrical stimulation of the main trunk of the glossopharyngeal nerve evoked expiratory reflex, but not inspiratory (hiccup-like) response. These results indicated that PB-GPN is responsible for hiccup reflex.

Afferent Pathways↗
PubMed1985

Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon.

The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophageal resting pressure was observed relating to the electrical inhibitory component. Hexamethonium caused complete disappearance of any EMG response to glossopharyngeal stimulation, as well as suppression of mechanical responses. The comparison between the EMG responses to swallow and to efferent glossopharyngeal stimulation suggests that in pigeon cervical oesophagus: primary peristalsis is central in origin; a dual system of glossopharyngeal fibres, excitatory and inhibitory, carries the central control for oesophageal motility; these excitatory and inhibitory fibres supply the oesophageal muscle via intramural neurons; the synaptic arrangement of the inhibitory pathway is more complex than the excitatory one.

Animals↗
PubMed1983

Surface and intramedullary potentials evoked by stimulation of the glossopharyngeal nerve in frogs.

The bulbar potentials evoked by afferent volleys in the bullfrog glossopharyngeal nerve and in its 2 distal branches were studied. Following supramaximal electric stimulation of the peripheral nerve, the potential consisting of 2 triphasic deflections (S1 and S2) of presynaptic origin and 4 postsynaptic negative waves, N1, N2, N3 and N4, having the peak latency of 5, 8, 30 and 80 ms, respectively, was obtained along the nucleus fasciculus solitarius. By lowering the stimulus intensity to the threshold for exciting mechanosensitive fibers, only S1 followed by N1, N3 and N4 was produced, whereas, at higher intensities, S2 which accompanied by N2 became apparent. N1 and N2 waves were distributed over the bulbar dorsal surface with the maximal amplitude at 1-2 mm rostral to the obex and 0.5-1 mm lateral from the midline, the negativity being found maximal at the depth 0.5-1 mm from the surface. The surface-recorded N2 potential evoked by stimulation of the medial branch distributed caudal to that produced by stimulation of the lateral branch. Of intramedullary-recorded 4 negative waves, only N1 caused by volleys in the lateral branch distributed deeper layer than the one evoked by those in the other branch.

Afferent Pathways↗
PubMed2000

Glossopharyngeal nerve transection does not alter taste reactivity to sucrose conditioned to be aversive.

Glossopharyngeal nerve (GL) transection in rats is known to markedly reduce gaping, a stereotypical aversive oromotor behavior, in response to intraorally delivered quinine. In this experiment we tested whether GL transection would reduce gaping in response to an otherwise palatable stimulus (sucrose) but conditioned to be aversive. Sprague-Dawley rats were implanted with intraoral cannulae. Five received bilateral transection of the GL and five served as sham-operated controls. Water-deprived rats were presented with 0.3 M sucrose for 15 min immediately followed by an injection of 0.15 M LiCl on three occasions. Rats were then habituated to the taste reactivity chamber and intraoral fluid infusion for 3 days, and tested on day 4 with a 1 ml infusion (1 min) of 0.3 M sucrose. All rats drank negligible amounts of sucrose by the third conditioning session and there were no differences in sucrose intake between the groups. There were no significant differences in gapes, or any other measured oromotor response, to sucrose between GL-transected and sham-operated rats. These results show that the GL is not a necessary afferent limb for gaping in response to conditionally aversive taste compounds.

Animals↗
PubMed2002

Anatomy of the tonsillar bed: topographical relationship between the palatine tonsil and the lingual branch of the glossopharyngeal nerve.

Taste disturbance may result from injury to the lingual branch of the glossopharyngeal nerve (LBGN) during tonsillectomy. Because an understanding of the anatomy of this nerve is required in order to avoid injuring it, a gross, histologic anatomic study was undertaken of the topographical relationship between the LBGN and the muscle layer of the palatine tonsillar bed. Evaluation of 107 sides of 83 Japanese adult cadavers (aged 27-88 years) confirmed that the muscular composition and lamination of the tonsillar bed do not change with age or pathological conditions such as inflammation. In about a quarter (23.4%) of cases, the LBGN traveled inferior to the styloglossus muscle and lateral to the superior constrictor pharyngeal muscle over its whole course to the base of the tongue, so that the palatine tonsil was clearly separated from the LBGN. In 55.1% of cases, however, the muscle lining of the tonsillar bed was discontinuous and thin muscle bundles, derived from the stylopharyngeus, palatopharyngeus or superior constrictor pharyngeal muscle, partially covered the tonsillar capsule externally. Moreover, in 21.5% of cases the LBGN was firmly adherent to the tonsillar capsule, due to the complete absence of muscles lining the tonsillar bed. In these cases, and also probably in a similar percentage of patients undergoing tonsillectomy, taste disturbance may occur on removal of the hypertrophic tonsillar capsule. Therefore, minimal disturbance of the tonsillar bed is recommended in all cases of tonsillectomy.

Adult↗
PubMed1983

Developmental changes in taste responses from glossopharyngeal nerve in sheep and comparisons with chorda tympani responses.

To learn whether there are developmental changes in salt and acid taste responses from the posterior tongue, we recorded from the glossopharyngeal nerve, which innervates taste buds in circumvallate papillae, in sheep fetuses, lambs and adults. Multifiber responses to NH4Cl, KCl, NaCl, LiCl, citric and hydrochloric acids were expressed as ratios, relative to responses for two standard chemicals, NH4Cl and KCl. Response ratios for NaCl and LiCl, relative to either standard, increased during development, but the magnitude of the change was small. KCl elicited very large magnitude responses, relative to NH4Cl, in the youngest fetuses, and then decreased by 50% in stimulating effectiveness. Relative responses to both acids also decreased developmentally. The general shapes of KCl response-concentration functions did not change throughout development; however, in the youngest fetuses, the NH4Cl responses-concentration function was not similar to that in older animals. These developmental changes are different than those for responses from anterior tongue taste buds recorded from the chorda tympani nerve. Anterior tongue responses to NaCl and LiCl change most substantially and those to KCl change very little; acid responses do not change. The developmental differences for anterior versus posterior tongue responses suggest that membrane composition and maturational changes of taste buds in the two locations are not the same. Response-concentration functions from both tongue areas support the proposition that specific membrane components interacting with various salts are added during development.

Aging↗
PubMed1987

Brain stem projections of the glossopharyngeal nerve and its carotid sinus branch in the rat.

Transganglionic transport of horseradish peroxidase or lectin-conjugated horseradish peroxidase from an application site in the cervical trunk of the glossopharyngeal (IXth cranial) nerve of the rat produced extraperikaryal reaction product characteristic of axon terminal processes in three regions of the brain stem: (1) the nucleus of the tractus solitarius, from approximately 2.5 mm rostral to the obex to approximately 3 mm caudal to the obex; (2) the spinal trigeminal nucleus at the level of obex; (3) the cuneate fasciculus, approximately 3 mm caudal to the obex. In contrast, labelling of the carotid sinus nerve, a branch of the glossopharyngeal nerve which conveys chemoreceptor and baroreceptor afferent fibers from the carotid bifurcation, revealed a restricted central projection to within 1 mm of the obex and corresponding to the intermediate region of the glossopharyngeal nerve projection to the nucleus of the tractus solitarius. Two distinct aggregations of label were observed: (1) rostral to the obex, within the lateral and dorsomedial subnuclei of the nucleus of the tractus solitarius; (2) caudal to the obex, within the commissural and ventrolateral subnuclei of the nucleus of the tractus solitarius. Between these two sites the density of labelling was reduced. Retrogradely labelled neurons were demonstrated in the inferior salivatory nucleus and in the nucleus ambiguus after application of lectin-conjugated horseradish peroxidase to the glossopharyngeal nerve. Of the labelled neurons in the nucleus ambiguus (approximately 100), 25% contributed fibers to the carotid sinus nerve. The concentration of extraperikaryal reaction product located rostral to the obex after labelling of the carotid sinus nerve closely matches descriptions of the region of afferent terminations from carotid and aortic baroreceptors in the cat. The concentration of label caudal to the obex may therefore correspond to the region of afferent terminations from carotid chemoreceptors. This study may therefore provide some basis for a separation of the central synapses of primary afferent fibers from the carotid baroreceptors and chemoreceptors in the rat. The labelled neurons of the nucleus ambiguus provide the anatomical substrate for centrifugal control of carotid chemoreceptor activity.

Afferent Pathways↗
PubMed1992

Properties of the lingual and LVP branches of the glossopharyngeal nerve.

We investigated the effects of various stimuli on the afferent and efferent branches of the glossopharyngeal nerve in the rat soft palate. One of the sensory components, the lingual branch, responded to tactile stimulation, while the LVP branch responded to stretching of the levator veli palatini muscle. We also obtained physiological and morphological evidence of the existence of muscle spindles in the levator veli palatini muscle and showed that tactile stimulation of the contralateral soft palate and stretching of the contralateral LVP modulated discharges from the motor component of the ipsilateral levator veli palatini muscle. Our results suggest that these receptor units with both sensory and motor efferents may be the main determinants of modulation of respiratory movements in the upper airway by the IXth nerve.

Afferent Pathways↗
PubMed1986

Central connections of the lingual-tonsillar branch of the glossopharyngeal nerve and the superior laryngeal nerve in lamb.

Afferent and efferent central connections of the lingual-tonsillar branch of the glossopharyngeal nerve (LT-IX) and the superior laryngeal nerve (SLN) in the lamb were traced with horseradish peroxidase (HRP) histochemistry. After entering the brainstem, most LT-IX and SLN afferent fibers turned caudally in the solitary tract (ST). Some afferent fibers of LT-IX terminated in the medial nucleus of the solitary tract slightly caudal to their level of entry. The remaining fibers projected to the dorsolateral, ventrolateral, and interstitial areas of the nucleus of the solitary tract (NST) at the level of the area postrema. Superior laryngeal nerve afferent fibers terminated extensively in the medial and ventral NST at levels near the rostral pole of the area postrema. Further caudal, near the level of obex, SLN afferent terminations were concentrated in the region ventrolateral to the ST and in the interstitial NST. The caudal extent of LT-IX and the rostral extent of SLN terminals projected to similar levels of the NST, but only a relatively small proportion of the total projections overlapped. Lingual-tonsillar and SLN fibers also coursed rostrally to terminate in the caudal pons within and medial to the dorsomedial principal sensory trigeminal nucleus. Other labeled afferent fibers traveled caudally in the dorsal spinal trigeminal tract to terminate in the dorsal two-thirds of the spinal trigeminal nucleus at the level of obex. Large numbers of labeled cells with fibers in the LT-IX or SLN were located in the ipsilateral rostral nucleus ambiguus and surrounding reticular formation. Fewer labeled cells were observed in the inferior salivatory nucleus following HRP application to either the LT-IX or SLN. The LT-IX and SLN projections to areas of the NST associated with upper airway functions, like swallowing and respiration, suggest an important role for these two nerves in the initiation and control of airway reflexes.

Animals↗