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PubMed1984

Morphogenesis and morphology of the brain stem nuclei of Cetacea. II. The nuclei of the accessory, vagal and glossopharyngeal nerves in baleen whales.

The development and final structure of the IXth, Xth and XIth cranial nerve nuclei are studied in ironhematoxylin -, thionin - and protargol -stained serial sections of about 50 baleen whale fetuses (blue whale, Balaenoptera musculus, and fin whale, Balaenoptera physalus ) and one adult fin whale. The nucleus ambiguus is composed of three subdivisions, oral, intermediate and caudal, the last mentioned being contiguous caudally with the dorsal motor Xth nucleus. The oral division develops as three parallel cell columns which merge into a well circumscribed solitary structure with a rostrally expanded "head". It is composed of medium-sized multipolar neurons in a myelin-poor neuropil. In the fin whale a minor group of larger cells is found medial to the "head". In both species a peculiar small-celled nucleus rich in capillaries is found ventral to the "head". The intermediate division initially contains a lateral cell column and a medial region of scattered cells. The lateral column persists throughout life, while the medial field develops into three columns only one of which remains distinct in mature individuals. The cells are larger than in the oral division with the largest cells in the medial column. The two columns are surrounded by a field of scattered neurons which continues without a sharp border into the caudal division which is composed of scattered cells throughout. In its rostral half the cells are of the same multipolar type as in the intermediate division while caudally they appear flattened in the horizontal plane. The dorsal motor Xth nucleus develops as three longitudinal columns. In the fetal brain these are cytologically distinct due to different proportions of small, medium-sized and larger multipolar neurons. The spindle-shaped ventromedial column extends the entire length of the nucleus. It is composed mostly of small to medium-sized cells which caudal to the obex are elongated parallel with the neuroaxis . The dorsolateral and ventrolateral columns are restricted to the middle 1/3 of the nucleus, except in the blue whale where the former extends somewhat more rostrally. They are both characterized by the presence of large multipolar cells, the largest of which are found in the ventrolateral column. In adult specimens the cells are more equally sized and the columnar organization less distinct. The nucleus of the tractus solitarius is of about the same length as the two above mentioned nuclei. Except at the very early stages, the nucleus is ill-defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Accessory Nerve↗
PubMed1980

Altered cardiovascular responses to glossopharyngeal nerve stimulation in the spontaneously hypertensive rat.

Alterations in arterial blood pressure and heart rate in response to electrical stimulation of glossopharyngeal nerve (GPN) were examined in 6-10 months old, male spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) normotensive rats. GPN stimulation resulted in frequency-dependent decreases in arterial blood pressure in both SHR and WKY rats. SHR were more sensitive to GPN stimulation than WKY controls. Vasodepressor responses to GPN stimulation were greater in SHR than in WKY rats over a wide range of stimulus frequencies. At the frequency which produced the maximum response (50 Hz) the vasodepressor response was 68% greater in SHR than in WKY control. The results, indicate that neurogenically-induced vasodepression is enhanced in SHR, suggesting that decreased vasodepressor capacity mediated through the central nervous system is not involved in the maintenance of elevated blood pressure in SHR. In contrast to increased vasodepressor responses in SHR, GPN stimulation produced less bradycardia in SHR than it did in WKY rats. This difference may be central in origin because peripheral vagal stimulation produced essentially equal bradycardia in SHR and WKY normotensives.

Animals↗
PubMed1996

A quantitative study of the enhancing effect of nickel ions on the taste response to sodium ions of single fibers of the frog glossopharyngeal nerve: competitive inhibition by calcium ions of the nickel-enhanced response to sodium ions.

Single water fibers of the frog glossopharyngeal nerve respond to relatively high concentrations of NaCl ( > 80 mM). NiCl2 at 1 mM enhanced the Na+ response and reduced the threshold concentration for NaCl to 20 mM. CaCl2 at 0.5-1 mM induced an inhibition of the Ni2+ -enhanced response to Na+ ions. A quantitative explanations for these results is provided by the hypothesis that Ni2+ ions secondarily affect a sodium receptor or channel (designated XNa*) that is responsible for the Na+ response and that Ca2+ ions inhibit the Ni2+ -enhanced response to Na+ ions by competing with Na+ ions for XNa*. Double-reciprocal plots of the experimental data indicate that the affinity of XNa* for both Na+ ions (agonist) and Ca2+ ions (competitive antagonist) in the presence of 1 mM NiCl2 was five times higher than the previously reported values obtained in the absence of NiCl2 (Kitada, 1991). Ni2+ ions at 1 mM enhanced the maximal response to Na+ ions by 190%. It appears that a sodium receptor (or channel) interacts with a Ni2+ -binding element that is affected by Ni2+ ions and, thus, Ni2+ ions can induce both an increase in the affinity of the sodium receptor for the respective cations and an enhancement of the Na+ response.

Animals↗
PubMed1992

Salt taste discrimination after bilateral section of the chorda tympani or glossopharyngeal nerves.

Gustatory deafferentation of the anterior tongue by bilateral section of the chorda tympani nerve, which removes only 15% of the total taste buds in the rat, severely impaired the rat's ability to discriminate NaCl from KCl. The discrimination deficit was selective. Denervated rats were able to discriminate sucrose from quinine. Despite eliminating four times as many taste buds by bilateral section of the glossopharyngeal nerve, posterior lingual deafferentation had no effect on NaCl vs. KCl discrimination performance. Collectively, these data suggest that afferents in the chorda tympani nerve provide the highest degree of disparity between the peripheral signals representing NaCl and KCl. Electrophysiological findings of others implicate the sodium-specific afferents that appear to exclusively exist in the chorda tympani nerve as the critical elements subserving the NaCl vs. KCl discrimination.

Animals↗
PubMed2002

Pharyngeal branch of the glossopharyngeal nerve plays a major role in reflex swallowing from the pharynx.

Mechanical stimulation of the pharyngeal areas readily elicits reflex swallowing. However, it is much more difficult for electrical stimulation of the glossopharyngeal nerve (GPN) to evoke reflex swallowing than it is for stimulation of the superior laryngeal nerve (SLN) to do so. These paradoxical findings remain unexplained; hence, the main purpose of this study was to explain this contradiction by using a urethane-anesthetized rat. Mechanical stimulation easily elicited reflex swallowing from the pharynx. The posterior pillars, posterior pharyngeal wall, and the soft palate of the rat were extremely reflexogenic areas for swallowing. Sectioning the pharyngeal branch of the GPN (GPN-ph), however, eliminated the swallowing reflex from these areas. In contrast, sectioning the lingual branch of the GPN had no effect on the elicitation of swallowing. Electrical stimulation of the GPN-ph and SLN elicited sequentially occurring swallows. The relationship between stimulus frequency and the latency of swallowing for the GPN-ph was approximately the same as that for the SLN. These results indicate that the GPN-ph plays a major role in the initiation of reflex swallowing from the pharynx in rats.

Animals↗
PubMed1996

Specificity of glossopharyngeal nerve responses to astringent compounds in Xenopus.

Astringent compounds were applied to oral epithelium of the clawed toad, Xenopus laevis, and rapidly rising and highly sensitive responses could be recorded from the whole glossopharyngeal nerve, but not at all from the trigeminal nerve. The response to 10 mM tannic acid decreased progressively with repetitive application. These responses to tannic acid, however, recovered completely by treating with chemicals capable of forming strong hydrogen and hydrophobic bonds. These chemical bondings are generally recognized as a model for polyphenol (tannin)-protein interactions based on physico-chemical measurements in vitro. The high affinities of these chemicals for tannic acid may be effective in releasing both bonds in the interaction of tannic acid with the receptor molecules. Our results provide in vivo evidence for this model.

Animals↗
PubMed2005

Biophysical characterization of whole-cell currents in O2-sensitive neurons from the rat glossopharyngeal nerve.

In this study we use nystatin perforated-patch and conventional whole-cell recording to characterize the biophysical properties of neuronal nitric oxide synthase (nNOS)-expressing paraganglion neurons from the rat glossopharyngeal nerve (GPN), that are thought to provide NO-mediated efferent inhibition of carotid body chemoreceptors. These GPN neurons occur in two populations, a proximal one near the bifurcation of the GPN and the carotid sinus nerve, and a more distal one located further along the GPN. Both populations were visualized in whole mounts by vital staining with the styryl pyridinium dye, 4-Di-2-ASP (D289). Following isolation in vitro, proximal and distal neurons had similar input resistances (mean: 1.5 and 1.6 GOmega, respectively), input capacitances (mean: 25.0 and 27.4 pF, respectively), and resting potentials (mean: -53.9 and -53.3 mV, respectively). All neurons had similar voltage-dependent currents composed of: tetrodotoxin (TTX)-sensitive Na+ currents (IC50 approximately 0.2 microM), prolonged and transient Ca2+ currents, and delayed rectifier-type K+ currents. Threshold activation for the Na+ currents was approximately -30 mV and they were inactivated within 10 ms. Inward Ca2+ currents consisted of nifedipine-sensitive L-type, omega-agatoxin IVA-sensitive P/Q-type, omega-conotoxin GVIA-sensitive N-type, SNX-482-sensitive R-type, and Ni2+-sensitive, but SNX-482-insensitive, T-type channels. The voltage-dependent outward K+ currents were sensitive to tetraethylammonium (TEA; 10 mM) and 4-aminopyridine (4-AP; 2 mM). Exposure to a chemosensory stimulus, hypoxia (PO2 range: 80-5 Torr), caused a dose-dependent decrease in K+ current which persisted in the presence of TEA and 4-AP, consistent with the involvement of background K+ channels. Under current clamp, GPN neurons generated TTX-sensitive action potentials, and in spontaneously active neurons, hypoxia caused membrane depolarization and an increase in firing frequency. These properties endow GPN neurons with an exquisite ability to regulate carotid body chemoreceptor function during hypoxia, via voltage-gated Ca2+-entry, activation of nNOS, and release of NO.

4-Aminopyridine↗
PubMed1986

Primary afferent fibers in the glossopharyngeal nerve terminate in the dorsal division of the principal sensory trigeminal nucleus: an HRP study in the cat.

After applying horseradish peroxidase to the central cut end of the pharyngo-esophageal branch of the glossopharyngeal nerve in the cat, axon terminals labeled transganglionically with the enzyme were found ipsilaterally in the dorsomedial tip regions and ventromedial border regions of the dorsal division of the principal sensory trigeminal nucleus (dorsal Vp), as well as in the solitary, spinal trigeminal and medial cuneate nuclei. The area of termination in the dorsal Vp extended about 200 micron rostrocaudally in the caudal two-thirds of the dorsal Vp.

Animals↗
PubMed1992

The contribution of gustatory nerve input to oral motor behavior and intake-based preference. I. Effects of chorda tympani or glossopharyngeal nerve section in the rat.

Two-bottle intake tests and taste reactivity (TR) tests were used to reveal whether changes in ingestive behavior would follow bilateral section of either the chorda tympani (CT) or the glossopharyngeal (GP) nerve. Rats received two-bottle intake tests to compare 24-h ingestion of water to that of NaCl, MgCl2, quinine, or sucrose. Prior to each long-term intake test, rats received a 1 min, 1 ml intraoral infusion of the same chemical stimulus. Ingestive and aversive oral motor responses elicited by these 1 ml infusions were videotaped and subsequently analyzed. GP-section did not alter quinine or sucrose preference; overall, preference of MgCl2 and NaCl was also similar to controls. In contrast, TR tests in GP-sectioned rats revealed that most quinine, MgCl2 and NaCl stimuli elicited significantly fewer aversive oral motor responses. In addition, the latency of aversive responses to these 3 chemical stimuli was increased for these rats. Intake-based preference tests failed to show any difference between rats with CT nerve section and controls. In TR tests, however, CT-sectioned rats displayed significantly fewer ingestive oral motor responses to NaCl, MgCl2, and quinine than controls. Neither sucrose intake nor sucrose-elicited TR were altered by CT or GP nerve section. This report confirms the failure of long-term intake tests to uncover behavioral deficits following the section of gustatory nerves. In contrast, the use of a different behavioral test makes clear for the first time that gustatory nerve section has dramatic consequences on ingestive behavior. The examination of taste elicited oral motor behaviors reveals a coherent and nerve specific pattern of neurological deficit following peripheral nerve section.

Animals↗
PubMed2000

Glossopharyngeal nerve regeneration is essential for the complete recovery of quinine-stimulated oromotor rejection behaviors and central patterns of neuronal activity in the nucleus of the solitary tract in the rat.

The peripheral, central, and behavioral consequences of glossopharyngeal nerve transection (GLX), regeneration, and the prevention of regeneration on the quinine-elicited responses of adult rats were concurrently examined. Oromotor taste reactivity (TR) was videotaped during intraoral infusion of 7 ml of either quinine (3 mm) or distilled water at 17, 52, or 94 d after surgery. We confirmed previous findings by showing that 17 d after neurotomy, (1) the number of circumvallate (CV) and foliate taste buds, (2) gapes (a characteristic aversive TR response), and (3) the number of Fos-like immunoreactive (FLI) neurons in the gustatory NST (gNST), particularly in the medial portion (subfield 5) of the rostral central subdivision (RC), were all severely attenuated in GLX rats. We extended these findings by showing that these lesion-induced effects were enduring when the GL did not regenerate (up to 94 d). In contrast, when the GL regenerated, as few as 52 d were sufficient to re-establish quinine-elicited TR, especially gaping, and FLI expression in RC, particularly within subfield 5, to values comparable with quinine-stimulated sham-operated rats. Evidently, the gNST maintains its potential to restore accurately the organization of neural activity that is disrupted by nerve injury, as assessed by FLI, ultimately leading to the return of normal protective oromotor responses, provided the nerve regenerates. This recovery was complete despite the reappearance of a reduced population of CV taste buds ( approximately 75% control values) and may relate to peripheral and/or central changes that occur in tandem with regeneration of the GL.

Animals↗
PubMed1981

Endoscopic section of the sensory trigeminal root, the glossopharyngeal nerve, and the cranial part of the vagus for intractable facial pain caused by upper jaw carcinoma.

In a patient with intractable facial pain caused by a deep-seated carcinoma of the upper jaw, relief was obtained following endoscopic section of the sensory trigeminal root, the glossopharyngeal nerve, and the cranial part of the vagus. Previous stereotactic thalamotomy had failed. The endoscopic method is briefly described and discussed.

Cerebellopontine Angle↗
PubMed1986

Syncope: a clue to malignant compression of the glossopharyngeal nerve.

Three patients who were admitted to hospital because of syncope were found to have malignant head and neck tumours. A patient who presented with malignant external otitis with syncope and postural hypotension is also described. It is postulated that the syncope and postural hypotension result from compressive irritation of the glossopharyngeal nerve either in the neck or at the base of the skull.

Aged↗