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At least 1,783 records · Page 99Linked to original sources
PubMed1992

The effect of injury on the properties of afferent fibres in the lingual nerve.

The receptor properties of mechanosensitive afferent fibres in the lingual nerve have been studied using electrophysiological techniques in cats. In normal animals some fibres responded only to mechanical stimulation of filiform or fungiform papillae but others also responded when a cold stimulus was applied to the receptive field. Twelve weeks after crushing the lingual nerve, the regenerated fibres had slower conduction velocities but the receptor properties were not significantly different from normal. Twelve weeks after sectioning the lingual nerve, there was a greater reduction in conduction velocities and in addition the mechanoreceptive fields were smaller, force thresholds were higher, adaptation times longer and a smaller proportion of fibres responded to a cold stimulus. These results suggest that section injuries are more likely to result in persistent sensory abnormalities than crush injuries.

Action Potentials↗
PubMed1982

The response characteristics of rat taste cells to four basic taste stimuli.

1. The shapes of receptor potentials of rat taste cells in response to the four basic taste stimuli (0.5 M NaCl, 0.02 M quinine-HCl (Q-HCl), 0.01 M HCl and 0.5 M sucrose) were classified into three types, i.e. (1) a depolarization alone, (2) a depolarization preceded by a transient hyperpolarization and (3) hyperpolarization alone. 2. The rise and fall times of depolarizing responses to NaCl were much shorter than those to the other three stimuli. The fall time of depolarization evoked by HCl was the longest. The rise and fall times of all hyperpolarizing responses were shorter than those of all depolarizing responses. 3. The input resistance of taste cells decreased during depolarizations elicited by NaCl stimulation, but increased during depolarizations and hyperpolarizations elicited by stimulation with Q-HCl, HCl and sucrose. 4. The taste stimulus-induced input resistance change returned faster to the control in the order of NaCl greater than sucrose greater than Q-HCl greater than HCl when the stimulus was rinsed from the tongue. 5. From these response characteristics the rat taste cells responding to each of the four basic taste stimuli are largely divided into two types, low-sensitive taste cell and high-sensitive taste cell.

Animals↗
PubMed1982

The adaptation of the frog tongue to various taste solutions: the effect on gustatory neural responses to bitter stimuli.

1. After the frog tongue was adapted for 10 sec to various salts and sugars, the initial phasic component of gustatory neural responses to almost all of quinine hydrochloride (Q-HCl), quinine sulfate (Q-H2SO4). Brucine, caffeine and picric acid was suppressed. 2. Following 10 sec adaptation to acetic acid, the phasic responses to Q-HCl and Q-H2SO4 were unchanged, those to brucine and caffeine were enhanced, and that to picric acid was depressed slightly. 3. The response to any one of Q-HCl, Q-H2SO4. brucine and caffeine was suppressed after adaptation to the other three, while those to picric acid and nicotine were unchanged or enhanced after adaptation to another bitter solution.

Adaptation, Physiological↗
PubMed1983

Dependence of gustatory neural response on depolarizing and hyperpolarizing receptor potentials of taste cells in the rat.

The rat taste cells responded to the four basic taste stimuli (0.5 M NaCl, 0.02 M quinine-HCl (Q-HCl), 0.01 M HCl and 0.5 M sucrose) with depolarizing or hyperpolarizing receptor potentials. The rates of obtaining hyperpolarizing responses under 41.1 mM NaCl adaptation were 3% for NaCl, 42% for Q-HCl, 21% for HCl and 37% for sucrose. Most of the taste cells responded to more than two kinds of taste stimuli. The ratio of mean magnitudes of depolarizing and hyperpolarizing responses for the four basic taste stimuli under 41.4 mM NaCl was as follows: NaCl:Q-HCl:HCl:sucrose = 100:9:48:2. The ratio of mean magnitudes of tonic chorda tympani nerve responses for the four basic taste stimuli under 41.4 mM NaCl was: NaCl:Q-HCl:HCl:sucrose = 100:5:37:2. Comparison of both taste cell and nerve responses suggests that the depolarization of a taste cell is concerned with a generation of gustatory neural impulses, and that the hyperpolarization is concerned with a depression of the impulses.

Action Potentials↗
PubMed1983

Topographical difference in taste organ density and its sensitivity of frog tongue.

Distribution density of the taste disks of the fungiform papillae in the frog tongue was larger at the proximal portion than at the apical and middle portions. The number of myelinated afferent nerve fibres and taste cells per cm2 area of the tongue increased in the order of proximal greater than middle greater than apical portion. The amplitudes of gustatory neural responses for 0.5 M NaCl, 0.5 M KCl, 0.5 M NH4Cl, 0.05 M CaCl2, 1 mM acetic acid and 1 mM quinine-HCl (Q-HCl) were significantly larger with lingual stimulation of the proximal region than with the stimulation of the apical region. With these stimuli the mean ratio of the apical response to the proximal response was 1.00:1.54. On the other hand, this ration with deionized water was 1.00:5.00. The mean magnitudes of receptor potentials in taste cells for 1 mM acetic acid and 10 mM Q-HCl were the same among the apical, middle and proximal portions of the tongue. The mean magnitudes of receptor potentials for 0.5 M NaCl were significantly larger at the apical portion than at the other portions, whereas those for deionized water tended to be the largest at the proximal portion. It is concluded that the larger magnitude of the gustatory neural responses at the proximal portion of the tongue is due to morphological and physiological properties of the taste organ.

Animals↗
PubMed1986

Biochemical studies of taste sensation--XII. Specificity of binding of taste ligands to a sedimentable fraction from catfish taste tissue.

The specificity of amino acid binding sites in a sedimentable fraction prepared from catfish taste epithelium was examined. Using seven 3H-labeled amino acids as ligands and the unlabeled amino acids in binding competition assays, the presence of possibly three classes of amino acid binding sites was deduced. Site 1 binds L-THR, L-SER, L-ALA and possibly D-ALA and beta-ALA, Site 2 binds L-SER, L-ALA, GLY, D-ALA, and beta-ALA and Site 3 binds L-ARG and L-LYS. Additional evidence supporting the specificity of Site 2 was obtained from the specificity of enhancement of L-ALA binding. The results demonstrate the presence of some major classes of taste receptor sites, and provide a basis for understanding taste receptor specificity at the biochemical level.

Amino Acids↗
PubMed1988

Signalling in taste receptor cells: cAMP-dependent protein kinase causes depolarization by closure of 44 pS K-channels.

1. In whole-cell patch-clamp recordings cytosolic cAMP causes a substantial depolarization of taste receptor cells isolated from the frog tongue. The depolarization requires the presence of ATP in the cell and is suppressed by protein kinase inhibitor. 2. The depolarization also develops in the absence of cAMP while the catalytic subunit of the kinase is allowed to diffuse into the cell in the presence of ATP. 3. In membrane patches excised from these cells the catalytic subunit is found to inactivate K-channels of 44 pS conductance, presumably by phosphorylation. 4. It appears that cAMP is one of the intracellular messengers in gustatory chemoreception, and that it causes membrane depolarization through activation of a protein kinase which controls the activity of one set of K-channels.

Animals↗
PubMed1990

Electrical responses of supporting cells in the frog taste organ to chemical stimuli.

1. The mean resting potential of supporting cells in the frog taste organ was -19.1 mV. The supporting cells responded to the four basic taste stimuli with a depolarization but responded to water with a depolarization or a hyperpolarization. 2. The membrane resistances of supporting cells decreased during stimulation with sucrose, NaCl and acetic acid, but increased during stimulation with Q-HCl and water. 3. Reversal potential of the depolarizing response for 0.5 M NaCl in supporting cells was +7.6 mV. The depolarizing responses for Q-HCl and acetic acid were independent of the membrane potential level. 4. These results suggest that the characteristics of taste responses in supporting cells are similar to those in taste cells.

Animals↗
PubMed1994

Trigeminal sensory neuropathy with abnormal taste following acute sinusitis.

We report a case of isolated trigeminal sensory neuropathy associated with impairment of taste sensation following acute sinusitis. Sensory disturbance was distributed mainly in the ophthalmic division, and partly in the maxillary and mandibular divisions. No other cranial nerves were involved. An otological procedure resulted in complete recovery. The unique combination of trigeminal neuropathy and abnormal taste seemed to be caused by the infectious process involving the gasserian ganglion of the trigeminal nerve.

Dysgeusia↗
PubMed1985

Effect of antidromic stimulation of the glossopharyngeal nerve on afferent discharges occurring with and without sensory stimulation of the frog tongue.

Repetitive stimulation of the bullfrog glossopharyngeal nerve at a rate of 100 Hz for 10 s and at a supra-maximal intensity resulted in little depression of the glossopharyngeal nerve responses to application of quinine and mechanical taps to the tongue, in a 30-40% decrease in the responses to salt, acid, water and warmed saline and in a 80% decrease in the number of spontaneous discharges from the tongue. Such a selective depression existed throughout changes in the frequency and the duration of the antidromic stimuli. The phenomena were attributed to antidromic impulses in high-threshold glossopharyngeal nerve afferents.

Animals↗
PubMed1987

Taste receptors in crayfish: recording of single nicotinamide-activated channels.

The patch clamp technique was adapted to chemoreceptive sensory cells in the claw of Austropotamobius torrentium. In cell-attached and in outside-out patches, concentrations of nicotinamide from 10(-6) mol/liter to 5 X 10(-5) mol/liter activated openings of single channels located in the cell body of the sense cell. The characteristics of these single channel openings were similar to those of neurotransmitter activated channels: the I/V curve was approximately linear, showing a reversal potential of about +15 mV and a conductance of about 33 pS. The mean open time was 1-2 ms. A similar concentration dependence was found for the activation of single channel openings as shown previously for the action potential discharge elicited by nicotinamide at the same preparation.

Action Potentials↗
PubMed1989

The ability of gustatory stimuli to modify the cardiac sympathetic and vagus nerve activities.

The effects of chemical stimulation of the oro-lingual mucosa on the heart rate and arterial blood pressure were studied together with changes in the cardiac nerve activities in the rat. Of four qualities of basic taste stimuli, only HCl and NaCl but not quinine and sucrose were effective in increasing the heart rate and blood pressure. These changes in the cardiovascular system were associated with an increase in the efferent cardiac sympathetic activity and a decrease in the vagal activity, although they were no longer appreciable after transection of the glossopharyngeal nerve.

Adrenergic Fibers↗
PubMed1989

A dissociation procedure for mammalian taste cells.

A procedure for dissociating viable taste cells from the rodent tongue was described. After the tongue was excised, the foliate and circumvallate papillae from the posterior region were blocked to small pieces and incubated for 2-3 h in a calcium-free salt solution containing the enzyme papain. The pieces were then transferred to a Ca-replete medium. The epithelium was easily removed from the underlying muscle and gland tissue with forceps. Light mechanical agitation caused single cells, epithelial and gustatory, to dissociate from the keratinized epithelium. Taste cells were identified by their morphology. Their viability was assessed with the patch clamp technique in the whole cell recording mode. This procedure should enhance the electrophysiological study of gustatory transduction mechanisms.

Animals↗
PubMed1989

Effects of octopaminergic substances on the labellar lobe spreading response in the blowfly Protophormia terraenovae.

The effectiveness of labellar taste input in evoking the feeding response of labellar lobe spreading in Protophormia was greatly increased by injecting flies with clonidine or DL-octopamine. This effect was suppressed when either drug was administered together with yohimbine; when injected alone, the latter determined a strong decrease in the feeding responses. Drug treatment did not determine variations in labellar taste input or evoke spontaneous activity in the denervated muscle. These results suggest that the injected substances lower the feeding-related reflex threshold at the CNS level.

Action Potentials↗
PubMed1996

Inhibition of potassium currents by the antiarrhythmic drug E4031 in rat taste receptor cells.

The effect of the class III antiarrhythmic agent E4031 was investigated on a non-cardiac preparation as a potential tool for studying potassium currents. Patch clamp recordings in the whole cell configuration were performed on dissociated rat taste cells. These cells possess a variety of potassium currents; they also conduct action potentials. Unlike its more specific action on a type of delayed rectifier channel in cardiac cells, three types of potassium currents were reversibly diminished in taste cells in the presence of E4031. These included transient, sustained, and inwardly-rectifying potassium currents. Activation properties were not altered but the inactivation curve was shifted to the left by approximately 10 mV. Inhibitions of whole cell currents were voltage-dependent, larger at depolarized potentials, but were never complete. E4031 significantly broadened the gustatory action potential and, at higher concentrations, inhibited spike height, suggesting an additional inhibitory effect on sodium channels that was evident in voltage-clamp records. We conclude that E4031 is an effective inhibitor of potassium currents in the micromolar range and that it likely acts at a conserved segment of the potassium channel.

Action Potentials↗