The round window membrane of the guinea pig was experimentally ruptured by increasing CSF pressure. Injection of artificial perilymph eventually produced rupture of the membrane. This was observed under an operating microscope. There are two groups as far as the rupture pressure is concerned: One group showed the pressure as being 1000 mm H₂O. Another group showed a higher pressure of 1500-3500 mm H₂O. Most of perforations were found along the edge of the window. The ruptured membrane in 3 guinea pigs healed spontaneously within 2 weeks.

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Intracellular recordings were made from inner hair cells, outer hair cells and supporting cells in the fook area of the guinea-pig cochlea, the recording sites being confirmed by the injection of Alucion blue dye and subsequent surface prepalation technic. Inner hair cells had resting potentials between 57 and 92mV, outer hair cells had between 75 and 88mV. Both hair cells were recorded DC potentials about 0.6mV in amplitude in response to a tone burst of 10 KHz of ca. 30dB up the CM threthold. The AC response was recorded maximary at the inner hair cells in response to a 10KHz tone burst, but at the outer cells the AC response was small. Those conclusion were thinking out that inner hair cells earring a principal dutis in transduction at the Organ of Corti.

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The endocochlear dc potential (EP) was mesured in normal albino guinea pigs after intravenous administration of 50% glycerol solution. Histological changes of the cochlear partition was also investigated. After the administration of small dose of glycerol solution (2.4ml/kg, 3.6ml/kg), the EP was diminished slightly within few minutes. This change was transient and the EP recovered to almost normal level within 10 minutes. On the other hand the marked diminution of EP was observed in many cases after the administration of large dose of glycerol solution (4.8ml/kg, 6.0ml/kg). The diminution of EP started about 10 minutes after the administration and reached to 0mV within few minutes. It is generally considered that the stria vascularis plays an important role in the generation of the EP. The stria vascularis appeared almost normal even in these animals. This discrepancy should be investigated in future.

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It is generally considered that Na⁺, K⁺-ATPase participates to generate the Endocochlear DC Potential (EP) in the stria vascularis. In 1983, we reported the inhibitory effect of Vanadate (Na₃VO₄) on this enzyme. Vanadium which is a transition metal element has several oxidation states such as +3, +4, +5. The present study was to define electrophysiologically which forms of vanadium were effective on EP and CM. With perilymphatic perfusion of Vanadate (Na₃VO₄, NHVO₃, KVO₃: +5) at the concentration of 1mM, EP was increased for a few minutes at the beginning, following of gradual reductions of EP and CM in thirty minutes. Whereas, no changes in EP and CM by perfusion with others oxidation number of Vanadium (VOSO₄: +4, VCl₃, V (C₅H₇O₂) 3: +3). Even after the perfusion for thirty minutes, a large magnitude of negative EP was observed in every case when anoxia have enforced. From the results obtained that the generation of EP is inhibited by vanadium compounds the +5 oxidation state.

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Sudden atmospheric pressure changes was given to many guinea pigs in a chamber. After pressure loading, we measured endochlear dc potential in guinea pigs without Preyer reflex, and we investigated whether negative EP after anoxia should appear or not.
Endocochlear dc potential decreased immediately after barotrauma but it returned to normal values in two weeks.
The anoxic EP in barotrauma animals less then 3 days after the pressure loading decreased to negative values, but the anoxic EP in barotrauma animals more than 7 days after the pressure loading never decreased to negative values. They remained in positive values. These findings suggest that inner ear mechanisms maintaining positive EP is damaged immediately after barotrauma and that its function is restored in 7-14 days.

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Endocochlear potentials (EP) decreases under various conditions, such as anoxic anoxia, or the injection of furosemide. The effects of anoxic anoxia on EP were examined in 30 guinea pigs. The EP was recorded with micro electrode technique before and after injection of furosemide (30-50 mg/kg). A hypothetic model equation (y=L (1-e^-rt)) was adopted. By applying a least square method, the values were calculated by this model equation, and were compared with the recorded EP. A microcomputer was used for calculation. The values of the model and the recorded EP fitted well both in usual apnea and in apnea under decreased EP induced by furosemide. EP falling pattern in usual apnea was similar with that in apnea under EP decrease induced by furosemide. This indicates that furosemide is not a determinate block in the chemical process of O₂ dependent part in EP generation, but it only disturbs a part of above process.

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The effect of perilymphatic perfusion with oxygenated artificial perilymph upon the EP of the ischemic cochlea was investigated in the guinea pig.
Perfusion at a high flow rate in scala vestibuli could well recover and maintain the EP to the level before the ischemia, whereas perfusion in scala tympani could not recover the EP as effectively.
This finding seems to suggest that, in an anoxic cochlea, oxygen when supplied in scala vestibuli gets easier access to the stria vascularis than when supplied in scala tympani.

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The effects of neomycin (NM) on cochlear potentials were studied in guinea pigs. NM were applied in scala media by iontophoresis or by diffusion. Changes of cochlear potentials, i. e. endochochlear potentials, cochlear microphonics, summating potentials and action potentials, before and after the application of NM were compared with those caused by transient asphyxia. Shortly after the recording of cochlear potentials, the cochleae were removed and perfused with nitroblue-tetrazorium (NBT). All the cochlear potentials were suppressed. The cochlear microphonics were more severely suppressed in NM application than in asphyxia. The hair cells showed normal NBT reducibility in both NM application and asphyxia.
These results support the hypothesis that the CM supprssion by NM is caused by a blockade of presumable calcium ion binding site at the hair cell membrane.

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Na⁺-K⁺ pump or Na⁺-K⁺ ATPase was localized in the cochlea by autoradiography using H-ouabain as a ligandand histochemistry using onestep method for potassium-dependent p-nitrophenylphosphatase (K-NPPase). Both method revealed the moderate activity in the spiral ligament especially in the middle portion adjacent to the spiral orominence. supprting the biochemical estimation. In the vascular stria, however, the resuit was quite different. Ouabain binding site was observed only at the lowemost portion, while K-NPPase activity was strongly observed all over the stria. This discrepancy may be explained by the barrier between the spiral ligament and stria; perilymphatically perfused ouabain can not penetrate to the stria so freely because of it. Functional significance of the results was briefly discussed.

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It has been known that the sensorineural hearing loss is frequently observed in patients with renal failure. Because the hearing loss is influenced by many other factors, such as ototoxic drugs, genetic diseases, noise exposure, aging, diabetes and renal hemodialysis, it is difficult to determine whether the hearing loss directly relates to renal failure itself. The present experiment aims to investigate the relation between the hearing loss and renal failure. AP (N1), CM andEP were examined in 12 guinea pigs with renal failure produced by ligation of bilateral ureters. AP was abolished in 3 cases and decreased in amplitude in 4. The latency was prolonged in 3. CM was decreased in 4 and no response was obtained in 3. In all the magnitude of EP and its response to anoxia were normal. The effect of renal failure upon cochlea potentials was correlated with neglect factor (Creatinine +BUN/10). No pathological finding was observed in the cochlea by light microscopy. These results strongly suggest that these electrophysiological findings are due to the hair cell and/or neural damage, probably at the level of enzyme and metabolism.

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Department of Otolaryngology, Tohoku University School of Medicine In the previous meeting, we reported that the AP amplitude was temporally increased at the intermediate temperature. For further clarification of this phenomenon, narrow band AP (NAP) was recorded in 12 guinea pigs subjected to hypothermia. Recording was performed at 36°C, 30°C, 28°C, 25°C, 23°C and the NAPs were recorded by using high pass noise (8KHZ, 4KHZ, 2KHZ). The latenciesof the every NAPs (>8, 8-4, 4-2, <2) were almost linearly increased as a function of the temperature decline. Although the amplitudes of the lower frequency components (4-2, <2) were decreased as the temperature was reduced, those of higher freque°Cncycomponents (>8, 8-4) exhibited no change or the increase at 30 and 28°C. The results obtained in the present study show that this increase of NAP amplitude at the intermediate temperature seems to be the cause of transient increase in AP amplitude.

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Eight normal rabbits were implanted with electrodes on the round window. They were exposed to noise (90 or 100 dB SPL of pure tones at 2 KHz) for two hours everyday. AP was measured immediately after each exposure and twenty-two hours later. The following results were obtained.
1) Changes in waveform of AP were reversible in the beginning and became progressively irreversible as a result of noise exposure more than five days.
2) In the stage of reversible changes, the amplitudes of AP were decreased and the latencies were prolonged in region of high sound pressure after noise exposure. In the stage of irreversible changes, the both phenomena parallellyoccured in the all region of sound pressure.

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Perilymphatic fistula is known to be a cause of acute, profound and reversible sensory hearing loss. However, it remains to be explained why such hearing loss was caused by perilymphatic fistula only. The exploratory tympanotomy we operated suggested that the hearing loss was possibly induced by aspirating air into the perilymphatic space. This assumption was verified by the experiment using guinea pig. Action potentials of the auditory nerve were registered; 1) Before and after air was aspirated into the scala tympani, 2) After the air was pushed out by pouring the perilymph back into the scala tympani. The experiment demonstrated that acute, profound and reversible hearing loss was developed by aspirating a very small amount of air into tha scala tympani.

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Hydrostatic pressure of the perilymph was changed by introducing a small catheter into the epidural space and changing the cerebrospinal fluid pressure in guinea pig and cat. Changes in hydrostatic pressure of the perilymph affected the cochlear potentials (CM. AP), but physiological pressure changes (+100 mm H₂O) maked no hearing loss. High pressures (500 -1, 000 mm H₂O) were required to produce sensorineural hearing loss (SNHL) that was greater for low frequencies and was reversible in short time experiment. Perilymph fistula was experimentally produced by applying high perilymph pressure above 1, 000 mm H₂O, and same cochlear potential changes as alternation of the perilymph pressure with no perilymph leak was observed. Cause of the SNHL and histopathology were discussed.

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Methods for recording the cochlear potentials, i. e., electrocochleogram (ECoG) and the auditory brain stem response (ABR) in unrestrained rats were developed. The electrodes for recording the ECoG and ABR were implanted chronically in the vicinity of the round window membrane and on the epidural surface at the lower margin of the parietal bone, respectively. The ECoG and ABR were recorded simultaneously on unrestrained rats using a slip ring which allows the rat free movement without twisting the cables. Latencies of each component of the ABR were compared with those of the ECoG, and binaural interaction was also checked by unilateral puncture of the tympanic membrane. The early components of the ABR, which corresponded to the ECoG, were related to the homolateral cochlea, while the late components to the contralateral cochlea. The amplitudes and latencies of the ECoG were reproducible for 3-4 weeks and those of the ABR for 6 weeks. These results indicate that this recording technique for ECoG and ABR is useful for evaluating the ototoxicity of drugs in unrestrained rats.

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We have previously reported that intravenous administration of phenytoin natrium (PHT) suppressed the tinnitus of human. In order to elcidate its mechanism, the influence of PHT on ABR was studied in the guinea pig. The effects on ABR at systemic administration were determined by latency and amplitude of each waveform peak. at the dose under 20mg/kg body weight, no obvious change was observed in both parameters. At the dose over 30mg/kg, however, the latencies of all the waves (I-IV) were prolonged and the amplitudes of them were decreased.And these changes were dose- dependent. As for the peak to peak latency, that of between wave III and wave IV was most prominently affected by PHT. From these results, we have tentatively concluded that the PHT strongly inhibited the neural activities in the brain stem, especially in the upper brain stem. This inhibition may be related to the mechanism of effectiveness of the PHT to the tinnitus.

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Thirty two guinea pigs were used in this study. These animals were divided into two groups. First group was administered aleviatin 75mg/kg, and second group was administered CH₃-B₁₂ (mecobalamin) 1000ug/kg before treatment of aleviatin 75mg/kg. Each animal was measured ABR under the condition of 40dB at 10000Hz, using TA-1000 (produced by Teledyne Avionics Co. Ltd.), before administration of drug and at every an hour after treatments. Five animals of each group were sacrificed for measurement of SDH activity, using spectrophotometer, of the cerebral mitochondria which was separated by Ozawa's method. Results were as follows. (1) Irregularity of ABR was appeared in 9/13 animals of first group from one to two hours after treatment. (2) No irregularity of ABR was present in second group. (3) SDH activity of cerebral mitochondria of second group was stronger than first group. It is suggested that aleviatin may be affected to the central neural system and that mecobalamin may be relieved the influence of aleviatin.

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Auditory brain stem response (ABR) was investigated on Shivere mice and Reeler mice.
In the case of Shivere mice, it was observed that the latency was prolonged in waves after ABR Wave II and the disappearance of Wave V was also observed. Although the interpeak latency was also prolonged, there were some differences accoding to the region. The threshold was found normal.
On the other hand, in the case of Reeler mice, findings diversified with respect to the waveshape and latency since some did not show any difference as compared to the control, some showed a prolonged latency and in some cases the only wave that was recognized was Wave I.
The findings on ABR of the Shivere mice were considered due to the absence of myelin formation. In view of the findings on ABR of the Reeler mice, it was presumed that the brain stem disorder would probably be a secondary change rather than a primary change.

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ABRs elicited by temporal dichotic click stimuli were studied using simultenous recordings of two electrode pairs: vertex-ipsilateral(to delayed click) ear lobe and vertex-contralateral ear lobe. Ipsi-contra asymmetries in averaged ABR over 18 subjects were found in III(+) and V(+), except I(+). Calculated dichotic waves were derived from ipsilateral and contralateral to monotic stimuli with correction of interaural time differences. It was found that differences between dichotic and calculated ABRs of both leading and delayed side were small in amplitude and have no significant peaks, in spite of ipsi-contralateral asymmetries. It was suggested that monaural ABRs were summated into binaural ABRs almost equally in both diotic and dichotic conditions.

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Spontaneous discharges from the cochlear nucleus neuron of the cat were examined under some conditions. Spontaneous discharges of the neuron were markedly suppressed with tone burst by which the neuron showed sufficient response dischares. After lidocaine was injected intravenously spontaneous discharges were suppressed or completly disappeared but responses of the neuron to tonal stimuli were almost unchanged. Some neurons showed that spontaneous disgharges were increased greatly under anoxic condition and when the intensity of stimulus tone was increased above the level of about 90 dBSPL, a neuron showed numerous rondom discharges and responses of the neuron to sound stmulus were impossible to distinguish. It is considered that there are some kinds of different mechanisms to suppress spontaneous discharges of neurons by use of tone or lidocaine.

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Responses of cochlear nucleus neurons to complex tones were recorded with microelectrode technique in anesthetized cats . Complex tones for stimulus were composed of two pure tones. (The first group: 670, 1250 and 2400Hz; The second group: 350, 500 and 1100Hz) The type of PST (post-stimulus time) histogram was dependented on frequency andintensity of stimulus tone. We consider that this phenomena is relatedto the processing mechanism in cochlear nucleus. Responses which wereobtained from on-type neuron were changed under two tone stimuli and different type of response appeared. The neuron which didn't show any response to f₁ tone showed more inhibition under two tone condition than it did to f₂ tone alone. According to the results, the followingwas concluded: Response patterns of the cochlear nucleus neuron of thecat were changed under stimulus condition and it is considered as a result of neural mechanism of the cochlear nucleus.

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We have investigated the way in which an attempt is made at finding phenomenological mathematical expressions for intensity characteristics of two-tone suppression inferred from forward masking experiments. Analysis of frequency distribution of two-tone suppression leads to the derivation of two simple equations that describe the relationships between the stimulus energy or a variable proportional to it, and either the average receptor potential or the average firing rate of receptor. The equations imply that two-tone suppression perform a power-function transformation on the results. An exponential function is derived for the saturation at sufficiently high stimulus levels. The equations generate numerical values in close agreement with empirical intensity characteristics of receptor. Usually, two-tone suppression appear to obey a power of approximately 0.5

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In a cerebral hemisphere dominance test using an electronic key tapping method capable of examining sounds by the hertz, we previously found a sudden reversal of the side of dominant hemisphere for a pure tone at exactly 40 and 60Hz and the multiple frequencies of 40 and 60Hz. In another key tapping test using complex sounds comprising a large number of narrow band noises, we also found a sudden reversal of the side of dominant hemisphere for a complex sound consisting of exactly 40, 60, or 80 narrow band noises. This suggested that the existence of a mechanism which integrates the processings of space and time informations in auditory stimuli and that humans have accutate time sensing system based on the sense of one second.

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This paper describes the scanning electron microscopic appearance of nerve fibers and nerve fiber bundles in the human facial nerve within the temporal bone. To examine the fine morphology of the nerve, a modification of Evan's tissue digestion method was used to remove the extracellular material around the nerve fibers.
1. The fine morphology of the nerve fiber and fiber bundles was clearly visible.
2. The nerve did not run as a single bundle through the temporal canal. Several anastomoses and bifurcations were seen.
3. The arrangement of the bundle was complicated, and branches of the bundle changed their courses in the deep portion.
4. The arrangement of nerve fibers was also complicated.
These findings suggest that the arrangement of nerve fibers and nerve bundles is very complicated, and that there is no spatial arrangement of nerve fiber within the temporal canal.

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After removal of the neural sheath and extracellular connective tissue components by HCl hydrolysis, we examined the three-dimensional structure of the guinea-pig geniculate ganglion by scanning electron microscopy. At the geniculate ganglion, the greater petrosal nerve branched off and a bundle of small nerve fibers ran circularly on the surface of the facial nerve. The geniculate ganglion consisted of many spherical corpuscles ranging from 10 to 20 μm. Each corpuscle, representing a complex of a neural body and satellite cell sheath, gave rise to a single dendroaxonal process enclosed by the Schwann cell investment. Two types of stems of the processes were differentiated; one abruptly left its parent complex and the other showed convoluted texture, forming the initial glomeruli of Cajal. The stem processes which formed the initial glomeruli took a meandering course and showed irregular constrictions. Two types of Schwann cells attached to the stem processes; one was spindle-shaped, and the other was round-shaped with spider-like processes.

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The temporal bone histopathology of two anencephalia cases was reported especially about the 7th and the 8th nerves.
Pathologic examination of the central nervous system revealed the intact pons, medulla oblongata and spinal cord. Temporal bone pathology revealed that the internal auditory meatus was short and wide containing thin nerve fibers. The facial canal began just inside the internal auditory meatus and ran over the cochlea separately. Complete absence of the bony facial canal was observed above the oval window. The number of ganglion cells was reduced in the cochlear and vestibular ganglions, however the changes were not observed in the geniculate ganglion.
From these observations, the authors concluded that the cahnges in the internal auditory meatus, cochlear and vestibular ganglia are due to a degenerative process during embryonic life and that the facial nerve gets less influence as long as the brain stem remains intact.

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22 rabbits received injection of Indian ink into the stylomastoid foramen. From three hours to 21 days after injection, the temporal bones were fixed by intravascular perfusion. Observation of the serial sections of their temporal bones revealed Indian ink infiltration as far as the facial nerve.
On one case which was fixed 21 days after injection, Indian ink infiltrated as far as the vertical portion of the facial nerve. But Indian ink infiltrated into the subarachnoid space via jugular foramen along the perineural space of the auricular branch of the vagus nerve and the tympanic nerve.

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Recently, authors often use Hydroxyl Apatite (HAP) in middle ear surgery. (obliteration of the mastoid or reconstruction of the external auditory canal.) The purpose of our experiment is to clarify safety use of HAP, and the following study was examined. The HAP was embeded in the drilled hole of the bulla of the adult guinea pigs. After one month, these animals were sacrificed. Histopathological studies were performed under light microscope.
The following results were obtained.
1) The embeded HAP was tightly surrounded by connective tissue, in which no giant cells were observed. Therefore it seems that foreign body reaction was inactive.
2) No evidence of new bone formation on any surface of the embeded HAP was obtained, but active bone formation was observed on the surface of the bulla neighboring the embeded HAP. It seems that the embeded HAP accelerate new bone formation.

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Motoneurons innervating the tensor tympani muscle in the rabbit were examined using the method of retrograde axonal transport of horseradish peroxidase (HRP).
Injections of HRP into the tensor tympani muscle produced retrograde labeling of cells ipsilaterally. These labeled cells are clustered in the region ventral or vetrolateral to the trigeminal motor nucleus at its rostral half levels. A few labeled cells are seen extending in the portion rostral to the rostral pole of the nucleus. No labeled cells are observed within the trigeminal motor nucleus which is traditionally thought to innervate the tensor tympani muscle in the rabbit. The labeled cells are multipolar in shape and are smaller than cells in the trigeminal motor nucleus.
From these results, it can be concluded that the cells innervating the tensor tympani muscle in the rabbit arise from the reticular region vetral or ventrolateral to the trigeminal motor nucleus proper.

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In 1982, we have reported the results of histological examinations of the ear of the mass stranded dolphins in MIYAZAKI and concluded that parasitogenic octavus neuropathy should be a possible cause of the mass stranding of them.
On 22nd May 1983, mass stranding of dolphins (a kind of Globicephalus) had occured again at the same seashore of Aoshima, MIYAZAKI. We have examined 2 heads of them and found a lot of parasites (Nasitrema gondo YAMAGUCHI) in the tympanic cavity.
Histological examination of the periotic and tympanic bone revealed again severe degeneration of octavus nerve, especially in the modiolus of the cochlea. There had been observed patchy distribution of degenerated and almost normal nerve fiver in the modiolus with decrease in the number of the spiral ganglion cells. Furthermore their stomacks were completely empty. From the results obtained we would like to maintain that parasitogenic octavus neuropathy should be the real cause of the mass stranding of teethed whales (Odontoceti).

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Butropium Bromide (B. B) is an anticholinergic drug and usually used as an antispastic agent. In order to investigate the efficacy of B. B on aural fullness, a total of 35 patients with aural fullness (6 men and 29 women) who showed normal in general examination including otoscopic findings, pure tone audiometory and tympanogram were treated with B. B. Four mg of B. B diluted in 20ml of 20% glucose solution was injected intravenously in 5 minutes. As for age distribution in such cases, women in their thirties occupied the majority of these cases. Ten out of 35 patients stated that the fullness was diminished or gone in 30 minutes after injection .
Success rate for aural fullness was 29%. We concluded that this data suggested the close relationship between the such aural fullness and autonomic nervous system.

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