Tumoración en el colículo inferior como causa de acúfeno unilateral / Tumor at inferior colliculus causing unilateral tinnitus

Resumen La patología del sistema nervioso central, habitualmente, no provoca síntomas auditivos unilaterales, ya que la vía auditiva central está formada por una red de conexiones cruzadas entre los diferentes núcleos que la forman. Además, hay que considerar que una lesión pequeña puede extenderse a más de una estructura provocando varios déficits neurológicos debido a la proximidad de los tractos y núcleos nerviosos. Las lesiones unilaterales circunscritas en el colículo inferior son infrecuentes. No obstante, se han descrito casos en los que lesiones unilaterales de diversas etiologías en esta localización causaban síntomas auditivos. Ya que la vía auditiva central es cruzada, síntomas auditivos detectados con más frecuencia afectaban concretamente a la capacidad de localización del sonido o la comprensión verbal. Presentamos el caso de un hombre de 44 años con acúfeno unilateral derecho de larga evolución, sin otra clínica asociada quien fue diagnosticado de un tumor en el colículo inferior derecho mediante resonancia magnética cerebral. Se exponen los hallazgos clínicos y radiológicos del caso.

Abstract Central nervous system diseases usually do not cause auditory symptoms because the central auditory pathway consists on a network of crossed connections between the different nuclei that form it. In addition, we must consider that a small lesion might extend to more than one structure producing many neurologic symptoms due to the proximity of tracts and nuclei in the midbrain. Unilateral circumscribed lesions at inferior colliculus are rare. Nevertheless, lesions at this location causing auditory symptoms have been described. Because of the crossed central auditory pathway, the most commonly detected auditory symptoms specifically affected the ability to locate sound or verbal comprehension. We present the case of a 44-year-old man with a long-term monoaural right-sided tinnitus without other complaints who was diagnosed of a tumour at right inferior colliculus by neuroimaging. Clinical and radiological findings of this case are discussed.

The relationship between anxiety- and depression-like behavior and regional homogeneity of fMRI in inferior colliculus and ventrolateral orbital cortex in rats with noise-induced hearing loss / 中华行为医学与脑科学杂志

Objective:To investigate the local consistency of inferior colliculus and ventrolateral orbital cortex by resting-state functional magnetic resonance imaging (fMRI) in rats with noise induced deafness and its relationship with anxiety- and depression-like behavior.Methods:Twenty-four clean grade male four-weeks old SD rats were randomly divided into noise group and control group with 12 rats in each group.Rats in the noise group were exposed to 122 dB broadband strong noise for 2 hours to induce severe bilateral hearing loss, while rats in the control group were placed in a quiet environment. Hearing thresholds were assessed by auditory brainstem response (ABR) test. The open field test (OFT) was conducted to examine anxiety-depression related behavior, and the local consistency in the rat brain was evaluated by fMRI.SPM12 software was used to process fMRI data, and Pearson correlation analysis was conducted by SPSS 22.0 software to calculate the correlation between fMRI data and behavior.Results:The results of ABR showed that the full band hearing threshold of rats in the noise group was higher than that of rats in the control group ((85.417±6.463) dB, (20.083±8.853) dB, t=46.168, P<0.001). And compared with control group, the rats in the noise group showed obvious anxiety-depression-like behavior in the open field test, that was, low activity level.The results of OFT showed that the total distance ((39.912±5.696) m, (47.993±10.820)m, t=-2.289, P=0.032), average moving speed ((13.306±1.900)cm/s, (15.998±3.607)cm/s, t=-2.290, P=0.032) and standing times ((13.333±5.960), (23.500±7.323), t=-3.730, P=0.001) of the rats in the noise group were all lower than those in the control group. Compared with the control group, the local consistency of hypothalamus in the noise group was significantly enhanced, while the local consistency of ventrolateral orbital cortex was significantly reduced, and the abnormal neural activity was lateralized. The correlation analysis showed that the neural activity of the inferior colliculus was negatively correlated with the total distance of rats in the noise group moving in the open field( r=-0.691, P=0.013), while the neural activity of the ventrolateral orbital cortex was not significantly correlated with the anxiety-depression-like behavior in the open field. Conclusions:The neural activity of inferior colliculus is closely related to anxious-depression behavior in rats with noise-induced deafness, while the ventrolateral orbital cortex may be related with other behaviors.

Effect of Ginkgo Biloba Extract on N-Methyl-D-Aspartic Acid Receptor Subunit 2B Expression in a Salicylate-Induced Ototoxicity Model

OBJECTIVES.: Sodium salicylate (SS) is well known for its ototoxic properties that induce functional and morphological changes in the cochlea and brain. Ginkgo biloba extract (GBE) has been widely used for treatment of various neurodegenerative diseases; however, its effects on salicylate-induced ototoxicity remain unclear. Herein, we examined the effects of EGb 761 (EGb), a standard form of GBE, on the plasticity of the N-methyl-D-aspartate receptor subunit 2B (GluN2B) in the inferior colliculus (IC) following SS administration. METHODS.: Seven-week-old Sprague Dawley rats (n=24) were randomly allocated to control, SS, EGb, and EGb+SS groups. The SS group received a single intraperitoneal SS injection (350 mg/kg), the EGb group received EGb orally for 5 consecutive days (40 mg/kg), and the EGb+SS group received EGb for 5 consecutive days, followed by an SS injection. The auditory brainstem responses (ABRs) were assessed at baseline and 2 hours after SS administration. GluN2B expression was examined by Western blot and immunohistochemistry. RESULTS.: There were no significant differences in ABR threshold shifts among the groups. The expression of the GluN2B protein normalized by which of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was significantly lower in the EGb+SS group, as compared to the SS group (P=0.012). Weak and diffused GluN2B immunoreactivity was detected in the IC neural cells of the EGb+SS group, while those of the SS group exhibited strong and diffused GluN2B positivity. CONCLUSION.: EGb may play a role in regulating the GluN2B expression in the IC of salicylate-induced ototoxicity model.

Changes of Auditory Brainstem Response and Expression of Parvalbumin , Calretinin and Calbindin D-28K in the Inferior Colliculus in Rats Following Noise Exposure / 听力学及言语疾病杂志

Objective To study the possible mechanism of hearing impairment after noise exposure .Methods Adult SD rats (n=14) were monaurally exposed to a loud noise (16 kHz ,one octave band pass (116 dB SPL)) for 1-hour ,or left as non-exposed controls (n=8) .The ABR was measured before and on the 7th day following unilateral noise exposure .All the Animals were euthanased at 7th day following acoustic trauma .We used Western blots to quantify protein levels of PV ,CR and CB in the inferior colliculus .Results The auditory thresholds in 8 , 12 ,16 ,20 ,24 ,and 32 kHz of all the ears exposed to noise showed a significant increase (P<0 .001) .Compared to the sham -exposed controls ,noise-exposed animals had significantly higher levels of PV and CR and lower levels of CB in both the ipsilateral and contralateral IC than controls (P<0 .05) .Respectively ,all the noise-exposed ani-mals had higher levels of PV and CR in the ipsilateral IC than ipsilateral side (P<0 .05) .Conclusion These studies display a significant threshold shift and changes on the expressions of PV ,CR and CB in IC following acoustic trau-ma ,which may be related to noise deafness ,tinnitus and other series of auditory dysfunction .

Specific immediate early gene expression induced by high doses of salicylate in the cochlear nucleus and inferior colliculus of the rat / Expressão específica de genes precoces imediatos induzida por doses elevadas de salicilato no núcleo coclear e colículo inferior de rato

Abstract Introduction: Salicylate at high doses induces tinnitus in humans and experimental animals. However, the mechanisms and loci of action of salicylate in inducing tinnitus are still not well known. The expression of Immediate Early Genes (IEG) is traditionally associated with long-term neuronal modifications but it is still not clear how and where IEGs are activated in animal models of tinnitus. Objectives: Here we investigated the expression of c-fos and Egr-1, two IEGs, in the Dorsal Cochlear Nucleus (DCN), the Inferior Colliculus (IC), and the Posterior Ventral Cochlear Nucleus (pVCN) of rats. Methods: Rats were treated with doses known to induce tinnitus in rats (300 mg/kg i.p. daily, for 3 days), and c-fos and Egr-1 protein expressions were analyzed using western blot and immunocytochemistry. Results: After administration of salicylate, c-fos protein expression increased significantly in the DCN, pVCN and IC when assayed by western blot. Immunohistochemistry staining showed a more intense labeling of c-fos in the DCN, pVCN and IC and a significant increase in c-fos positive nuclei in the pVCN and IC. We did not detect increased Egr-1 expression in any of these areas. Conclusion: Our data show that a high dose of salicylate activates neurons in the DCN, pVCN and IC. The expression of these genes by high doses of salicylate strongly suggests that plastic changes in these areas are involved in the genesis of tinnitus.

Resumo Introdução: Salicilato em doses elevadas induz zumbido nos seres humanos e em animais experimentais. No entanto, os mecanismos e loci de ação do salicilato na indução de zumbido ainda não são bem conhecidos. A expressão dos genes precoces imediatos (GPIs) está tradicionalmente associada a alterações neuronais em longo prazo, mas ainda não está claro como e onde os GPIs são ativados em modelos animais de zumbido. Objetivos: No presente estudo investigamos a expressão de c-fos e Egr-1, dois GPIs, no núcleo coclear dorsal (NCD), colículo inferior (CI) e núcleo coclear ventral posterior (NCVp) de ratos. Métodos: Os ratos foram tratados com doses que, conhecidamente, induzem zumbido em ratos (300 mg/kg IP/dia, por três dias) e as expressões das proteínas c-fos e Egr-1 foram analisadas por meio de Western blot e imunoistoquímica. Resultados: Após a administração de salicilato, a expressão da proteína c-fos aumentou significativamente no NCD, NCVp e CI, quando analisados por Western blot. A coloração imunoistoquímica mostrou uma marcação mais intensa de c-fos no NCD, NCVp e CI e um aumento significativo de núcleos positivos de c-fos no NCVp e CI. Não detectamos aumento da expressão de Egr-1 em qualquer dessas áreas. Conclusão: Nossos dados mostram que uma dose alta de salicilato ativa neurônios no NCD, NCVp e CI. A expressão desses genes por doses altas de salicilato sugere que as alterações plásticas nessas áreas estão envolvidas na gênese do zumbido.

Expression of Growth Associated Protein 43 in Inferior Colliculus of Rats at Different Times after Impulse Noise Exposur / 听力学及言语疾病杂志

Objective To investigate the effect of impulse noise expose on the expression of growth associated protein 43(Gap-43) in inferior colliculus in rat.Methods SPF grade Male SD rats were randomly divided into 5 groups.The normal control group received noise exposure.The model groups received an averange impulse noise exposure of 156 dB SPL with a pulse duration of 0.23 ms, once for 6 s, for 50 times.Auditory brainstem responses (ABRs) were measured before and 3,7,14, and 28 d after noise exposure with tone pips of 2,4,8,16, and 32 kHz, from 20 to 110 dB SPL.Bilateral inferior colliculus of rats in the model groups was collected and treated by immunohistochemical staining.Gap-43 expression of rats in different groups was measured by determining the gray value of inferior immunohistochemical images.Results After noise exposure, ABRs threshold in the model groups were significantly higher than those of in the normal group (P<0.05 or P<0.01).ABRs threshold at 14 and 28 days after noise exposure were significantly lower than 3 days after impulse exposure (P<0.05).Expression of Gap-43 in inferior colliculus was significantly up-regulated in the noise exposed groups compared with the normal group (P<0.05 or P<0.01).Expression of Gap-43 was significantly down-regulated 28 days after noise expose compared with 3 days after noise expose(P<0.05).Conclusion Impulse noise exposure leads to significant elevation of ABR thresholds and up-regulation of Gap-43 expression in inferior colliculus.Impulse noise exposure may induce auditory cortex prominent remodeling.

The Expression of EphA4 in Inferior Colliculus Involves in the Pathology of Salicylate Induced Tinnitus in Rat / 听力学及言语疾病杂志

Objective To investigate the influences of sodium salicylate on the auditory brainstem response (ABR)and expression of EphA4mRNA in rat inferior colliculus and its effects on salicylate ototoxicity.Methods A total of 30 healthy SPF rats were randomly divided into five groups:the control group (without any treatment),S7 (i.m.injection of sodium salicylate,175mg/kg,twice daily for 7 days),S14(the same method as S7,twice daily for 14 days),S14+R14(the same method as S14,twice daily for 14 days and recovered for 14 days),and S14+R28(the same method as S14,twice daily for 14 days and recovered for 28 days).After the ABR assessment,rats were sacri-ficed after deep anesthesia and the inferior colliculus tissues were dissected.Real-time PCR was used to detect the expression of EphA4mRNA.Results Compared with the control group,ABR thresholds in the S7 group and S14 group were increased significantly (P0.05).The inferior colliculus EphA4mRNA expression level of S7 group was signifi-cantly decreased than the control group (P0.05).Conclusion Long term injection of sodium salicylate can cause changes in the inferior colliculus of EphA4mRNA which are related closely with synaptic plasticity.It may lead the alteration of the inferior colliculus synaptic plasticity,which is associated with the changes of the hearing failure and the tinni-tus behavior.This indicates that EphA4 which is considered as a related protein in the inferior colliculus may play an important role in the pathology of tinnitus.

The distribution of calbindin-D28k, parvalbumin, and calretinin immunoreactivity in the inferior colliculus of circling mouse / 대한해부학회지

The circling mice with tmie gene mutation are known as an animal deafness model, which showed hyperactive circling movement. Recently, the reinvestigation of circling mouse was performed to check the inner ear pathology as a main lesion of early hearing loss. In this trial, the inner ear organs were not so damaged to cause the hearing deficit of circling (cir/cir) mouse at 18 postnatal day (P18) though auditory brainstem response data indicated hearing loss of cir/cir mice at P18. Thus, another mechanism may be correlated with the early hearing loss of cir/cir mice at P18. Hearing loss in the early life can disrupt the ascending and descending information to inferior colliculus (IC) as integration site. There were many reports that hearing loss could result in the changes in Ca²⁺ concentration by either cochlear ablation or genetic defect. However, little was known to be reported about the correlation between the pathology of IC and Ca²⁺ changes in circling mice. Therefore, the present study investigated the distribution of calcium-binding proteins (CaBPs), calbindin-D28k, parvalbumin, and calretinin immunoreactivity (IR) in the IC to compare among wild-type (+/+), heterozygous (+/cir), and homozygous (cir/cir) mice by immunohistochemistry. The decreases of CaBPs IR in cir/cir were statistically significant in the neurons as well as neuropil of IC. Thus, this study proposed overall distributional alteration of CaBPs IR in the IC caused by early hearing defect and might be helpful to elucidate the pathology of central auditory disorder related with Ca²⁺ metabolism.

Analysis of inferior colliculus region typical proteins in auditory pathway / 中国耳鼻咽喉头颈外科

OBJECTIVE To study the proteome of inferior colliculus and determinate the region-typical proteins which may be the candidate cause of the Central Auditory Processing Disorders. METHODS The telencephalon was taken as reference, and then identified and quantified the proteome of IC of adult rats with iTRAQ. Those with higher abundance in inferior colliculus than the other three regions were considered as IC-Region typical proteins,which may lead to functional specializations. RESULTS We identified 1937 cytomembrane proteins in total, among which there are 53 IC-Region typical proteins, which may lead to functional specializations of inferior colliculus.We used GO and KEGG pathway to analyze these proteins and then found that these proteins mainly take part in the regulation of neurons development and information integrations. CONCLUSION Our quantitative comparison of inferior colliculus has revealed two candidate proteins, including CaMKII and SV2A, which may play important roles in maintaining the balance of excitatory and inhibitory transmitters release. These proteins may be the candidate proteins for Central Auditory Processing Disorders.

Reduced Gray Matter Volume of Auditory Cortical and Subcortical Areas in Congenitally Deaf Adolescents: A Voxel-Based Morphometric Study

PURPOSE: Several morphometric studies have been performed to investigate brain abnormalities in congenitally deaf people. But no report exists concerning structural brain abnormalities in congenitally deaf adolescents. We evaluated the regional volume changes in gray matter (GM) using voxel-based morphometry (VBM) in congenitally deaf adolescents. MATERIALS AND METHODS: A VBM8 methodology was applied to the T1-weighted magnetic resonance imaging (MRI) scans of eight congenitally deaf adolescents (mean age, 15.6 years) and nine adolescents with normal hearing. All MRI scans were normalized to a template and then segmented, modulated, and smoothed. Smoothed GM data were tested statistically using analysis of covariance (controlled for age, gender, and intracranial cavity volume). RESULTS: The mean values of age, gender, total volumes of GM, and total intracranial volume did not differ between the two groups. In the auditory centers, the left anterior Heschl's gyrus and both inferior colliculi showed decreased regional GM volume in the congenitally deaf adolescents. The GM volumes of the lingual gyri, nuclei accumbens, and left posterior thalamic reticular nucleus in the midbrain were also decreased. CONCLUSIONS: The results of the present study suggest that early deprivation of auditory stimulation in congenitally deaf adolescents might have caused significant underdevelopment of the auditory cortex (left Heschl's gyrus), subcortical auditory structures (inferior colliculi), auditory gain controllers (nucleus accumbens and thalamic reticular nucleus), and multisensory integration areas (inferior colliculi and lingual gyri). These defects might be related to the absence of general auditory perception, the auditory gating system of thalamocortical transmission, and failure in the maturation of the auditory-to-limbic connection and the auditorysomatosensory-visual interconnection.

The Expression of GAP-43 in Cochlear Nucleus and Inferior Colliculus after Unilateral Cochlear Damage in Rats / 听力学及言语疾病杂志

Objective To study the changes of the expression of growth associated protein -43(GAP 43) in cochlear nucleus and the inferior colliculus (IC) in rats after unilateral cochlear damage at different time points after surgery ,and explore the remodeling and repair process of synapse in brainstem auditory center of rats after auditory deprivation .Methods Thirty rats were randomly divided into six groups :the 3 ,7 ,15 ,30 ,60 days group (with u-nilateral cochlea damage) and the control group (without cochlea damage) with 5 rats in each group .The immuno-histochemical SP method was used to detect the expression of GAP -43 in cochlear nucleus and inferior colliculus at different time points after cochlea damaged in the control group .Results After the unilateral cochlear ear was dam-aged at 3 ,7 ,15 days ,GAP -43 in operation side cochlear nucleus were expressed and the expression level signifi-cantly increased compared with normal control group .After 30 days postoperatively ,GAP - 43 expression level decreased ,but it was still higher than normal control group .After 60 days postoperatively ,GAP - 43 expression level was slightly higher than that of normal control group .After 3 days postoperatively ,GAP - 43 expression level was higher than normal control group .After 7 ,15 days postoperatively ,expression levels were increased .After 30 , 60 days postoperatively ,the expressions gradually decreased ,but still higher than the normal control group .Conclusion After unilateral cochlea damaged ,GAP - 43 was expressed an obvious dynamic change process in cochlear nucleus and infe-rior colliculus .It may reflect the axonal regeneration and synaptic plasticity after hearing loss in brainstem auditory neurons .

Effects of Long Term Injection of Sodium Salicylate on the ABR and Expression of GAD67 in Rat Inferior Colliculus / 听力学及言语疾病杂志

Objective To observe the effects of long term injection sodium salicylate on the auditory brain-stem response(ABR)and expression of glutamic acid decarboxylase -67(GAD67) in rat inferior colliculus .Methods Eighteen healthy Wistar rats were randomly divided into three groups :the sodium salicylate group (intramuscular injection of 10% sodium salicylate ,175 mg/kg ,twice daliy for 28 days) ,the saline group (intramuscular injection with saline on same does at the same time) ,the control group (without any treatment) .The rats received ABR after modeling ,then were decapitated and inferior colliculus tissues were stripped .Western blot was used to study the dif-ferent expression of GAD67 protein levels in the three groups .Results Compared with the saline group and control group ,ABR thresholds of the sodium salicylate group were significantly elevated and latency of wave Ⅲ was aslo sig-nificantly prolonged(P0 .05) .The inferior colliculus GAD67 protein expression level of sodium salicylate group was significantly higher than the saline group and control group(P0 .05) .Conclusion Long term injection of sodium salicylate can cause a change in the inferior colliculus of GAD67 protein expression and the up regulation of GAD67 expression may occur as a com-pensatory response to increase inhibiting effect .The change of GAD67 protein expression is likely as a compensatory and regulatory mechanisms for sodium salicylate ototoxicity .

Effect of propofol on the first spike latency-amplitude curve of rat inferior colliculus neurons / 重庆医学

Objective To evaluate effect of propofol on the first spike latency-amplitude curve of rat inferior colliculus neurons and to find out mechanisms that propofol leds to the disappearance of auditory nerve electrophysiological .Methods 43 healthy specefic pathogen free(SPF) grade sprague dawley(SD) rats(weighing 200-250 g) were used to established wakeful animal models by ventilating with animal respirator after infusing vecuronium .A microelectrode was penetrated in the inferior colliculus (IC) ,and then research first spike latency-amplitude(FSL-A) using a Tucker-Davis Technologies System 3(TDT3) before and after intraper-itoneal injection of propofol 100 mg/kg of each 10 minutes interval .Results CFs ranging from 2 .5 to 44 kHz .An acoustic response of neurons showed offset response ,the remaining 42 neurons showed onset response .r2 of FSL-A curve equations are significant difference between administered propofol before and after 10 minutes(P<0 .05) ,all of them are larger than 0 .95(P<0 .05) .FSL-A curve after administration can shift the lower curve and coincident with the previous administration in the same rat .Conclusion Propofol affect auditory information transmission by convert localization of FSL-A curve of rat inferior colliculus neurons ,but does not change the meaning of the information encoded .

Effects of chronic administration of efavirenz on the chromatophilic substance of the intracranial auditory relay centres of adult Wistar rats / Efectos de la administración crónica de efavirenz sobre la sustancia cromatofílica de los centros de relevo auditivos intracraneales de ratas Wistar adultas

The effects of chronic administration of efavirenz commonly used as part of highly active antiretroviral therapy (HAART) for the treatment of Human Immunodeficiency Virus (HIV) type-1 therapy on the chromatophilic substance of the intracranial auditory relay centre namely the inferior colliculus and medial geniculate body of adult wistar rats were carefully studied. The rats of both sexes (n=20), with an average weight of 200g were randomly assigned into treatment (n=10) and control (n=10) groups. The rats in the treatment group received 600 mg/70kg body weight of efavirenz dissolved in distilled water daily for 30 days through the orogastric tube. The control group received equal volume of distilled water daily for 30 days through the same route. The rats were fed with grower's mash obtained from Edo Feeds and Flour Mill Limited, Ewu, Edo state, Nigeria and given water liberally. The rats were sacrificed by cervical dislocation method on the thirty-first day of the experiment. The inferior colliculus and medial geniculate body were carefully dissected out and quickly fixed in 10 percent formal saline for histological study. The histological findings indicated that the treated sections of the inferior colliculus and medial geniculate body showed that the chromatophilics substances were less intensely stained as compared to the control. The parenchyme was vacuolated and with evidence of hypertrophy and more spaces between the axonal mesh around the sparsely distributed neurons as compared to the control group. The treated section of the inferior colliculus showed neurons with faintly stained chromatophilics substances in large, medium and small sized neurons while that of the medial geniculate body showed less intense and enlarge chromatophilics substances with some vacuolations. Chronic administration of efavirenz may therefore have an adverse effect on the chromatophilics substances of the inferior colliculus and medial geniculate body of adult wistar rats...

Fueron estudiados los efectos de la administración crónica del efavirenz, comúnmente utilizado como parte del tratamiento antirretroviral de gran actividad para el VIH tipo 1, sobre la sustancia cromatofílica del centro de relevo auditivo intracraneal, el colículo inferior y cuerpo geniculado medial, en ratas Wistar adultas. Ratas de ambos sexos (n = 20), con un peso promedio de 200g fueron asignadas aleatoriamente a tratamiento (n = 10) y control (n = 10). Las ratas del grupo tratado recibieron 600mg/70kg peso corporal de efavirenz disuelto en agua destilada durante 30 días a través de sonda orogástrica. El grupo de control recibió un volumen igual de agua destilada durante 30 días por la misma vía. Las ratas fueron alimentadas con puré agricultor obtenido de Edo Feeds and Flour Mill Limited, Ewu, estado de Edo, Nigeria y agua ad-libitum. Las ratas se sacrificaron por dislocación cervical el día 31. El colículo inferior y el cuerpo geniculado medial fueron disecados cuidadosamente y se fijaron en solución de formalina salina al 10 por ciento. Los hallazgos histológicos indicaron que en las secciones tratadas del colículo inferior y el cuerpo geniculado medial la sustancia cromatofílica fue menos intensamente teñidas en comparación con el control. El parénquima se vacuoló, con evidencia de hipertrofia y más espacios entre la red axonal alrededor de neuronas escasamente distribuidas en comparación con el grupo control. La sección tratada del colículo inferior mostró neuronas con sustancia cromatofílica débilmente teñida en las neuronas de tamaño grande, mediano y pequeño, mientras que las del cuerpo geniculado medial mostraron sustancia cromatofílica menos intensa, con algunas vacuolaciones amplias. La administración crónica de efavirenz puede tener un efecto adverso sobre las sustancias cromatofílica del colículo inferior y del cuerpo geniculado medial de ratas Wistar adultas. Se recomienda realizar estudios adicionales...

Binaural Electric-Acoustic Interactions Recorded from the Inferior Colliculus of Guinea Pigs: The Effect of Masking Observed in the Central Nucleus of the Inferior Colliculus

OBJECTIVES: To investigate the electric-acoustic interactions within the inferior colliculus of guinea pigs and to observe how central masking appears in invasive neural recordings of the inferior colliculus (IC). METHODS: A platinum-iridium wire was inserted to scala tympani through cochleostomy with a depth no greater than 1 mm for intracochlear stimulation of electric pulse train. A 5 mm 100 microm, single-shank, thin-film, penetrating recording probe was inserted perpendicularly to the surface of the IC in the coronal plane at an angle of 30-40degrees off the parasagittal plane with a depth of 2.0-2.5 mm. The peripheral and central masking effects were compared using electric pulse trains to the left ear and acoustic noise to the left ear (ipsilateral) and to the right ear (contralateral). Binaural acoustic stimuli were presented with different time delays and compared with combined electric and acoustic stimuli. The averaged evoked potentials and total spike numbers were measured using thin-film electrodes inserted into the central nucleus of the IC. RESULTS: Ipsilateral noise had more obvious effects on the electric response than did contralateral noise. Contralateral noise decreased slightly the response amplitude to the electric pulse train stimuli. Immediately after the onset of acoustic noise, the response pattern changed transiently with shorter response intervals. The effects of contralateral noise were evident at the beginning of the continuous noise. The total spike number decreased when the binaural stimuli reached the IC most simultaneously. CONCLUSION: These results suggest that central masking is quite different from peripheral masking and occurs within the binaural auditory system, and this study showed that the effect of masking could be observed in the IC recording. These effects are more evident and consistent with the psychophysical data from spike number analyses than with the previously reported gross potential data.

GluR2 expression in the developing rat inferior colliculus and the relationship with development of synapse / 临床耳鼻咽喉头颈外科杂志

Objective:To observe the GluR2 expression in rat inferior colliculus (IC) in different developmental stages , and to investigate its developmental change and relationship with the synapse development.Method: The expression of GluR2 and synaptophysin(SYP) in IC were detected by double immunofluorescence method.Result:①All sorts of neurons in IC expressed GluR2 in every postnatal groups, and the GluR2 expression in P6w groups was higher than that in other groups .②The expression of GluR2 were different in different subnucleus of IC.③All sorts of neurons in IC expressed SYP in every postnatal groups, and the SYP expression in P6w groups was higher than others. ④The expressions of GluR2 consistented with the expression of SYP in IC.Conclusion:The developmental changes of GluR2 and SYP expression in the rat IC may be involved in the development and plasticity of auditory center.

Involvement of GABAergic mechanisms of the dorsal periaqueductal gray and inferior colliculus on unconditioned fear

The fact that the dorsal periaqueductal gray (dPAG) and inferior colliculus (IC), together with superior colliculus, medial hypothalamus and amygdala, constitute the brain aversion system has been well-established. Stepwise increases in the intensity of electrical stimulation of dPAG or IC cause freezing and escape responses, which are followed by a freezing behavior that lasts after the interruption of the stimulation. Freezing and escape are unconditioned defensive behaviors derived from the stimulation of the output centers for the defense reaction, whereas the post-stimulation freezing is the behavioral counterpart of the processing of aversive information. Although GABA-A mechanisms of the midbrain tectum exert a tonic inhibitory influence on the neural substrates of unconditioned fear, their influence on the processing of aversive information is not completely understood. Thus, the present study examines the effects of injections of the GABA-A receptor agonist muscimol (1 and 2 nmol/0.2 µL) or the glutamic acid decarboxylase blocker semicarbazide (5 and 7.5 µg/0.2 µL) into dPAG or IC of Wistar rats on freezing and escape thresholds determined by electrical stimulation of these same structures and on post-stimulation freezing. Intra-dPAG injections of muscimol increased and semicarbazide decreased the freezing and escape thresholds of electrical stimulation of the dPAG. Only semicarbazide enhanced the dPAG post-stimulation freezing. Intra-IC injections of muscimol significantly increased aversive thresholds, while having no effect on IC post-stimulation freezing. Intra-IC injections of semicarbazide had no significant effects. These findings suggest that GABAergic mechanisms are important regulators of the expression of unconditioned fear in dPAG and IC, whereas only in dPAG GABA appears to play a role on the sensory gating towards aversive information during post-stimulation freezing.

Effect of Noise on the Auditory Center / 第二军医大学学报

Adult guinea pigs with normal Preyer's reflexs were used in this experiment and were divided into three groups according to the intensity of noise and exposure time. Auditory brainstem evoked response was recorded before and after exposure to noise. Clicks were presented monaurally at a rate of high (50 Hz) as well as low (10 Hz). The superior olive and inferior colliculus were observed under the electron microscope after the guinea pigs were exposured to 110dB noise for 30 min. The average shift of wave Ⅳ amplitude-intensity function curve was more than that of wave I after exposure to intensive noise. The difference value of wave Ⅴ latency from low (10 Hz) to high (50 Hz) stimulus click rate decreased and was negatively co related with the exposure time. Ⅰ-Ⅴ, Ⅲ -Ⅴ and Ⅳ-Ⅴ interpeak latencies were shorter after exposure to noise. The mitochondria and neurilemma swelling were found in the superior olive and inferior colliculus after exposure. Some mechanisms of the changes of auditory center were discussed in this paper.

Auditory Center Affected by Chronic Noise Exposure / 第二军医大学学报

In order to study the effect of chronic noise exposure on auditory center, seven guinea pigs were .exposured to 105 dB A noise 8h daily for 45 d. Then the animals were killed by decapitation. The superior olive and inferior colliculus were taken immediately to make the samples of electron microscope. The mitochondria swelling, membrane rupture, cristae breaking, ballooning degeneration were found. The rough surfaced endoplasmic reticulum was swollen and expanded. The lysosome and secondary lysosome were increased. The cell interstitial edema and synaptic besicle decrease were observed. The nuclear chromatid was decreased and nucleolus was kept to the side. The laminae of neurilemma of nerve fibers were dissociated, swollen and broken. The results indicate that the ultrastructure, neural cells and fibers in the auditory center are damaged by chronic noise exposure and most of these damages are irreversible.

THE NON-AUDITORIAL AFFERENTS OF THE INFERIOR COLLICULUS IN THE RAT——WGA-HRP METHOD / 解剖学报

WGA-HRP was injected into the inferior colliculus in the rat in order to study the non-auditorial afferents of the inferior colliculus. In the diencephalon and truncus encephali, retrograde labeling was observed in many non-auditorial regions: bilateral (with contralateral predominance) cuneate nucleus, gracile nucleus, nucleus of spinal tract of trigeminal nerve, nucleus medullae oblongatae centralis dorsalis; bilateral (with homolateral predominance) locus ceruleus, nucleus reticularis pontis oralis, laterodorsal tegmental nucleus, substantia nigra, sub-parafascicular nucleus, perifornical nucleus; bilateral medial parabrachial nucleus, deep tegmental nucleus of midbrain, lateral hypothalamic area; homolateral deep layer of superior colliculus, zona incerta; contralateral nucleus of solitary tract; and posteromedian septum, central tegmental nucleus, dorsal nucleus of the raphe. The afferent neurons from cuneate nucleus, gracile nucleus, nucleus of spinal tract of trigeminal nerve, nucleus of solitary tract mainly located below the level of obex. The results mentioned above suggested that the inferior colliculus is not only an auditorial relay nucleus, but also a complex body which is of different functions.