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.

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.

Bilateral Hearing Loss in Wernicke Encephalopathy

Wernicke encephalopathy is a syndrome caused by thiamine deficiency whose three typical symptoms are ophthalomoplegia, ataxia, and confusion. There are also rare reports of bilateral hearing loss, which can be caused by damage to the bilateral inferior colliculus or thalamic lesions, or by energy failure of the cochlea. This case suggests that thiamine should be administered based on the possibility of Wernicke encephalopathy occurring in malnourished or alcoholic patients with sudden bilateral hearing loss.

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.

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.

Effects of electrical stimulation at acupoints in the distribution area of auricular vagus nerve combined with sound masking method on auditory brainstem response and neurotransmitters of inferior colliculus in rats of tinnitus / 中国针灸

<p><b>OBJECTIVE</b>To explore the effects of electrical stimulation at acupoints in the distribution area of auricular vagus nerve combined with sound masking on auditory brainstem response (ABR) and contents of neurotransmitters of γ-aminobutyric acid (γ-GABA), 5-hydroxytryptamine (5-HT) and acetyl choline (Ach) in inferior colliculus of tinnitus rats.</p><p><b>METHODS</b>Twenty-four male adult SD rats were randomized into a control group, a model group, a 7-d treatment group and a 15-d treatment group. Except the control group, rats in the remaining groups were treated with intraperitoneal injection of 10% salicylate sodium at a dose of 350 mg/kg to establish tinnitus model. Rats in the control group were treated with injection of 0.9% NaCl. Rats in the 7-d treatment group and 15-d treatment group were treated with electrical stimulation at "Shenmen (TF₄)" and "Yidan (CO₁₁)" in the distribution area of auricular vagus nerve combined with sound masking, once a day, for 7 days and 15 days. The SigGenRP software of TDT system was applied to provide voice for single ear and collect the signal, and the voice threshold of ABR was tested. The levels of γ-GABA, 5-HT and Ach in inferior colliculus of rats were detected by enzyme linked immunosorbent assay (ELISA) and compared.</p><p><b>RESULTS</b>Compared with the model group, the threshold values of ABR in 12 kHz and 16 kHz voice stimulation in the 7-d treatment group were significantly lower all P < 0.05); the threshold values of ABR from 4 kHz to 28 kHz voice stimulation in the 15-d treatment group were signally reduced (P < 0.05, P < 0.01), which was more significant than those in the 7-d treatment group. The level of γ-GABA in the model group was significantly lower than that in the control group (P < 0.05), and that in the 15-d treatment group was apparently higher than that in the model group (P < 0.05). The level of 5-HT in the model group was markedly higher than that in the control group (P < 0.05), and that in the 7-d treatment group was lower than that in the model group (P < 0.05), while that in the 15-d treatment group was apparently higher than that in the model group (P < 0.05). The level of Ach in the model group was obviously; lower than that in the control group (P < 0.05), and that in the 7-d treatment group was higher than that in the model group (P < 0.05).</p><p><b>CONCLUSION</b>Electrical stimulation at auricular vagus nerve combined with sound masking) could regulate the threshold of ABR, especially in the 15-d treatment group. This may be ascribed to modulating the levels of neurotransmitter of γ-GABA, 5-HT and Ach in inferior colliculus.</p>

Response characteristics of neurons to tone in dorsal nucleus of the lateral lemniscus of the mouse / 生理学报

The dorsal nucleus of lateral lemniscus (DNLL) is a nucleus in the auditory ascending pathway, and casts inhibitory efferent projections to the inferior colliculus. Studies on the DNLL are less than studies on the auditory brain stem and inferior colliculus. To date, there is no information about response characteristics of neurons in DNLL of albino mouse. Under free field conditions, we used extracellular single unit recording to study the acoustic signal characteristics of DNLL neurons in Kunming mice (Mus musculus). Transient (36%) and ongoing (64%) firing patterns were found in 96 DNLL neurons. Neurons with different firing patterns have significant differences in characteristic frequency and minimal threshold. We recorded frequency tuning curves (FTCs) of 87 DNLL neurons. All of the FTCs exhibit an open "V" shape. There is no significant difference in FTCs between transient and ongoing neurons, but among the ongoing neurons, the FTCs of sustained neurons are sharper than those of onset plus sustained neurons and pauser neurons. Our results showed that the characteristic frequency of DNLL neurons of mice was not correlated with depth, supporting the view that the DNLL of mouse has no frequency topological organization through dorsal-ventral plane, which is different from cats and some other animals. Furthermore, by using rate-intensity function (RIF) analysis the mouse DNLL neurons can be classified as monotonic (60%), saturated (31%) and non-monotonic (8%) types. Each RIF type includes transient and ongoing firing patterns. Dynamic range of the transient firing pattern is smaller than that of ongoing firing ones (P < 0.01), suggesting that the inhibitory inputs may underlie the formation of transient firing pattern. Multiple firing patterns and intensity coding of DNLL neurons may derive from the projections from multiple auditory nuclei, and play different roles in auditory information processing.

The expression of Calbindin and Parvalbumin in auditory pathway of kit gene mutated C57BL/6J mouse / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To observe the expressions of Calbindin(CB) and Parvalbumin (PV), the two calcium-binding protein, in auditory pathway in mice of wild type C57BL/6J and kit⁺/kitW⁻ ²Bao, a kit gene mutant.</p><p><b>METHODS</b>Six mutated kit gene kit⁺/kitW⁻ ²Bao mice and 6 wild type C57BL/6J (B6) mice were anaesthetized i. p. with chloral hydrate. After the mice were fixed by heart perfusion, the brains were removed and coronal sections were cut with a freezing microtome.</p><p><b>RESULTS</b>We found that wild type mice had significant expressions of PV on ventral cochlear nucleus, anterior part (AVCN), ventral cochlear nucleus, posterior part (PVCN), inferior colliculus (IC) and auditory cortex (AC). CB was expressed in wild type mice on PVCN and nucleus of the trapezoid body (Tz). The mutant of kit gene induced the less expression of PV on PVCN, IC and AC (P < 0.01), but increased the expression of Tz (P < 0.01). CB could not be observed on PVCN in mutant mice, and the expression of AC was increased( P < 0.01).</p><p><b>CONCLUSION</b>CB and PV has differential expression level in auditory pathway. Since mutated kit gene can affect expression of PV on PVCN, IC, Tz and AC, as well as CB on PVCN and AC, it suggests that the mutation of kit gene can affect the advanced function of central nervous system in auditory pathway.</p>

In vitro whole-cell patch clamp recordings of neurons in subnuclei of mouse inferior colliculus / 生理学报

The inferior colliculus (IC) is a pivot along the central auditory pathway. Using infrared visual whole-cell patch clamp recording technique, we investigated the electrophysiological properties of IC subnuclei neurons. Recordings were made from 88 neurons, including 21 neurons from the dorsal cortex of the IC (ICd), 43 neurons from the central nucleus of the IC (ICc) and 24 neurons from the external cortex of the IC (ICx). Based on the responses to positive current injection, three firing patterns, i.e., onset (6.8%, n = 6), adapting (39.8%, n = 35) and sustained (53.4%, n = 47) patterns, were identified. The hyperpolarization-activated inward current (Ih) could be recorded in half of the neurons (49/88). The sustained pattern occurred in more than half of ICd and ICc neurons (61.9% and 67.4%), while the adapting pattern occurred in majority of ICx neurons (75%). Action potential (AP) threshold and time constant also showed significant differences across neurons from the ICd, the ICc and the ICx. Our results indicate that IC neurons are different in electrophysiological properties across the subnuclei. The variance of the responses may be related to the distinct types of neurons as well as the received projections, which is implicated in the distinct roles of IC neurons in central auditory processing.

Correlation of diffusion tensor imaging between the cerebral cortex and speech discrimination in presbycusis / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigate the relationship between pure-tone average (PTA), the fractional anisotropy (FA) of the auditory pathway, cognitive cortex and auditory cortex in presbycusis.@*METHOD@#Twenty-five elderly subjects with presbycusis were participated in the study. PTA, speech discrimination abilities were evaluated in each subject. Diffusion tensor imaging (DTI) was applied to access the FA of the IC, the superior frontal gyrus and the Heschl's gyrus. Compare the difference between two sides of the values of FA in the three areas. Bivariate correlation analysis was performed to evaluate the effects of PTA and FA of the inferior colliculus (IC), the superior frontal gyrus and the Heschl's gyrus on speech discrimination abilities.@*RESULT@#There were no significant differences between the left and right side of the inferior colliculus (P > 0.05). Higher FA values were recorded at the left side of the Heschl's gyrus and the superior frontal gyrus (P < 0.05). Both PTA and the FA of the superior frontal gyrus have a negative association with speech discrimination abilities (P < 0.01, P < 0.05), while the FA of the Heschl's gyrus has a positive association with speech discrimination abilities (P < 0.05).@*CONCLUSION@#Our findings indicated that the speech discrimination abilities of the elderly is not only related to the peripheral auditory function, but also to the central auditory and cognitive function.

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.

Infection of the heart of Pimelodus ornatus (Teleostei, Pimelodidae), by Myxobolus sp. (Myxozoa, Myxobolidae) / Infecção do tecido cardíaco de Pimelodus ornatus (Teleostei, Pimelodidae), por Myxobolus sp. (Myxozoa, Myxobolidae)

The phylum Myxozoa Grassé, 1970, consists of a heterogenous group of around 50 genera that are worldwide disseminated in a wide variety of aquatic media. In the present study, 43 specimens of Pimelodus ornatus were collected from an adjacent area to the Cachoeira do Arari municipality on Marajó Island, in the Brazilian state of Pará, in 2013. Macroscopic analysis showed the presence of whitened plasmodia located in the cardiac muscle and also in the region between the bulbus arteriosus and atrium cordis. Microscopic analysis on the parasitized tissues revealed spores that were typically piriform, with the anterior portion slightly narrower than the posterior end. The spore valves were symmetrical. The present species is placed in the genus Myxobolus Butschli, 1882, because of the presence of a pair of equal polar capsules in each spore. The prevalence of parasitism observed was 13.9% (6/43). This research note reports the first occurrence of Myxobolus as a parasite of the heart in the teleostean fish P. ornatus in the Amazon region and confirms the occurrence of secondary myocarditis in this fish, caused by parasitism by Myxobolus sp. The rarity of this parasitic species of Myxobolus at this tissue site, associated with other spore morphology characteristics in the fish, suggests that it is an undescribed species.

O filo Myxozoa Grassé, 1970, consiste em um grupo heterogêneo de cerca de 50 gêneros que são disseminados em todo o mundo em uma grande variedade de meios aquáticos. No presente estudo, quarenta e três espécimes de Pimelodus ornatus foram coletados a partir de uma área adjacente à cidade de Cachoeira do Arari, na Ilha do Marajó, no Estado do Pará, em 2013. À análise macroscópica verificou-se a presença de plasmódios esbranquiçados, localizados no músculo cardíaco e também na região entre o bulbus arteriosus e o atrium cordis. A análise microscópica dos tecidos parasitados revelou esporos que eram tipicamente piriformes, com a porção anterior um pouco mais estreita do que a extremidade posterior, sendo suas válvulas simétricas. A prevalência do parasitismo observada foi de 13,9% (6/43). Esta nota de pesquisa relata a primeira ocorrência de Myxobolus como um parasita do coração no peixe teleósteo P. ornatus, na Região Amazônica e, confirma a ocorrência de miocardite secundária causada por esse parasitismo. A raridade da ocorrência de Myxobolus sp. neste tecido, associado a outras características morfológicas dos esporos no peixe, sugere que é uma espécie não descrita.

Encuesta nacional de ceguera y deficiencia visual evitables en Honduras / National survey of blindness and avoidable visual impairment in Honduras

OBJETIVO: Determinar la prevalencia de ceguera y deficiencia visual en Honduras, sus causas y la respuesta que los servicios de salud están dando a la creciente demanda. MÉTODOS: Estudio poblacional transversal realizado entre junio y diciembre de 2013 mediante la metodología estándar de evaluación rápida de ceguera evitable. Se realizó un muestreo aleatorio en 63 conglomerados de 50 personas de 50 años o más, representativo de todo el país. Se evaluó la agudeza visual (AV) mediante una cartilla de Snellen y el estado del cristalino y del polo posterior por oftalmoscopía directa. Se calculó la cobertura de cirugía de catarata y se evaluó su calidad, las causas de tener AV < 20/60 y las barreras para acceder al tratamiento quirúrgico. RESULTADOS: Se examinaron 2 999 personas (95,2% del total previsto). La prevalencia de ceguera fue de 1,9% (intervalo de confianza de 95%: 1,4-2,4%) y 82,2% de esos casos era evitable. La catarata no operada fue la causa principal de ceguera (59,2%), seguida del glaucoma (21,1%). Los errores de refracción no corregidos fueron la principal causa de deficiencia visual, tanto severa (19,7%) como moderada (58,6%). La cobertura de cirugía de catarata fue de 75,2%. De los ojos operados de catarata, 62,5% alcanzó una AV ≥ 20/60 con la corrección disponible. Las principales barreras para someterse a la cirugía de catarata fueron el costo (27,7%) y la falta de disponibilidad o de acceso geográfico al tratamiento (24,6%). CONCLUSIONES: La prevalencia de ceguera y deficiencia visual en Honduras es similar a la de otros países latinoamericanos. Mejorar la capacidad resolutiva de los servicios oftalmológicos, especialmente de cirugía de catarata, desarrollar los servicios ópticos y la atención ocular incorporada en la atención primaria en salud, podrían resolver el 67% de los casos de ceguera.

OBJECTIVES: To determine the prevalence of blindness and visual impairment in Honduras, its causes and the response by the health services to growing demand. METHODS: A cross-sectional population study was conducted between June and December 2013 using the standard methodology of the Rapid Assessment of Avoidable Blindness. A random sample survey was done in 63 clusters of 50 individuals aged ≥ 50, representative of the country as a whole. Visual acuity (VA) was assessed using a Snellen eye chart, and the condition of the lens and posterior pole was examined by direct ophthalmoscopy. Cataract surgical coverage was calculated and an assessment made of its quality, the causes of VA < 20/60 and the barriers to accessing surgical treatment. RESULTS: A total of 2 999 people were examined (95.2% of the forecast total). Blindness prevalence was 1.9% (confidence interval of 95%: 1.4-2.4%) and 82.2% of these cases were avoidable. The main causes of blindness were unoperated cataracts (59.2%) and glaucoma (21.1%). Uncorrected refraction error was the main cause of severe (19.7%) and moderate (58.6%) visual impairment. Cataract surgical coverage was 75.2%. 62.5% of the eyes operated for cataracts achieved a VA > 20/60 with available correction. The main barriers against cataract surgery were cost (27.7%) and the lack of availability or difficulty of geographical access to the treatment (24.6%). CONCLUSIONS: The prevalence of blindness and visual impairment in Honduras is similar to that of other Latin American countries. 67% of cases of blindness could be resolved by improving the response capacity of the ophthalmological services, especially of cataract surgery, improving optician services and incorporating eye care in primary health care.

Relation between frequency modulation direction selectivity and forward masking of inferior collicular neurons: a study on in vivo intracellular recording in mice / 生理学报

It has been reported that the frequency modulation (FM) or FM direction sensitivity and forward masking of central auditory neurons are related with the neural inhibition, but there are some arguments, because no direct evidence of inhibitory synaptic input was obtained in previous studies using extracellular recording. In the present study, we studied the relation between FM direction sensitivity and forward masking of the inferior collicular (IC) neurons using in vivo intracellular recordings in 20 Mus musculus Km mice. Thirty seven with complete data among 93 neurons were analyzed and discussed. There was an inhibitory area which consisted of inhibitory postsynaptic potentials (IPSP) at high frequency side of frequency tuning of up-sweep FM (FMU) sensitive neurons (n = 12) and at low frequency side of frequency tuning of down-sweep FM (FMD) selective neurons (n = 8), while there was no any inhibitory area at both sides of frequency tuning of non-FM sweep direction (FMN) sensitive neurons (n = 17). Therefore, these results show that the inhibitory area at low or high frequency side of frequency tuning is one of the mechanisms for forming FM sweep direction sensitivity of IC neurons. By comparison of forward masking produced by FMU and FMD sound stimuli in FMU, FMD and FMN neurons, the selective FM sounds could produce stronger forward masking than the non-selective in FMU and FMD neurons, while there was no forward masking difference between FMU and FMD stimuli in the FMN neurons. We suggest that the post-action potential IPSP is a potential mechanism for producing stronger forward masking in FMU and FMD neurons.

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...

Involvement of midbrain tectum neurokinin-mediated mechanisms in fear and anxiety

Electrical stimulation of midbrain tectum structures, particularly the dorsal periaqueductal gray (dPAG) and inferior colliculus (IC), produces defensive responses, such as freezing and escape behavior. Freezing also ensues after termination of dPAG stimulation (post-stimulation freezing). These defensive reaction responses are critically mediated by γ-aminobutyric acid and 5-hydroxytryptamine mechanisms in the midbrain tectum. Neurokinins (NKs) also play a role in the mediation of dPAG stimulation-evoked fear, but how NK receptors are involved in the global processing and expression of fear at the level of the midbrain tectum is yet unclear. The present study investigated the role of NK-1 receptors in unconditioned defensive behavior induced by electrical stimulation of the dPAG and IC of male Wistar rats. Spantide (100 pmol/0.2 μL), a selective NK-1 antagonist, injected into these midbrain structures had anti-aversive effects on defensive responses and distress ultrasonic vocalizations induced by stimulation of the dPAG but not of the IC. Moreover, intra-dPAG injections of spantide did not influence post-stimulation freezing or alter exploratory behavior in rats subjected to the elevated plus maze. These results suggest that NK-1 receptors are mainly involved in the mediation of defensive behavior organized in the dPAG. Dorsal periaqueductal gray-evoked post-stimulation freezing was not affected by intra-dPAG injections of spantide, suggesting that NK-1-mediated mechanisms are only involved in the output mechanisms of defensive behavior and not involved in the processing of ascending aversive information from the dPAG.

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.

Monitoring of anesthetic effect based on auditory response time / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the changes of auditory parameters during anesthesia and establish the assessment indicators for anesthesia monitoring in animal experiments.</p><p><b>METHODS</b>BALB/c mice of 4 to 6 weeks were given a single intraperitoneal dose of urethane, and the auditory evoked potential in the surgically exposed inferior colliculus in response to pure tone stimulation was recorded during urethane metabolism. The latency and amplitude data of the waves were extracted using Matlab software to analyze their variations during urethane metabolism.</p><p><b>RESULTS</b>The latency of the auditory evoked potential showed slight variation and was well correlated to time. The latency decreased progressively during urethane metabolism, fast in the initial 2 h and tending to stabilize afterwards.</p><p><b>CONCLUSION</b>The latency of the auditory evoked potential can be more suitable indicators than the amplitude for anesthetic effect monitoring.</p>

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@#(1) All 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. (2) The expression of GluR2 were different in different subnucleus of IC. (3) All sorts of neurons in IC expressed SYP in every postnatal groups, and the SYP expression in P6w groups was higher than others. (4) The expressions of GluR2 consistent 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.

Development of Human Neuro-digital Slides and Neuro-atlas for Neuroscience Tutorial I (Spinal Cord and Brain Stem) / 체질인류학회지

In order to present the optimal neuroscience tutorial material for medical students and researchers, this study is aimed to make neuro-digital slide and neuro-atlas based on the histological specimens of human spinal cord and brain stem. Cadavers which had agreed for organ donation for research purpose were used in this study. Brains and spinal cords were extracted within 24 hours after death, and then fixed with 10% neutral buffered formalin. Paraffin blocks were made with the following regions; 8 regions from the spinal cord (the levels of the upper cervical segment, the cervical enlargement, the upper thoracic segment, the mid thoracic segment, the lower thoracic segment, the upper lumbar segment, the lumbar enlargement, the sacral segment), 14 regions from the brain stem (the levels of the spinomedullary junction, the pyramidal decussation, the medial lemniscus decussation, the obex, the mid-olivary medulla, the upper medulla, the pontomedullary junction, the lower pons, the mid pons, the upper pons, the isthmus rhombencephali, the inferior colliculus, the superior colliculus, the posterior commissure). Using virtual microscope software, we made digital neuro-slides which can be used anywhere and anytime regardless of equipment of microscope. To help understanding anatomy and functions of nervous tissue, we also made neuro-atlas based on the digital slide images. As results, the outline and detailed structures of nuclei and tracts are easily discriminated and also matched with marks and nomenclatures of neuro-atlas. Moreover, the cytoarchitecture of each nucleus and histological features can be well distinguished. We hope that this product would be used as a useful neuroscience tutorial material for the medical and paramedical school students, clinical trainees like interns and residents, and also neuroscience researchers.