RESUMEN

The inbred mouse strain CBA/CaJ is a frequently used animal model of age-related hearing loss in humans. These mice display significant hearing loss at a relatively advanced age, similar to most humans, with progressive loss of hearing as the mouse continues to age. While important descriptions of hearing loss in this mouse strain at multiple ages have previously been published, shortcomings persist in the data for hearing over the lifespan of the mouse. Therefore, we analyzed auditory brainstem response threshold data from records maintained by our research group to yield an extensive database of thresholds over nearly the entire life span of the CBA/CaJ mouse (from 79 to 1085 days). Data was collected from in-house bred mice of CBA/CaJ stock, initially from The Jackson Laboratory. Data was collected using BiosigRZ software and TDT System III hardware. Thresholds were routinely measured in conjunction with behavioral and electrophysiological experiments; only responses from baseline or experimentally naïve animals were analyzed. The resulting data set comprised 376 female mice and 441 males. At the lowest and highest frequencies (8 & 32 kHz), initial thresholds were just under 30 dB SPL and increased slowly until they were significantly different at 16-18 months compared to 1-3 months age, with the difference increasing over subsequent ages. At the middle frequencies (12 & 16 kHz), initial thresholds were just under 20 dB SPL and increased until they became different from initial at 16-18 months. At 24 kHz, initial thresholds were just above 20 dB and became different from initial at 13-16 months of age. The rate of change of thresholds with age were similar for all frequencies until about 30 months of age, when 32 kHz threshold changes lagged behind other frequencies. Generally, CBA/CaJ mice in our colony display relatively low thresholds until approximately 16 months of age, depending on frequency. After 16-18 months, thresholds become significantly worse. After approximately 20-22 months thresholds increase linearly with age.

Asunto(s)

Longevidad , Presbiacusia , Humanos , Masculino , Ratones , Femenino , Animales , Preescolar , Envejecimiento/fisiología , Umbral Auditivo/fisiología , Ratones Endogámicos CBA , Ratones Endogámicos , Potenciales Evocados Auditivos del Tronco Encefálico

RESUMEN

Neurons in the anteroventral cochlear nucleus (AVCN) of DBA/2J (D2) and C57BL/6J (B6) mice were immunohistochemically labeled for the calcium binding protein parvalbumin (PV). Prior to this, mice were treated for 12h nightly with a "high-frequency" augmented acoustic environment (HAAE: repetitive bursts of a 70 dB sound pressure level, half-octave noise band centered at 20 kHz). This was done during the period that hearing loss occurs: pre-weaning to 55 days in D2 mice and weaning to 9 months in B6 mice. After HAAE treatment in D2 mice, high-frequency hearing loss was ameliorated and fewer PV-labeled neurons were found in the AVCN compared to untreated controls. HAAE treatment in B6 mice exacerbated high-frequency hearing loss, yet the number of PV-labeled AVCN neurons in treated mice did not differ significantly from that of control mice. The findings suggest that HAAE treatment provides relief from physiological stress caused by deprivation of auditory input from the impaired cochlea.

Asunto(s)

Estimulación Acústica , Núcleo Coclear/metabolismo , Parvalbúminas/metabolismo , Animales , Calcio/metabolismo , Femenino , Pérdida Auditiva de Alta Frecuencia/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Modelos Animales , Neuronas/metabolismo

RESUMEN

Mice of the C57BL/6J (B6) inbred strain exhibit genetic progressive sensorineural hearing loss and have been widely used as a model of adult-onset hearing loss and presbycusis. Males and females exhibit similar degrees of hearing loss until about 3 months of age, after which, the loss accelerates in females. This paper reviews research on how the B6 auditory system is affected by sex, gonadectomy (i.e., a reduction of gonadal hormone levels), and nightly exposure to moderately intense augmented acoustic environments (AAEs) - a low-frequency noise band (LAAE) or high-frequency band (HAAE). Several findings indicate a negative effect of ovarian hormones on the female B6 auditory system. Whereas the sex difference in high-frequency hearing loss was not significantly affected by gondadectomies, the female disadvantage in ABR thresholds at lower frequencies was erased by ovariectomy. Moreover, exposure to the LAAE or HAAE caused losses of hair cells that were more severe in intact females than in ovariectomized females or in males. Finally, intact females had more severe loss of neurons in the low-frequency region of the anterior ventral cochlear nucleus (AVCN) than other groups. In contrast, the presence of androgens had beneficial effects. Loss of hair cells and AVCN neurons after AAE exposure were more severe in orchidectomized males than in intact males. Ideas, hypotheses, and potential mechanisms concerning the findings are discussed.

Asunto(s)

Hormonas Esteroides Gonadales/fisiología , Pérdida Auditiva Sensorineural/etiología , Pérdida Auditiva Sensorineural/fisiopatología , Animales , Corteza Auditiva/fisiopatología , Umbral Auditivo , Cóclea/patología , Cóclea/fisiopatología , Núcleo Coclear/patología , Núcleo Coclear/fisiopatología , Modelos Animales de Enfermedad , Potenciales Evocados Auditivos del Tronco Encefálico , Femenino , Células Ciliadas Auditivas/patología , Pérdida Auditiva Sensorineural/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Modelos Neurológicos , Ruido/efectos adversos , Ovariectomía , Caracteres Sexuales , Ganglio Espiral de la Cóclea/patología

RESUMEN

Gonadectomized and intact adult C57BL/6J (B6) mice of both sexes were exposed for 12h nightly to an augmented acoustic environment (AAE): repetitive bursts of a 70dB SPL noise band. The high-frequency AAE (HAAE) was a half-octave band centered at 20kHz; the low-frequency AAE (LAAE) was a 2-8kHz band. The effects of sex, gonadectomy, and AAE treatment on genetic progressive hearing loss (a trait of B6 mice) were evaluated by obtaining auditory brainstem response (ABR) thresholds at ages 3-, 6-, and 9-months. At 9-months of age, hair cell counts (cytocochleograms) were obtained, and morphometric measures of the anteroventral cochlear nucleus (AVCN) were obtained. LAAE treatment caused elevation in ABR thresholds (8-24kHz), with the highest thresholds occurring in intact females. LAAE treatment caused some loss of outer hair cells in the basal half of the cochlea (in addition to losses normally occurring in B6 mice), with intact females losing more cells than intact males. The loss of AVCN neurons and shrinkage of tissue volume that typically occur in 9-month-old B6 mice was lessened by LAAE treatment in intact (but not gonadectomized) male mice, whereas the degenerative changes were exacerbated in intact (but not gonadectomized) females. These LAAE effects were prominent in, but not restricted to, the tonotopic low-frequency (ventral) AVCN. HAAE treatment resulted in some loss of neurons in the high-frequency (dorsal) AVCN. In general, LAAE treatment plus male gonadal hormones (intact males) had an ameliorative effect whereas HAAE or LAAE treatment plus ovarian hormones (intact females) had a negative effect on age-related changes in the B6 auditory system.

Asunto(s)

Estimulación Acústica/métodos , Vías Auditivas/patología , Umbral Auditivo , Cóclea/patología , Núcleo Coclear/patología , Potenciales Evocados Auditivos del Tronco Encefálico , Hormonas Esteroides Gonadales/metabolismo , Pérdida Auditiva/patología , Factores de Edad , Envejecimiento/patología , Animales , Vías Auditivas/metabolismo , Recuento de Células , Cóclea/metabolismo , Núcleo Coclear/metabolismo , Ambiente , Femenino , Células Ciliadas Auditivas Internas/patología , Células Ciliadas Auditivas Externas/patología , Pérdida Auditiva/genética , Pérdida Auditiva/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Neuronas/patología , Orquiectomía , Ovariectomía , Factores Sexuales

RESUMEN

The auditory system of rodents and other animals is affected by numerous genetic and environmental variables. These include genes that cause hearing loss, exposure to noise that induces hearing loss, ameliorative effects of an augmented acoustic environment on hearing loss, and effects of background noise on arousal. An understanding of genetic and environmental influences on hearing and auditory behavior is important for those who provide, use, and care for laboratory animals.

Asunto(s)

Animales de Laboratorio/fisiología , Percepción Auditiva/fisiología , Audición/fisiología , Ratones/fisiología , Ratas/fisiología , Animales , Núcleo Coclear/química , Complejo IV de Transporte de Electrones/análisis , Ambiente , Audición/genética , Pérdida Auditiva/genética , Pérdida Auditiva/veterinaria , Pérdida Auditiva Provocada por Ruido/veterinaria , Ruido , Enfermedades de los Roedores/genética

RESUMEN

Gonadectomized and surgically intact adult C57BL/6J (B6) mice of both sexes were exposed for 12h nightly to a high-frequency augmented acoustic environment (AAE): repetitive bursts of a half-octave noise band centered at 20 kHz, 70 dB SPL. The effects of sex, gonadectomy, and AAE treatment on genetic progressive hearing loss (exhibited by B6 mice) were evaluated by obtaining auditory brainstem response thresholds at ages 3-, 6-, and 9-months; hair cell counts (cytocochleograms) were obtained at 9 months. A sex difference in the rate of genetic progressive hearing loss in B6 mice (observed by earlier studies) was confirmed, with females exhibiting a faster rate of threshold elevations and more severe loss of hair cells at age 9 months. Gonadectomy had no consistent effects on the rate or severity of hearing loss in non-exposed mice of either sex. An unexpected finding was that the high-frequency AAE treatment caused additional ABR threshold elevations and hair cell loss. In an earlier study, the same high-frequency AAE treatment on DBA/2J mice ameliorated hearing loss. The most severe AAE-induced losses occurred in surgically intact females, suggesting a potentiating effect of ovarian hormone(s).

Asunto(s)

Umbral Auditivo , Cóclea/patología , Potenciales Evocados Auditivos del Tronco Encefálico , Ruido/efectos adversos , Orquiectomía , Ovariectomía , Estimulación Acústica , Análisis de Varianza , Animales , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Caracteres Sexuales

RESUMEN

DBA/2J (D2) mice, which exhibit very early progressive sensorineural hearing loss, were treated for 12h nightly with an augmented acoustic environment (AAE) initiated before the onset of hearing. The AAE consisted of repetitive bursts of a 70 dB sound pressure level, half-octave noise band centered at 20 kHz (i.e. low frequencies were excluded). At 55 days of age, AAE-treated mice, compared to control mice, exhibited less elevation of auditory brainstem response thresholds for tone frequencies from 16 to 32 kHz and fewer missing outer hair cells in the high-frequency tonotopic region of the cochlea. The dorsal region of their anteroventral cochlear nucleus (most strongly stimulated by the AAE) was larger, had more surviving neurons, and larger neurons than those of untreated control mice. These and previous findings using an AAE band containing lower frequencies indicate that AAE treatment effects are frequency-related. The findings provide support for the hypothesis that the beneficial effects of AAE treatment on the cochlea are associated with increased physiological activity evoked by the AAE, and the central AAE effects result from increased AAE-evoked neural activity and a healthier cochlea providing the auditory input.

Asunto(s)

Cóclea/fisiopatología , Núcleo Coclear/fisiopatología , Ambiente , Pérdida Auditiva Provocada por Ruido/fisiopatología , Pérdida Auditiva Sensorineural/genética , Ruido/efectos adversos , Análisis de Varianza , Animales , Umbral Auditivo/fisiología , Cóclea/lesiones , Núcleo Coclear/lesiones , Potenciales Evocados Auditivos del Tronco Encefálico , Femenino , Masculino , Ratones , Ratones Endogámicos DBA , Distribución Aleatoria

RESUMEN

The three general approaches for assessing the mouse auditory system presented in UNITS 8.21B-8.21D are complementary, but differ in the time required for testing as well as the goals of the tests: the auditory brainstem response (ABR; UNIT 8.21B), distortion product otoacoustic emissions (DPOAE; UNIT 8.21C), and lick suppression behavioral test (UNIT 8.21D). Various issues that need to be addressed in the testing of mouse hearing are discussed in this overview, including accurate nomenclature of the strain and/or mutations, environmental versus genetic influences, selection of frequencies to be tested, and appropriate animal care and use.

Asunto(s)

Vías Auditivas/fisiología , Conducta Animal/fisiología , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Emisiones Otoacústicas Espontáneas/fisiología , Estimulación Acústica/métodos , Animales , Ratones

RESUMEN

The ABR is an electroencephalographic response measured with scalp electrodes. It provides a quick, easy, and reliable method for physiological assessment of auditory sensitivity in mice. A series of brief tone pips or clicks is presented to an anesthetized mouse at a high rate of speed; each click evokes waves of neural activity in the brainstem that are computer-averaged so they are differentiated from non-auditory background voltages. The intensity of the clicks is reduced in steps until an ABR can no longer be discerned, thereby defining the ABR threshold, which is closely related to the hearing threshold. Key procedural issues are: (1) accurate calibration of the acoustics (what sounds arrive at the mouse's ear), (2) anesthetization of the mouse, (3) setting up the recording electrodes, (4) the protocol for presenting acoustic stimuli and obtaining thresholds, and (5) interpretation of ABR data.

Asunto(s)

Estimulación Acústica/métodos , Umbral Auditivo/fisiología , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Estimulación Acústica/instrumentación , Animales , Audiometría/instrumentación , Audiometría/métodos , Percepción Auditiva/fisiología , Ratones , Proyectos de Investigación/normas

RESUMEN

DBA/2J (D2) mice, which exhibit very early progressive sensorineural hearing loss, were treated nightly with an augmented acoustic environment (AAE) initiated before the onset of hearing, and consisting of repetitive bursts of a 70-dB sound pressure level (SPL), 4-25 kHz noise band. At 55 days of age, AAE-treated mice exhibited less elevation of auditory brainstem response thresholds, fewer missing hair cells, and greatly reduced loss of anteroventral cochlear nucleus (AVCN) volume and neuron number compared to untreated control mice. It was hypothesized that the central neuroprotective effect was associated with increased afferent input to AVCN neurons evoked by the AAE as well as a healthier cochlea.

Asunto(s)

Estimulación Acústica , Cóclea/fisiología , Núcleo Coclear/fisiología , Pérdida Auditiva Sensorineural/prevención & control , Pérdida Auditiva Sensorineural/terapia , Animales , Recuento de Células , Cóclea/patología , Núcleo Coclear/patología , Ambiente , Potenciales Evocados Auditivos del Tronco Encefálico , Femenino , Células Ciliadas Auditivas/patología , Pérdida Auditiva Sensorineural/patología , Masculino , Ratones , Ratones Endogámicos DBA , Neuronas/patología , Caracteres Sexuales

RESUMEN

Aging C57BL/6J (C57) mice (1-30 months old), were used to study calcium-binding protein immunoreactivity (parvalbumin, calbindin and calretinin) in the cochlear nucleus. A quantitative stereological method, the optical fractionator was used to determine the total number of neurons, and the total number of immunostained neurons in the posteroventral- and dorsal cochlear nuclei (PVCN and DCN). A statistically significant age-related decrease of the total number of neurons was found in the PVCN and DCN using Nissl staining. In the DCN, an age-related increase in the total number of parvalbumin-positive neurons was found, while no changes in the total number of calbindin or calretinin positive neurons were demonstrated. In the PVCN, the total number of parvalbumin, calbindin, or calretinin positive neurons remained stable with increasing age. The percentage of parvalbumin, calbindin, and calretinin positive neurons significantly increased in the DCN, and the percentage of parvalbumin and calbindin-positive neurons increased in the PVCN. These findings imply that there is a relative up-regulation of calcium-binding proteins in neurons that had not previously expressed these proteins. This plastic response in the profoundly hearing impaired C57 mouse may be a survival strategy for cochlear nucleus neurons.

Asunto(s)

Envejecimiento/metabolismo , Proteínas de Unión al Calcio/metabolismo , Núcleo Coclear/metabolismo , Pérdida Auditiva Central/metabolismo , Regulación hacia Arriba/fisiología , Adaptación Fisiológica/fisiología , Factores de Edad , Animales , Calbindina 2 , Calbindinas , Recuento de Células , Supervivencia Celular/fisiología , Núcleo Coclear/citología , Núcleo Coclear/fisiopatología , Femenino , Pérdida Auditiva Central/genética , Pérdida Auditiva Central/fisiopatología , Trastornos Heredodegenerativos del Sistema Nervioso/genética , Trastornos Heredodegenerativos del Sistema Nervioso/metabolismo , Trastornos Heredodegenerativos del Sistema Nervioso/fisiopatología , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Plasticidad Neuronal/fisiología , Neuronas/citología , Neuronas/metabolismo , Parvalbúminas/metabolismo , Proteína G de Unión al Calcio S100/metabolismo , Especificidad de la Especie

RESUMEN

Genetic progressive sensorineural hearing loss in mice of the C57BL/6J (B6) inbred strain begins at high frequencies during young adulthood and is severe by 12 months (middle age). Nightly treatment with an augmented acoustic environment (AAE)--12-hour periods of exposure to repetitive noise bursts of moderate intensity, begun at age 25 days--resulted in less severe hearing loss compared with control mice. Cochlear histopathological correlates of AAE treatment, assessed at 12-14 months of age, included lessened severity of progressive loss of outer hair cells in both sexes as well as small savings of spiral ganglion cells in females and inner hair cells in males. AAE effects on the number of surviving neurons (age 12-14 months) in the anterior ventral cochlear nucleus (AVCN) depended on sex. Compared with controls, the loss of AVCN neurons that typically accompanies the initial period of hearing loss (between 2 and 7 months of age) was not significantly affected by AAE treatment in females. In contrast, males treated with the AAE exhibited more severe loss of neurons in the dorsal and ventral extremes of the AVCN than male controls of the same age. AAE treatment begun at age 3-5 months resulted in significant but less severe loss of AVCN neurons in 1-year-old male mice.

Asunto(s)

Estimulación Acústica , Umbral Auditivo/fisiología , Núcleo Coclear/patología , Células Ciliadas Auditivas/efectos de la radiación , Caracteres Sexuales , Envejecimiento/fisiología , Análisis de Varianza , Animales , Recuento de Células , Supervivencia Celular/efectos de la radiación , Modelos Animales de Enfermedad , Relación Dosis-Respuesta en la Radiación , Femenino , Pérdida Auditiva Sensorineural/fisiopatología , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Inhibición Neural/efectos de la radiación , Especificidad de la Especie , Ganglio Espiral de la Cóclea/citología , Ganglio Espiral de la Cóclea/efectos de la radiación , Factores de Tiempo

RESUMEN

A high-throughput phenotype screening protocol was used to measure the acoustic startle response (ASR) and prepulse inhibition (PPI) in mice. ASRs were evoked by noise bursts; prepulses for PPI were 70 dB sound pressure level tones of 4, 12, and 20 kHz. Forty inbred strains of mice were tested (in most cases using 10 males and 10 females of each strain). The data on both the ASR and PPI had high internal and test-retest reliability and showed large differences among inbred strains, indicative of strong genetic influences. Previously obtained measures of hearing sensitivity in the same inbred strains were not significantly correlated with ASR or PPI measures.

Asunto(s)

Reflejo de Sobresalto/genética , Estimulación Acústica , Animales , Femenino , Masculino , Ratones , Ratones Endogámicos , Fenotipo , Valores de Referencia