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Auditory brainstem response (ABR) in spontaneously epileptic rats (SER) and their parent mutants
Insights
Spontaneously epileptic rats (SER) and their parent mutants exhibit hearing impairments due to auditory brainstem response (ABR) abnormalities. Histopathology reveals vacuolation in the brainstem, suggesting a central auditory pathway dysfunction.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Genetics
Background:
- Spontaneously epileptic rats (SER) are a double mutant model exhibiting epilepsy.
- Understanding the auditory development in these models is crucial for neurological research.
Purpose of the Study:
- To investigate the postnatal development of the auditory brainstem response (ABR) in SER and their parent mutants.
- To identify the underlying causes of hearing impairment in these rat models.
Main Methods:
- Repeated ABR recordings were performed on SER, tremor rats, zitter rats, and control rats from 2 to 13 weeks of age.
- Electrocochleography was used to assess compound action potential latency.
- Histopathological examination of cochlear nuclei, brainstem, and cochlea was conducted.
Main Results:
- Tremor rats and controls showed normal ABR development, while tremor rats exhibited prolonged latency and reduced amplitude.
- Zitter rats, SER, and SER-N displayed only Wave I with prolonged latency and reduced amplitude.
- Histopathology revealed vacuolation in the cochlear nuclei and brainstem of tremor rats and SER.
Conclusions:
- SER and their parent mutants exhibit significant auditory pathway dysfunction.
- Deafness in these models likely results from impairments in the inner ear, cochlear nerve, and brainstem.
- Vacuolation in the brainstem suggests a central component to the auditory deficit.
Abstract:
Postnatal development of auditory brainstem response (ABR) in spontaneously epileptic rats (SER; zi/zi, tm/tm), a double mutant, their parent mutants, tremor rats (tm/tm) and zitter rats (zi/zi), and Kyo:Wistar rats (control), was studied by repeated ABR recordings from 2 to 13 weeks of age. In tremor rats and Kyo:Wistar rats at 2 weeks of age, ABR pattern was almost the same and 2 or 3 waves were identified. However, no further development in ABR was observed in tremor rats and prolongation of latency and lowering of amplitude were marked. Only wave I with prolonged latency and lowered amplitude was recognized in zitter rats, SER and SER-N (zitter phenotype without epilepsy; zi/zi, tm/+ or zi/zi, +/+). ABR pattern was almost the same from 2 to 13 weeks of age in them. Electrocochleography revealed delay of N1 latency of compound action potential in SER. Vacuolation was observed in the cochlear nuclei and the brainstem of tremor rats and SER from 3 weeks of age in histopathological examination. The organ of Corti and cochlear nerve of tremor rats and SER exhibited no remarkable histopathological findings. The deafness in SER and its parent mutants was considered to occur as a result of impairment of inner ear, cochlear nerve and brainstem as well.