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Updated: Aug 30, 2026
Auditory Brainstem Response and Outer Hair Cell Whole-cell Patch Clamp Recording in Postnatal Rats
Published on: May 24, 2018
The opioid receptors in inner ear of different stages of postnatal rats
Pansiri Phansuwan-Pujito1, Ladda Saleema, Sujira Mukda
1Department of Anatomy, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand.
Insights
The opioid system plays a role in hearing. Opioid receptor expression in the rat inner ear changes during development, suggesting involvement in hearing onset and function.
Area of Science:
- Neuroscience
- Otolaryngology
- Developmental Biology
Background:
- Emerging evidence suggests the opioid system influences auditory function.
- Understanding opioid receptor roles in the inner ear is crucial for auditory development research.
Purpose of the Study:
- To investigate the developmental expression and distribution of opioid receptor mRNAs and proteins in the rat inner ear.
- To correlate opioid receptor expression patterns with the onset of hearing.
Main Methods:
- Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to analyze mRNA levels of delta (DOR), kappa (KOR), and mu (MOR) opioid receptors.
- Immunocytochemical labeling to determine the spatial and temporal distribution of opioid receptor proteins in inner ear tissues.
Main Results:
- Opioid receptor mRNAs (DOR, KOR, MOR) exhibited distinct developmental expression patterns in the cochlea.
- Immunoreactivity for DOR, KOR, and MOR proteins showed unique distributions in the organ of Corti, spiral ganglion, and limbus during development.
- Receptor expression patterns varied across cell types (hair cells, supporting cells, neurons) and changed from birth to postnatal day 16.
Conclusions:
- Each opioid receptor subtype displays specific temporal and spatial developmental patterns within the inner ear.
- These developmental patterns suggest a role for the opioid system in the maturation and function of the auditory system.
- The findings provide further evidence for the opioid system's involvement in inner ear development and hearing.
Abstract:
There is increasing evidence that the opioid system has a role in hearing. To provide further evidence for such a role, the expression of opioid receptor mRNAs and proteins in the inner ear of rats was studied during development from birth (P0) to postnatal day 16 (P16). A semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was employed to detect changes in the expression of delta- (DOR) kappa- (KOR) and mu- (MOR) opioid receptor mRNAs in rat cochleae at P0, P4, P8 and P16. Expression of DOR mRNA levels steadily increased from P0 to P8 with no further increases by P16. KOR mRNA was expressed at a relatively high level at P0 and P4 followed by a decrease while MOR mRNA was expressed at a low level at P0 and P4 followed by an increase by P8 and P16. Immunocytochemical labelling of inner ear sections revealed unique developmental and distribution patterns of opioid receptors. In the organ of Corti DOR immunoreactivity (DOR-IR) was detected in hair cells from P4. In contrast MOR-IR was present only in supporting cells at P0-P16. In the spiral ganglion all three receptor subtypes were expressed from P0 on nerve cell soma and qualitatively appeared to increase with age. Also DOR-IR and MOR-IR were detected at P8 and P16 in nerve fibers within the spiral ganglion. In the limbus DOR-IR was detected at P8 and P16 on cells proximal to the tectorial membrane while MOR-IR was detected more distally. In general these findings demonstrate that within the inner ear each receptor subtype follows specific temporal and spatial developmental patterns, some of which may be associated to the onset of hearing. The data provide further evidence that the opioid system may play a role in the development and functioning of the inner ear.
