Post-Grant Reports


Using In Situ Hybridization to Locate GABA Receptors in Zebrafish: Part II

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Molecular and Cellular Neuroscience | Neuroscience and Neurobiology | Sense Organs


Decades of research have provided ample evidence that the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) plays a role in inner ear circuitry. GABA binds to two types of receptors (GABARs): ionotropic GABAARs and G protein coupled GABABRs. Many GABAR subunits have been localized to both cochlear and vestibular labyrinth tissues, and in many species, hair cells of the vestibular labyrinth, but not the cochlea, synthesize GABA themselves. The role of this local source of GABA within the periphery is incompletely understood. We seek to use the zebrafish lateral line to model and further understand peripheral vestibular GABA signaling.

We have used immunohistochemistry, RT-PCR, and in situ hybridization to identify and locate key players in GABA circuitry, namely GABA, glutamate decarboxylase (GAD), and GABAR subunits. We have localized both GABA and GAD to lateral line hair cells. This suggests that, like some vestibular hair cells, lateral line hair cells synthesize GABA and are therefore a good model with which to further understand the role of this neurotransmitter in the vestibular periphery. Using RT-PCR, we amplified 25 out of 26 GABA-related transcripts from larval tissue, and we have identified 13 as candidate lateral line genes. We have begun to locate candidate genes using in situ hybridization, and thus far have found that gabbr1a, which codes for GABABR subunit B1a, is expressed by cells of the posterior and anterior lateral line ganglia, suggesting possible postsynaptic afferent GABABR expression, and modulation of afferent activity by hair cell GABA release. Finally, we have begun to assay the effects of GABAR modulators on the lateral-line dependent rheotaxis behavior. We have found that GABAR antagonists increase the sensitivity of larvae to modest but not strong water currents. Together our results suggest that GABA may be released from lateral line hair cells and may function to modulate behavioral responses to sensory stimuli.


This research was conducted as part of a Linfield College Student-Faculty Collaborative Research Grant in 2017, funded by the Office of Academic Affairs.

Student collaborators were Jackson O'Keefe, Austin Ramsay, and Shannon Apgar.

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