GABA-like immunoreactivity in the chick basilar papilla and the lagenar macula

Gamma-aminobutyric acid (GABA)-like immunoreactivity in the chick basilar papilla and lagenar macula was studied by using anti-serum against GABA coupled with glutaraldehyde to bovine serum albumin. GABA-like immunoreactivity was localized selectively in the cytoplasm of both tall and short hair cells in the basilar papilla, and in the hair cell cytoplasm of the lagenar macula. This immunocytochemical finding suggests that GABA may be an afferent neurotransmitter from the hair cell to the primary afferent neuron in the auditory organs of avians and is consistent with previous findings which suggest that GABA may act as an afferent neurotransmitter in the avian vestibular organs as well. However, the distribution pattern of GABA-like immunoreactivity in the afferent system is quite different from the distribution pattern previously described in the mammalian inner ear where GABA-like immunoreactivity is found exclusively within the efferent system.