Distribution of GABA-like immunoreactivity in guinea pig vestibular cristae ampullaris.

Post-embedding immunocytochemical techniques were used to assess distribution of gamma-aminobutyric acid (GABA) in the guinea pig cristae ampullaris. GABA-like immunoreactivity (GABA-LIR) was found in the cytoplasm of both type I (HCI) and type II hair cells (HCII), in the afferent calyx (AC) contacting HCI and some myelinated fibers in the subjacent stroma. HCI and its calyceal contacts showed variation in GABA-LIR, suggesting different populations in HCI and AC. These results support a putative afferent neurotransmitter role of GABA in HC and a possible degradation site of GABA in AC.