The expression of glutamate receptor gene family in the vestibular Scarpa's ganglion (VG) of rat was determined using molecular biological techniques including reverse transcription (RT), polymerase chain reaction (PCR), amplification, DNA sequencing, and immunocytochemistry. Oligonucleotide primers were designed from the previously cloned sequences of the AMPA-selective glutamate receptors (GluR1-4), KA-selective glutamate receptors (GluR5-7, KA1&2), NMDA-selective glutamate receptors (NMDAR1&2), and metabotropic glutamate receptors (mGluR1-4). The cDNAs synthesized from the VG mRNAs were amplified with the specific primers for the subunits of each glutamate receptor gene family. Analysis of the nucleotide sequences of the amplified cDNAs identified the expression of GluR1-4, GluR5, and NMDAR1 in the VG. Sequence analysis identified the expression of all the four subunits of GluR1-4 in two alternative spliced versions named "flip" and "flop" in the VG. In an immunocytochemical study, a large number of VG neurons showed only GluR2/3-like immunoreactivity (IR) while GluR1- or GluR4-IR could not be determined in the VG. The present study suggested that the subunits of GluR1-4, GluR5, and NMDAR1 may be assembled into the hetero-oligomeric glutamate receptor complex in the VG and that the VG neuron-specific stoichiometry of the receptor complex may be functionally significant for the afferent signal transduction in the rat peripheral vestibular system.