Study on olfactory function in GABAC receptor/channel ρ1 subunit knockout mice

The GABAC receptor/channel ρ1 subunit plays an important role in the inhibitory pathway and sensory processing in the retina and spinal cord. Although it was suggested that the ρ1 subunit plays a role in olfactory sensations, the precise role of the ρ1 subunit in olfactory sensory function is still not clear. In the present study, we report that olfactory function was significantly altered in ρ1 subunit knockout (rho1−/−) mice compared to its wildtype counterpart. The ρ1 subunit mRNA, detected by reverse transcription (RT)-PCR experiments, was expressed in the olfactory bulb of wild-type mice. Expression of ρ1 subunit proteins in the olfactory bulb was detected by immunohistochemistry in mitral cells in the mitral cell layer. Neither mRNA nor proteins of the ρ1 subunit were found in olfactory bulb neurons in rho1−/− mice. Alterations of olfactory function in rho1−/− mutant mice compared to their wildtype littermates were examined by olfactory behavioral test. We found that sensitivity to the smell of citral odorant in rho1−/− mice was significantly greater compared to that of wildtype mice. Our results indicate that the GABAC ρ1 subunit acts in olfactory bulb neurons as an inhibitory modulator that affects the process of olfactory signaling transmission.