Oxytocin enhances presynaptic and postsynaptic glutamatergic transmission between rat olfactory bulb neurones in culture.

Although oxytocin (OT) within the olfactory bulb has been implicated in maternal behaviour and olfactory recognition, the cellular mechanisms of action remain to be clarified. We examined the effects of OT on glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) in cultured granule cells with the use of whole-cell patch-clamp recordings. OT reversibly increased both the frequency and amplitude of sEPSCs. The effects of OT on sEPSCs were blocked by the selective OT receptor antagonist desGly-NH(2)(9),d (CH(2))(5)-[Thy(Me)(2),Thr(4)]-ornithine vasotocin. OT had no detectable effect, however, on high voltage-activated Ca2+ currents in mitral/tufted cells, suggesting that OT acts presynaptically on step(s) in the release process downstream from calcium influx. OT augmented the membrane current in granule cells evoked by exogenous application of glutamate, indicating a postsynaptic site of action. These results indicate that OT facilitates sEPSCs in granule cells by both pre- and postsynaptic mechanisms.