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 mat ernal behaviour and olfactory recognition, the cellular mechanisms of actio n remain to be clarified. We examined the effects of OT on glutamatergic sp ontaneous excitatory postsynaptic currents (sEPSCs) in cultured granule cel ls with the use of whole-cell patch-clamp recordings. OT reversibly increas ed both the frequency and amplitude of sEPSCs. The effects of OT on sEPSCs were blocked by the selective OT receptor antagonists 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, s uggesting that OT acts presynaptically on step(s) in the release process do wnstream from calcium influx. OT augmented the membrane current in granule cells evoked by exogenous application of glutamate, indicating a postsynapt ic sire of action. These results indicate that OT facilitates sEPSCs in gra nule cells by both pre- and postsynaptic mechanisms. (C) 2001 Elsevier Scie nce Ireland Ltd. All rights reserved.