Abnormal synaptic transmission in the olfactory bulb of Fyn-kinase-deficient mice

We studied synaptic transmission in the granule cells in the olfactory bulb of the homozygous Fyn (a nonreceptor type tyrosine kinase)-deficient (fynz/fynz) and heterozygous Fyn-deficient (+/fynz) mice by using slice preparations from the olfactory bulb. Stimulation to the lateral olfactory tract and/or centrifugal fibers to the olfactory bulb evoked field excitatory postsynaptic potentials (fEPSPs) in the granule cells. In +/fynz mice, fEPSPs were augmented by bicuculline, a gamma-aminobutyric acid (GABAA) antagonist and picrotoxin, whereas fEPSPs in fynz/fynz mice were much less sensitive to bicuculline and picrotoxin. Application of D-2-amino-5-phosphonopentanoic acid had no effect but 6-cyano-7-nitroquinoxaline-2,3-dione produced almost complete block of fEPSPs in both +/fynz mice and fynz/fynz mice. (1S,3R)-1-aminocyclo-pentane-1.3-dicarboxylate, an agonist of metabotropic glutamate receptors caused a similar depression of fEPSPs in both +/fynz and fynz/fynz mice. In +/fynz mice tetanic stimulation to the lateral olfactory tract and/or centrifugal fibers induced N-methyl-D-aspartate (NMDA)-dependent long-term potentiation (LTP) of fEPSPs, whereas LTP was impaired in fynz/fynz mice. Our results demonstrate altered functions of GABAA and NMDA receptors in the olfactory system of Fyn-deficient mice.