OLFACTORY RECIPROCAL SYNAPSES - DENDRITIC SIGNALING IN THE CNS

Synaptic transmission between dendrites in the olfactory bulb is thoug ht to play a major role in the processing of olfactory information. Gl utamate released from mitral cell dendrites excites the dendrites of g ranule cells, which in turn mediate GABAergic dendrodendritic inhibiti on back onto mitral dendrites. We examined the mechanisms governing re ciprocal dendritic transmission in rat olfactory bulb slices. We find that NMDA receptors play a critical role in this dendrodendritic inhib ition. As with axenic synapses, the dendritic release of fast neurotra nsmitters relies on N- and P/Q-type calcium channels. The magnitude of dendrodendritic transmission is directly proportional to dendritic ca lcium influx. Furthermore, recordings from pairs of mitral cells show that dendrodendritic synapses can mediate lateral inhibition independe ntly of axonal action potentials.