Short Term Plasticity At The Orn Essay

1054 Words May 23rd, 2016 null Page
Short-term plasticity at the ORN  PN synapse could result in PN responses that are strongest during the rising phase of the ORN response since the ORN  PN synapses display short-term depression that causes ORN spikes that arrive later to produce smaller postsynaptic potentials than the ones produced by earlier spikes. In depressing synapses, successive action potentials result in smaller and smaller postsynaptic responses. The reduction in postsynaptic responses could be due to smaller amount of neurotransmitter release by the presynaptic neuron. Depressing synapses are characterized by high starting release probability. Thus, there are large amounts of neurotransmitter release at beginning of stimulus train. However, this large amount of release depletes the number of vesicles readily available for release. As a result, the amount of release declines as stimulus train proceeds. Thus, during the course of ORN activation, the depressing ORN  PN synapse causes the PN response to decline over the course of ORN activation. This explains why the PN responses decay early, while the ORN responses continue to build slowly. Lateral inhibition from inhibitory LNs could result in PN responses that are strongest during the rising phase of the ORN response since the LNs synapse onto ORN axon terminals and, as a result, reduce the efficiency of transforming ORN action potentials to neurotransmitter release. LN activation provides a negative feedback control of the synaptic output of…

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