A transient, neuron-wide form of CREB-mediated long-term facilitation can be stabilized at specific synapses by local protein synthesis

In a culture system where a bifurcated Aplysia sensory neuron makes synapse s with two motor neurons, repeated application of serotonin (5-HT) to one s ynapse produces a CREB-mediated, synapse-specific, longterm facilitation, w hich can be captured at the opposite synapse by a single pulse of 5-HT. Rep eated pulses of 5-HT applied to the cell body of the sensory neuron produce a CREB-dependent, cell-wide facilitation, which, unlike synapse-specific f acilitation, is not associated with growth and does not persist beyond 48 h r. Persistent facilitation and synapse-specific growth can be induced by a single pulse of 5-HT applied to a peripheral synapse. Thus, the short-term process initiated by a single pulse of 5-HT serves not only to produce tran sient facilitation, but also to mark and stabilize any synapse of the neuro n for long-term facilitation by means of a covalent mark and rapamycin-sens itive local protein synthesis.