NITRIC-OXIDE ACTS AS A RETROGRADE MESSENGER DURING LONG-TERM POTENTIATION IN CULTURED HIPPOCAMPAL-NEURONS

We examined long-term potentiation (LTP) at synapses between hippocamp al neurons in dissociated cell culture following presynaptic, postsyna ptic, or extracellular application of a nitric oxide (NO) scavenger, a n inhibitor of NO synthase, and a membrane-impermeant NO donor that re leases NO only upon photolysis with UV light. Our results indicate tha t NO is produced in the postsynaptic neuron, travels through the extra cellular space, and acts directly in the presynaptic neuron to produce long-term potentiation, supporting the hypothesis that NO acts a retr ograde messenger during LTP.