regulates regulates has start location has end location process has causal agent peptide zwitterion chemical synaptic transmission presynapse postsynapse retrograde trans-synaptic signaling by neuropeptide retrograde trans-synaptic signaling by neuropeptide, modulating synaptic transmission GO:0099083 Note that this term was created for the SynGO project, and will be obsoleted when the SynGO annotations are made in Noctua. biological_process Modulation of synaptic transmission by cell-cell signaling across the synaptic cleft from postsynapse to presynapse, mediated by a neuropeptide. trans-synaptic signaling trans-synaptic signaling by neuropeptide, modulating synaptic transmission