title: Rapid activation of dormant presynaptic terminals by phorbol esters.
abstract: Presynaptic stimulation stochastically recruits transmission according to the release probability (P(r)) of synapses. The majority of central synapses have relatively low P(r), which includes synapses that are completely quiescent presynaptically. The presence of presynaptically dormant versus active terminals presumably increases synaptic malleability when conditions demand synaptic strengthening or weakening, perhaps by triggering second messenger signals. However, whether modulator-mediated potentiation involves recruitment of transmission from dormant terminals remains unclear. Here, by combining electrophysiological and fluorescence imaging approaches, we uncovered rapid presynaptic awakening by select synaptic modulators. A phorbol ester phorbol 12,13-dibutyrate (PDBu) (a diacylglycerol analog), but not forskolin (an adenylyl cyclase activator) or elevated extracellular calcium, recruited neurotransmission from presynaptically dormant synapses. This effect was not dependent on protein kinase C activation. After PDBu-induced awakening, these previously dormant terminals had a synaptic P(r) spectrum similar to basally active synapses naive to PDBu treatment. Dormant terminals did not seem to have properties of nascent or immature synapses, judged by NR2B NMDAR (NMDA receptor) receptor subunit contribution after PDBu-stimulated awakening. Strikingly, synapses rendered inactive by prolonged depolarization, unlike basally dormant synapses, were not awakened by PDBu. These results suggest that the initial release competence of synapses can dictate the acute response to second messenger modulation, and the results suggest multiple pathways to presynaptic dormancy and awakening.
authors.affiliation: Department of Psychiatry, and Graduate Program in Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Chun Yun
authors.initials: CY
authors.lastname: Chang
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Jiang
authors.forename: Krista L
authors.initials: KL
authors.lastname: Moulder
authors.forename: Steven
authors.initials: S
authors.lastname: Mennerick
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006624:Hippocampus / Q000166:cytology; D007211:Indoles; D008301:Maleimides; D009474:Neurons / Q000166:cytology*; D018408:Patch-Clamp Techniques / Q000379:methods; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects*; D051381:Rats; D013395:Sucrose / Q000494:pharmacology; D013549:Sweetening Agents / Q000494:pharmacology; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: C465664:2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide; D002227:Carbazoles; D002273:Carcinogens; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D008301:Maleimides; D010880:Piperidines; D013549:Sweetening Agents; D050598:Vesicular Glutamate Transport Protein 1; D005576:Colforsin; D015240:Phorbol 12,13-Dibutyrate; D013395:Sucrose; D016291:Dizocilpine Maleate; C010739:ifenprodil; D002118:Calcium