Analysis of 5-HT-induced short-term facilitation at Aplysia sensorimotor synapse during bursts: increased synaptic gain that does not require ERK activation.
The 5-HT-induced synaptic plasticity of Aplysia sensorimotor synapses has typically been probed by firing a single presynaptic spike. In this study, 5-HT-induced synaptic plasticity was probed with brief bursts of spikes (10 Hz, 1 s), which are more behaviorally relevant stimuli. Because such bursts provide a greater challenge to the release machinery than single spikes, their use may reveal additional aspects of synaptic modulation, and, in particular, the role of extracellular signal-regulated protein kinase (ERK), which has recently been implicated in several examples of short- and long-term synaptic plasticity. Excitatory postsynaptic currents (EPSCs) were characterized by their amplitudes. In addition, two kinetic measurements, time to peak and decay time constant, were determined for the initial and last EPSCs of each burst. Application of 5-HT produced a uniform increase in gain by facilitating each EPSC elicited during a burst of spikes without affecting the kinetics of the initial or last EPSC. These data suggest that short-term facilitation during a burst is mediated largely by processes such as those that affect the size of the releasable pool or rate of vesicle mobilization rather than by an increase in the duration of the presynaptic action potential. An ERK cascade inhibitor (U0126) had no effect on the 5-HT-mediated facilitation of either the initial EPSC or EPSCs elicited late in the burst.
Phares
Gregg A
GA
Department of Neurobiology and Anatomy, W.M. Keck Center for Learning and Memory, The University of Texas Medical School at Houston, 6431 Fannin St., MSB 7.046, Houston, Texas 77030, USA.
Byrne
John H
JH
D000818:Animals; D001048:Aplysia; D002070:Butadienes / Q000494:pharmacology; D004347:Drug Interactions; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D017952:Ganglia, Invertebrate / Q000166:cytology; D066298:In Vitro Techniques; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D009473:Neuronal Plasticity / Q000187:drug effects* / Q000528:radiation effects; D009570:Nitriles / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D012701:Serotonin / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects* / Q000528:radiation effects; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D013997:Time Factors
D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; D012701:Serotonin; D048049:Extracellular Signal-Regulated MAP Kinases