Presynaptic depolarization rate controls transmission at an invertebrate synapse.
Second-order neurons L1-3 of the locust ocellar pathway make inhibitory synapses with each other. Although the synapses transmit graded potentials, transmission depresses rapidly and completely so that a synapse only transmits when the presynaptic terminal depolarizes rapidly. The rate at which a presynaptic neuron depolarizes determines the rate at which a postsynaptic neuron hyperpolarizes, and neurotransmitter is only released during a fixed 2 ms long period. Consequently, the amplitude of a postsynaptic potential depends on the rate rather than the amplitude of a presynaptic depolarization. Following a postsynaptic potential, a synapse recovers from depression over about a second. The synapse recovers from depression even if the presynaptic terminal is held depolarized.
Simmons
Peter J
PJ
School of Biology and School of Neurosciences and Psychiatry, University of Newcastle Upon Tyne, Framlington Place, Upon Tyne NE2 4HH, Newcastle, United Kingdom. p.j.simmons@ncl.ac.uk
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology*; D006110:Grasshoppers / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000502:physiology*; D017729:Presynaptic Terminals / Q000502:physiology* / Q000648:ultrastructure; D011930:Reaction Time / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*