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.
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
Peter J
PJ
Simmons
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*