Synaptic transmission at single glomeruli in the turtle cerebellum.
We have recorded from the granular layer of the turtle cerebellum extracellular unitary potentials that appear to reflect pre- and postsynaptic events at the synapse between a single swelling of a mossy fiber and the dendritic tips of several granule cells. The presynaptic component is an all-or-none potential. It can be directly activated by spinal stimulation and is unaltered by repetitive activity or by high concentrations of magnesium. The postsynaptic component is a graded potential. It follows the presynaptic component by approximately 1 millisecond and is depressed by repetitive activity and by high concentrations of magnesium. The recording of large potentials produced by the flow of postsynaptic current within a single glomerulus suggests powerful transmission. Electron micrographs demonstrate large cerebellar glomeruli in the turtle and a substantial accumulation of mitochondria in the dendritic tips of granule cells.
D000200:Action Potentials; D000818:Animals; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D004558:Electric Stimulation; D008854:Microscopy, Electron; D008928:Mitochondria; D013116:Spinal Cord / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles; D014426:Turtles