English: An example of long-term potentiation recorded at Schaffer collateral/CA1 synapses in the hippocampus of rat brain. Graph: The rising slope of an extracellular EPSP field recorded in stratum radiatum of area CA1 in response to an extracellular stimulation of Schaffer collaterals. Test stimulus is a single shock of 100 us duration, approximately .01 mA. Tetanus is the test stimulus delivered at 100 Hz for 1s. Inset: a diagram of a hippocampal slice showing the electrode placement. Above the diagram are examples of the raw EPSP field potentials before and after tetanus.

Extended caption:

An example of long-term potentiation (LTP). The graph illustrates the analysis of a single field potential recording from a rat hippocampal slice. The inset shows the placement of the stimulating and recording electrode within the slice, and above, two raw traces of EPSP field potentials before and after tetanic stimulation. Field potentials were evoked by stimulation of Schaffer collaterals and recorded in stratum radiatum of the hippocampal slice (i.e. the Schaffer collateral/CA1 synapses). The individual points on the graph each represent the measurement of the rising slope of one EPSP field potential. Black squares indicate the measurements taken before tetanic stimulation. The green squares are measurements taken immediately after tetanic stimulation (PTP or post-tetanic potentiation) while the blue squares are measurements taken between 3 and 60 minutes after tetanization (LTP or long-term potentiation). Test stimuli were administered once every 30 sec. Tetanic stimulation was the test stimulus given at 100 Hz for 1 sec. Note how the amplitude of the EPSP field settles into a new, more elevated level after tetanic stimulation.