IAC-USNC Methods in Neuroscience- goldfish mauthner cell recording page2

Recording the Mauthner cell's extracellular field potential Click HERE for 20 second video (3MB)
The Mauthner cell dendrite can be located electrophysiologically by searching for the cell's extremely large and characteristic antidromic field potential (yellow arrow - generated via spinal cord stimulation). A series of electrode penetrations is generally begun 400um from the midline and 2/3 of the way between the facial lobe and the IV ventricle.	As the electrode approaches the Mauthner cell axon hillock or soma, the field increases...	and increases. The field can be as large as 40mV near the axon hillock, where the largest field is generated. Here the calibration pulse before the stimulus artifact (orange arrow) is 2mV in amplitude and 1ms long.
Here the cell was accidently penetrated and an action potential was recorded (the action potential is off the oscilloscope screen).	It was clear that this signal (now on the screen) was an action potential because it gave an "all or none" response to a threshold stimulus. The calibration pulse is now 10mV. The action potential in the soma is only ~40mv, because it is generated at the axon hillock.	Here the threshold stimulus failed to produce an action potential.

Recording Shunting Inhibition Click HERE for 1 min video (10MB)
Two action potentials evoked by two stimuli to the VIII nerve. The second AP is reduced in amplitude because of shunting inhibition.	Changing the time between the two stimuli produces action potentials of different amplitudes...	and reveals a minimum in the AP amplitude at the point where inhibition is maximal.
AP amplitude increases as the time between the simuli increases and the inhibition dies.	Note the small depolarizing IPSP in the baseline. Its waveform mirrors the change in AP amplitude caused by the shunting inhibition.	As the stimuli are delivered further apart in time, the amplitude of the second AP recovers. Full recovery is not shown on this screen.