Look under the microscope to identify the nature of the clog.
How to prevent clogs:
How to unclog your chip:
Please refer to the ScreenChip selection guide
As long as the worm’s pharynx is located between the electrodes of the chip, you will be able to detect a clear signal. Please note that the recording channel is tapered to allow worms of varying sizes to fit. This means that as the worm slides within the recording channel, the seal (contact of the cuticle to the walls of the channel) will change, thereby changing the amplitude of the signal detected. The other parameters recorded will not be affected.
Day 1 N2 adults do not readily pump in the absence of a pumping stimulant. In saline buffer such as M9 or S-Basal, these worms typically pump between 0 Hz and 3 Hz. The variability of pump frequency within one population can be high and on average, the pump frequency of a N2 Day 1 worm population is below 1 Hz.
We recommend that you use pumping stimulants in the chip, such as serotonin or bacteria, in order to trigger pharyngeal pumping. Using a pumping stimulant will allow you observe a higher number of pumps, making the statistical analysis more stringent. In addition, since the pumps are sparse during a single recording, the variability of interpump intervals is usually high.
We use Serotonin hydrochloride for our in-house experiments and recommend that you use it as well. 10mM of serotonin in M9 will allow you to stimulate pharyngeal pumping to its maximum frequency (4.5 to 5.5 Hz in healthy young adult N2 worms). For your convenience, we offer pre-weighed aliquots of serotonin. See RediPrep™ Serotonin.
When feeding worms within the ScreenChip we recommend using freeze-dried bacteria. Freeze-dried bacteria ensures a consistent food source based on bacteria quality, number of cells/mL. See Instant freeze-dried OP50.
The ScreenChip is make in part of PDMS. PDMS absorbs drugs, especially hydrophobic small molecules. Once a drug has been run through a chip, the PDMS is contaminated. Thoughtful experimental design prolongs the useful lifetime of a chip; e.g., test low concentrations of drugs before higher concentrations.
In a chip filled with a saline buffer and with no worm, the electrical signal should remain between 9uV and 20uV as displayed on the top left corner of NemAcquire.
A standard EPG (electropharyngeopgram) signal is composed of a positive peak (corresponding to the excitation of the pharyngeal muscle) and a negative peak (corresponding to the relaxation of the pharyngeal muscle). Although the overall shape of the trace can change due to visualization parameters and inter-individual variability, we found that the quantifiable parameters are often consistent within a population.
If the signal amplitude is small or not visible, there are several things you can do to.