Table 1.

Troubleshooting

Potential Problems	Commentary
Animals remain in the brightly lit start chamber and do not exit onto the probes after 30 s	This may occur a few times during testing, particularly at the highest probe heights. In this case, an animal should be placed back into the home cage and the latency to exit onto the probes will be 30 s (max time). However, animals that do not exit the start chamber in the absence of the probes (0 mm) during baseline testing can be removed from study. If the majority of the animals do not exit the start chamber in the absence of the probes (0 mm), it may be necessary to adjust the brightness of the bulb (contact the manufacturer). This was not a problem in Pahng et al., 2017, but some adjustments to test parameters would need to be made if this problem occurs (consult with Coy Laboratory Products Inc. before making adjustments that may damage the equipment).
Animals do not place all four paws in the nociceptive probe chamber	In some cases, animals may not initially place all four paws in the nociceptive probe chamber. This behavior of testing the probes with the front two paws and sometimes all but one paw before proceeding is common. It is essential that the ‘latency to exit onto the probes’ is only measured when animals place all four paws and thus full body weight on the probes.
Animals do not enter the dark chamber after 60 s or only partially enter the dark chamber	In this case, an animal should be placed back into the home cage and the latency to enter the dark chamber will be 60 s (max time). If animals only partially enter the dark chamber, then leave the animal alone until the 60 s has elapsed or the animal has placed all four paws in the dark goal chamber, which is the ‘latency to enter the dark chamber’ measure.
Animals enter the dark chamber after 60 s, but are in the way of closing the guillotine door.	Sometimes animals may have all four paws in the dark chamber, but the animal’s backside is in the guillotine doorway. In this case, the door should be closed slowly to avoid startling the animal. Fortunately, there is space under the chamber doors so there is room to close the door without the animal’s tail being caught.
Animals return to the light chamber after entering the dark chamber	This is less common, but still possible. This behavior is most likely to occur during training and is indicative of exploratory behavior, which should decrease over the course of training.