On the interpretation of results obtained in singly housed animals

I had been warned: “use a thick glove and grab it as fast as you can. ” Five minutes later, I was chasing the animal all over the place in the laboratory. As soon as the cage lid was lifted, the rat had jumped out of the cage to escape. This was my first encounter with a chronic “epileptic” rat many years ago—a stressful one for me. But I had not realized that the animal was far more stressed than I was. For those of us using chronic animal models of epilepsy, we often experience this situation. We can see that the animal is afraid and aggressive. But I never questioned why this was the case. I always assumed that it was a consequence of “epilepsy,” of the lesions provoked by kainic acid– or pilocarpine‐induced status epilepticus, just like other classical phenotypic traits reported in these models such as a depression‐like behavior and cognitive deficits. We just had to deal with it. This was manageable when we were performing 24/7 recordings with a wireless system. But it became an issue to consider when we decided to use silicon probes in chronic animals. In a control animal, it is already not that easy to connect the cable to the preamplifier fixed on the head, which requires some strength. The animal needs to remain still. A chronic animal, remaining still? Even Ethan Hunt would have hesitated to accept this mission impossible. Pascale Quilichini had finished her postdoc in Gyuri Buzsaki's lab, and her citizens united for research in epilepsy taking flight project involved recordings with silicon probes in epileptic animals. I was there to help with the first connection attempt. When she lifted the lid, the rat came to be scratched, play with Pascale, and waited to get the fruit loop. It remained still during the connection. Hold on. A pilo rat? No way. Status epilepticus must have failed to trigger epileptogenesis. But no, the animal had spontaneous seizures. What was the difference? In Gyuri's lab, each animal becomes a friendly pet, as interactions between the animal and the experimenter can last several weeks. She had done the same thing, building a relationship well before triggering status epilepticus, and when the animal recovered, the friendly relationship was still there, as daily interactions and play continued. Well, that was making our life more comfortable, and I did not think further than that. Later, we looked at the consequences of past stressful situations on the development of epilepsy and comorbidities. Although animals were singly housed for wireless recordings, they had daily interactions with experimenters. The control group (not stressed) had a very low seizure frequency and no comorbidities, in contradiction with our past results, and those from many colleagues.1,2 This is when I associated stress, phenotype, and housing conditions. If housing conditions can have such a strong effect on the phenotype, what does it mean for the interpretation of the results obtained from socially isolated animals? But I had to convince myself, and thus perform a dedicated study. All grant attempts failed. A recurrent comment was that decades of research have shown that single housing is stressful for rodents, which are social animals. True, but my question was, what does it mean in epilepsy research? Since I am stubborn, I decided to do the study nevertheless. Once the study was completed, convincing the reviewers and reviewing editor was not easy, but their comments were constructive and forced us to go far beyond what we wanted to do. At the same time, I decided to change the reporting of the results using estimation statistics (https ://www.eneuro.org/conte nt/6/4/ ENEURO.0259-19.2019). The combination of these independent factors allowed us to learn two important things.3