Huh, I didn't know that. It might be worth a try, but then I'm not certain that what repels dogs would also repel rats, and I have actually never noticed something like that in the rodents section of pet stores, though I might have overlooked it. Also I'm always cautious about chemical substances or even things like "harmless" aromatic oils/essences, because rats are quite prone to respiratory problems, not just infections but also allergies/irritation, for example you need dust free bedding/litter so normal normal wood-shavings stuff is bad, also it is said that the phenols from certain types of wood like pine or cedar (which are aromatic and thus often preferred because they cover the rodent smell) are toxic for rats or even rodents in general and may cause health problems with long exposure, though that may be less problematic in a brief exposure to a repellent. It highlights the problems though. Up to now I've thought more along the lines of getting some kind of plastic cover, though normal cable duct wouldn't work as I can't remove them from the wall to get them inside. But thanks a lot for the suggestion.