Maybe this is normal for mice but the dose of ketamine used (5-20 mg/kg) seems high? I know mice metabolism is very different but that's in the range of a gram of ketamine for a normal sized human.
The mice may not have been depressed because it's hard to be depressed when you're in a k hole
I'm not sure what a typical ketamine dosage looks like, but I have discussed it with my psychiatrist as a fallback if TMS doesn't work out, and she said that ego death is one of the primary mechanisms (alongside reintegration therapy, spending a weekend tripping balls won't fix a thing - at least perpetually).
For humans the antidepressant dose is very low - I think less than 50mg. You might feel some minor dissociative effects at that dose, but only minor, yet in some patients it can apparently produce a pronounced antidepressant effect which is interesting and suggests a non NMDA mechanism
The mice may not have been depressed because it's hard to be depressed when you're in a k hole