Mouse Practical

So as you might know, I currently do translational research in ophthalmology, and clinical research at the Eye Institute. The translational research is one step ahead of basic science research, and I must say, I do not miss mixing buffers and making gels and reagents! I do all of my experiments of already genetically engineered mice--kind of like clinical trials for animals. I know that upsets some people, but the fact is that medicine would not be possible without it.

I did two years of mouse breeding and husbandry during undergrad, so I'm not stranger to mice. The mice I used to work with in the Comparative Biochemistry/Nutritional Science lab at Berkeley were large, mean, and aggressive. They would bite and injure each other to the point of death. The mice we work with currently are bred to be smaller, fat, and progressively blind (mirroring a human disease I'm studying). I much prefer them.

Anyways, my lab manager thought it would be a good idea for me to take a refresher animal handling course two weeks into my research. I rolled my eyes and signed up through the Animal Resources office. After getting through multiple doors with my hand scan access (which I'm terrible at, and takes me like 12 tries per door), I ended up at some basement of a building.

I was fifteen minutes early, as I try to be on most days. So to pass the time, I went around the room and examined the mice we were to practice on. They were all albino mice that looked like miniature rats in their individual cages, with various syringes and test tubes at each station. There were a few that were scuttling frantically in their cages. There was one that was jumpy. There were ones that were quite large. I passed on those (I wear a XS-S size glove). I finally came upon one that was smaller, calm, and looked sleepy. Perfect. I stood in front of that station.

As more people in lab coats signed in to take the course, I cataloged each one in my mind. Among the seven, I was the youngest by far. One woman had a hospital badge that said "Doctor" and I felt bad for her that she couldn't send her minions to do her bidding instead. Or she might've been starting up a lab herself, and needed the certification. There was a wiry, curly haired man wearing the thickest frames I'd ever seen. I gave him a backstory as a nerdy PhD student who doesn't get out much. There was a much older man who just stood by his cage and crossed his arms. The instructors wore masks (why didn't they give us masks?!) and demonstrated in the middle of our circle of mouse stations.

We went through the basics--how to sex the mice, how to pick them up by the base of their tails, how to scruff them. The scruffing (picking it up by the skin behind its ears to secure a hold in your palm) is the fun part, but some might consider it terrifying. There were lots of indignant yelps from all sides of the room. I did my work quietly and repeated it to make sure I knew I could do it with both hands.


The instructors then collected everyone's mice to put under a heat lamp for blood vessel dilation. I inwardly sighed that my small, well-behaved mouse was taken away before I could even do any procedures on it. What I got back in exchange was a large 48-gram mouse that kept trying to bite me. Great.

Then it got bloody. There is such a thing as a special trademarked lancet made to puncture the submandibular artery of the cheek ("Painless! Consistent! 1/2 mL per second! Safe!") and let me just say, it was the bloodiest mess I'd ever seen. You poke and it literally spurts blood faster than you can collect it in a test tube. The instructors said, "Okay, now you try." I couldn't bring myself to do that to my mouse. Did I mention it's a non-anesthetized procedure? 
 
Then we anesthetized them, which is an easy intraperitoneal needle jab of a ketamine/xylazine mix. This is where PhD boy raised his hand and said, "Uhm, can I get a new mouse? Mine died." The instructors said, "Who else killed their mice? We have extras." Hands went up. I tried hard not to laugh at how terribly morbid and strange the entire situation was.

The mice "went down," or fell asleep within minutes. This is where in my own lab, I would trim the whiskers, give them gel eye drops to keep their eyeballs moist, and gently wrap them in gauze on a heating pad so they won't become cold (did you know that mice can develop cataracts within 30 minutes of cold exposure?). But not during this practical. The instructor demonstrated saline injection into the tail veins. She couldn't get it done. She kept jabbing and jabbing and saying things like, "Oh my, I'm showing you a poor example. Let me try again. Oh no, I'm not doing it well, am I? Okay well you try." I picked up the thin 30 gauge IV needle. My blue vein flushed clear on the first try.

We then did a retro-orbital bleed. You basically cram a broken glass capillary tube into the eye socket of a mouse, and blood comes out. I skipped that procedure also--we're not in the business of collecting eye blood (just eyes, actually). The mice also got a teeth trim for those malocclusions, and ear punches for identification. PhD boy somehow managed to kill his third mouse doing these non-painful procedures, and so I mentally demoted him to high schooler. I later find out he's a "Research Specialist." Yeah, right.

Then there was the cardiac puncture. It's a terminal procedure, and so it happened last. The instructor showed us how to palpate for the xyphoid process and then stab deeply with a thick needle. You're basically stabbing the mouse's tiny heart from the outside and drawing blood directly from it. I found the spot, inserted, drew blood, and the mouse kind of shuddered and died. I quickly dislocated the cervical spine, because that's the humane second step in euthanizing mice. I stood wordlessly at my station for twenty minutes as my adult faculty classmates struggled and shrieked and sweated and poked their needles around.

An instructor finally came by and examined my work. She said, "Good job! Now let me show you how to dislocate the cervical spine." I said, "I already did." She let me sign out early, turned to the class, and said, "Who wants another mouse to practice on?"