Feel free to comment if you want, but whew. I've settled it. Here's an update; in case anyone wants to know:
I decided not to take the course. I spoke with the professor to help make my decision, and she said that most of the experiments we would be running would be behavioral ones - but there would be a stereotaxic surgery, after which the rats would be euthanized. I can dissect a dead rat; I can run behavioral tests on rats; and I know I would be fascinated and gain a lot from doing so. But I would feel absolutely horrible if I killed a rat, possibly even indirectly.
I currently haven't researched much about animal experimentation - but I know that often is difficult to apply animal research to humans, especially on non-primates; often animal lives are just wasted. And I just imagine, years from now, thinking back to when I killed animals... ugh. I know I could do it. But I also know that at my heart I am an animal lover who likes rats, who has volunteered at animal shelters, and who has kept many small rodents as pets - it would be incongruous of me to kill rats.
How sacred is life, I wonder. People have struggled with this argument with abortion, killing for the good of many, capital punishment, assisted suicide, etc etc. Why do we struggle so hard to live and let others live? The rats will die anyway - another student will take my place in this class and the rat I would've killed will be killed by this person. What does it matter? Does guilt matter? Do we overrate life because life is all we know? There are so many issues here; I won't even get into my confused thoughts on life/death.
Sure, this is a kind of sizable missed research opportunity. Sizable as in, in my tiny life as a psychology major. But I'll find another lab, do research that doesn't make me feel like a horrible person. She said she'd let me visit her lab if I want; show me around sometime. That's cool. Maybe I won't take her up on it, though. Not sure. I do feel a bit hypocritical for supporting animal research, being emotionally able to do animal research, and yet not doing it when it benefits me to do so. But I also would feel hypocritical doing it. I'm trying to live my life so later I won't regret the things I did or did not do, so... this is a small, uncertain step in that direction.
TLDR; I'm not going to do any animal experimentation! No use being wishy-washy about it; since I've unregistered from the class. And yet, inevitably, I will continue to be philosophical (AKA wishy-washy) about it.