52 y/o here. I have no clue what my T levels were when I was 24, but I am postive they never broke 800.
Now that I am convinced you aren't just claiming to be off T, I have given your issue some thought.
First, from personal experience, low D is a killer. I felt crappy, and taking 10,000 IU's of D made me feel 100% better in just a week. You can get a blood test to see where you D is at. You want to shoot for mid-range. Turns out Vitamine D plays a role in dopamine too:
http://www.livestrong.com/article/33...-for-dopamine/ But Vitamine D is toxic, so you don't want to do D if you have high D already. Try taking 5,000 IU's everyday for a week. No change, then not much point in continuing unless you get a blood test done and you are deficient.
Not much info on regerating dopamine receptors unless you are a salmander or a rat. And those articles were pretty useless.