what causes the buzz high rush being with narc?

Goldie here on the forum in one of her posts mentioned how we get a buzz from staying in contact with the narc... can anyone explain what causes this buzz? I feel such a buzz a high a rush when I am with him that I do not feel with anyone else! Can you please explain why the narc makes me feel this way!? Also why is it that he cannot let go of me after 2 years he keeps wanting to see me for more sex no matter how long I keep him on block he will persist until he sees me again and then he will be all cold again until I guess he needs his next "supply"? Am I starting to understand the process? I hope to hear your thoughts soon, thanks again!