Negro, you are absolutely wrong about getting high from injecting into an artery.
I have injected into an artery before myself and I can verify that information written about injecting into arteries is true.
Arteries are a means of the heart transfering blood directly to tissues in the body before the blood goes to the heart. It actually takes longer for the heroin to get to the brain and it becomes diluted in the tissues, so much in fact that you don't get high.
Heroin is an acid and burns the tissues. The tissues have more pain receptors than other parts of your body.
It's EXTREMELY painful. The process of injecting hurts and you'd be lucky if you could finish giving yourself a shot without having to pull out. Although I did manage to give myself an entire 50 unit shot.
The area around the injection will SWELL, turn red, burn and itch. In my case, my arm from my elbow to finger tips swelled up, turned red and inflamed, itched and burned. I did not get the slightest bit high and ended up having to call the hospital fearing I'd have to get my arm amputated. Fortunantly, I was able to reduce the swelling by wrapping a hot towel firmly around my arm.
Was someone to hit an artery in their neck, the neck could swell to the point that the user would suffocate.
So whatever you do, DON'T inject into an artery or even risk doing such. You won't get high. It's exceptionally painful. You may die.