How does one consciously release adrenaline?

You can try making the CONSCIOUS decision to scare yourself half to death a lot. . . eg, if you're afraid of spiders, put your hand in a jar full of the buggers. Or if you're afraid of heights, go stand on the edge of a very tall building. If you're deathly afraid of public speaking, join the debating club . . . If you're scared of doing something, do it.

Exercise is also good.

Put yourself into a fight-or-flight frame of mind.

Note: I do not recommend this. It's an awful strain on the circulatory system. You could give yourself a stroke.

try doing more exercise...