Yes, DEPRESSOR is a Scrabble word!

Letter values in Scrabble US: D 2, E 1, P 3, R 1, E 1, S 1, S 1, O 1, R 1.

Is it a valid word?

DEPRESSOR is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any skeletal muscle that draws a body part down
any nerve whose activity tends to reduce the activity or tone of the body part it serves
a device used by physician to press a part down or aside

Also: depressor muscle, depressor nerve.