yes there are tests to measure these things. they show up in blood work panels. here in america blood work is a normal routine part of seeing ones own medical doctor. Spinal taps are another test that these chemicals show up on, MRI's can also show a doctor how the brain is functioning and if the neuro transmitters/ receptors, are working correctly.

I have these tests frequently due to my having MS, and other medical and mental problems.

my suggestion is talk with your treatment providers, they can show you what a blood work panel is and what each of those letters stand for on the panels and which tests are the ones that show them how much of what chemicals are in your body, brain, spine and throughout your body.