Which of the Following Is a Reason That Is It

Multiple Choice

Which of the following is a reason that is it is difficult to prove that amino acids can function as neurotransmitters?

A) Amino acids can be released from nerve terminals.
B) Postsynaptic receptor activation by application of amino acids can excite or inhibit neurons.
C) Amino acids are found within glial cells.
D) Amino acids play a role in protein synthesis for all nerve cells.
E) Amino acids are found within few cells of the brain.