Neurotransmitter

Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

However, there are other materials, such as the zinc ion, that are neither synthesized nor catabolized (i.e., degraded; see Anabolism) and are considered neurotransmitters by some. Thus, the old definitions are being revised.