|A default Neurotransmitter|
|Size||0.5 to 5 nanometers|
|Role||Nerve impulse messengers|
Neurotransmitters are the recurring characters in Once Upon a Time... Life. Their main task is to send the messages along nervous system and enable the receiver to perform an action.
The series has introduced several different Neurotransmitters, yet there is always one constant main design. This design is worn by the Neurotransmitters usually seen in the episodes. They have short and slender humanoid figures with thistle complexion. They have long tails protruding from the back of their heads that reach their knees. They wear white, up-to-chest tights with two orange buttons on front.
The series featured almost identical type of Neurotransmitter, but as an anthropomorphic bear lacking the back antenna as well.
Other Neurotransmitters took appearance on various shapes and objects, depending on their use.