Final answer:
The most commonly found neurotransmitter in the brain is glutamate, which is integral to excitatory synaptic transmission and involved in functions like learning and memory.
Step-by-step explanation:
The most commonly found neurotransmitter in the brain is glutamate. It is the main excitatory neurotransmitter in the central nervous system (CNS) used by around half of the neurons in the brain. Glutamate is involved in critical brain functions such as learning and memory and plays a significant role in the regulation of development and creation of nerve contacts. This neurotransmitter is derived from glutamine and operates by binding to specific receptors, such as ionotropic and metabotropic receptors, which modulate excitatory synaptic transmission.
Other neurotransmitters like GABA, dopamine, and serotonin also play significant roles within the brain. For example, GABA is known for its inhibitory effects on neurons and dopamine is involved with responses in neurons that bind to a G-protein-linked receptor, affecting long-term neuronal responses.