What is the function of Glutamine?

• A. Neurotrophic factor
• B. Primary excitatory neurotransmitter in CNS; involved in learning and memory
• C. Primary inhibitory neurotransmitter in CNS
• D. Slow-wave sleep regulator

Answer: (B)

Glutamine mainly serves as a reservoir and precursor for the brain’s major excitatory transmitter, glutamate. Through the glutamate–glutamine cycle, glutamine is taken up by neurons and astrocytes and converted into glutamate, which then drives excitatory signaling essential for synaptic plasticity, learning, and memory. The option that describes the function as the primary excitatory neurotransmitter in the CNS and its link to learning and memory reflects the key outcome of this metabolic pathway: glutamine supports excitatory neurotransmission by providing the substrate for glutamate, the transmitter that underpins these cognitive processes. The other choices don’t fit because glutamine is not a neurotrophic factor, it is not the primary inhibitory transmitter (that’s GABA), and it’s not specifically known as a regulator of slow-wave sleep.