Which neurotransmitter is the primary excitatory amino acid in the CNS?

Which neurotransmitter is the primary excitatory amino acid in the CNS?

• A. GABA
• B. Glycine
• C. Serotonin
• D. Glutamate

Answer: (D)

Neurons communicate in the CNS by signals that either excite or inhibit firing. The main excitatory transmitter that is an amino acid is glutamate. When released, glutamate activates ionotropic receptors (AMPA, NMDA, kainate), opening channels for Na+ and Ca2+ to enter the postsynaptic cell and producing rapid depolarization. This fast excitatory signal underpins most CNS excitation and also drives synaptic plasticity, especially via NMDA receptors, which is important for learning and memory. GABA is the primary inhibitory transmitter in the CNS, hyperpolarizing neurons through chloride channels. Glycine is another inhibitory transmitter, mainly in the spinal cord and brainstem, though it can modulate NMDA receptor activity. Serotonin is a monoamine neurotransmitter, not an amino acid. Thus, glutamate is the correct answer.

Neurons communicate in the CNS by signals that either excite or inhibit firing. The main excitatory transmitter that is an amino acid is glutamate. When released, glutamate activates ionotropic receptors (AMPA, NMDA, kainate), opening channels for Na+ and Ca2+ to enter the postsynaptic cell and producing rapid depolarization. This fast excitatory signal underpins most CNS excitation and also drives synaptic plasticity, especially via NMDA receptors, which is important for learning and memory. GABA is the primary inhibitory transmitter in the CNS, hyperpolarizing neurons through chloride channels. Glycine is another inhibitory transmitter, mainly in the spinal cord and brainstem, though it can modulate NMDA receptor activity. Serotonin is a monoamine neurotransmitter, not an amino acid. Thus, glutamate is the correct answer.