Final answer:
Glutamate is the main excitatory neurotransmitter in the CNS, acting via the glutamatergic system and specific receptors like AMPA, NMDA, and Kainate to depolarize and excite the postsynaptic neuron.
Step-by-step explanation:
The amino acid neurotransmitter responsible for excitatory synaptic transmission is glutamate. This neurotransmitter operates through the glutamatergic system, utilizing specific receptors such as AMPA, NMDA, and Kainate to mediate rapid and direct depolarization of the postsynaptic cell, leading to an excitatory response. These ionotropic receptors allow Na+ and sometimes Ca2+ influx, which directly depolarizes the membrane potential. In contrast, GABA (gamma-aminobutyric acid) and glycine are amino acid neurotransmitters that lead to inhibitory effects by causing hyperpolarization of the postsynaptic neuron. The precise regulation of these neurotransmitters and their receptors is critical for proper brain function and prevention of excitotoxicity, which can lead to neurodegenerative disorders.