Final answer:
The two main inhibitory neurotransmitters in the CNS are gamma-aminobutyric acid (GABA) and glycine, which are pivotal in maintaining neuronal excitability by causing hyperpolarization of neurons.
Step-by-step explanation:
The two main inhibitory neurotransmitters in the central nervous system (CNS) are gamma-aminobutyric acid (GABA) and glycine. GABA is synthesized from glutamate and is known for its role in decreasing neuronal excitability throughout the nervous system. Receptors for GABA include GABAA, GABAB, and GABAC receptors, with effects ranging from fast to slow inhibitory actions, largely including the influx of chloride ions which leads to hyperpolarization of the neuron. Glycine, acting similarly through its receptors, also causes hyperpolarization. While GABAergic inhibition predominates in the brain, both GABA and glycine serve as the primary inhibitory neurotransmitters in the spinal cord and brainstem. They are crucial for maintaining proper excitatory-inhibitory balance, which if disrupted, could lead to neuropsychiatric and ischemic conditions.