Final answer:
GABAA receptors consist of 5 subunits, each containing 4 trans-membrane domains, and they play a significant role in the inhibition of neuronal activity in the central nervous system.
Step-by-step explanation:
The GABAA receptor is composed of 5 subunits, each with 4 trans-membrane domains. These ionotropic receptors are critical for mediating synaptic inhibition in the central nervous system by allowing the influx of chloride ions upon activation, which hyperpolarizes the neuronal membrane and decreases cell excitability. GABAA receptors are assembled from a variety of subunit isoforms that dictate the receptor's pharmacological properties, but they characteristically consist of five subunits that form a chloride ion channel.