Barbituates primarily result in what change within the brain?

Barbiturates primarily function as central nervous system depressants, which means they significantly decrease neuronal excitability and overall brain activity. When barbiturates are ingested, they enhance the effect of the neurotransmitter gamma-aminobutyric acid (GABA) at GABA-A receptors. This enhancement leads to increased inhibition of neuronal firing, resulting in a decrease in neurotransmitter activity across various neural pathways.

Due to their depressant nature, barbiturates can induce sedation, anxiolysis, and even anesthesia, which directly correlates with decreased brain activity in areas involved in arousal and alertness. Hence, the primary outcome of barbiturate use is a decrease in neurotransmitter activity, supporting the correct answer to the question.