Final answer:
GABA is a direct neurotransmitter that opens ion channels and alters membrane potentials. Indirect neurotransmitters function by activating intracellular signaling pathways.
Step-by-step explanation:
GABA (gamma-aminobutyric acid) is a neurotransmitter that functions directly by binding to its receptors and opening chloride ion channels. This leads to an influx of chloride ions into the postsynaptic neuron, hyperpolarizing its membrane and making it less likely to fire an action potential. In contrast, neurotransmitters that function indirectly do not directly open ion channels. Instead, they bind to receptors and activate intracellular signaling pathways that ultimately lead to changes in membrane potential or synaptic strength. Examples of neurotransmitters that function indirectly include dopamine, serotonin, and norepinephrine.
Learn more about neurotransmitters