What do barbiturates primarily affect in neuronal activity?

Barbiturates primarily affect neuronal activity by increasing the opening duration of ion channels, specifically the GABA_A receptor chloride channels. By binding to these receptors, barbiturates enhance the inhibitory effects of the neurotransmitter GABA (gamma-aminobutyric acid), which in turn prolongs the duration that the ion channels remain open when activated. This results in an influx of chloride ions into the neuron, leading to hyperpolarization, making it less likely for the neuron to fire an action potential.

This mechanism illustrates how barbiturates act as central nervous system depressants by amplifying inhibitory signaling, effectively leading to sedative, anxiolytic, and anticonvulsant effects. The understanding of this action is crucial in neurobiology since it highlights how drug interactions can modify neuronal excitability and overall brain function.