Which neurotransmitter is inhibited by caffeine's action?

Caffeine primarily acts as an antagonist of adenosine receptors, which means it effectively inhibits the action of adenosine in the brain. Adenosine is a neurotransmitter that normally promotes relaxation and sleepiness; it accumulates in the brain throughout the day and contributes to the feeling of fatigue. By blocking adenosine receptors, caffeine prevents these feelings of tiredness and promotes alertness and wakefulness. This antagonistic effect leads to increased levels of other neurotransmitters such as dopamine and norepinephrine, which further enhance mood and cognitive function.

While serotonin and dopamine are important neurotransmitters involved in mood and reward processing, respectively, they are not directly inhibited by caffeine. Instead, caffeine’s central role focuses on counteracting adenosine's effects, making it a crucial factor in understanding how caffeine influences energy levels and alertness.