Dopamine is released in the brain primarily through a process called exocytosis, triggered by action potentials (electrical signals) in dopamine- producing neurons. The release happens when dopamine stored in vesicles inside neurons is ejected into the synaptic cleft, the space between neurons, to communicate with other nerve cells. Key points about dopamine release include:

• It is typically released in response to neuronal firing (action potentials), which cause vesicles to fuse with the cell membrane and release dopamine quickly within milliseconds.
• Dopamine release can also occur in smaller amounts without action potentials, known as tonic transmission.
• Dopamine release is involved in signaling motivational salience, influencing behaviors related to rewards and motivation rather than just pleasure alone.
• The release occurs in specific brain pathways, such as the nigrostriatal pathway (motor control) and the mesolimbic pathway (reward processing).
• Dopamine release increases with anticipation or experience of reward-related stimuli like food, sex, shopping, or even during meditation.
• The level of dopamine released can vary depending on different factors including neuronal activity and external stimuli.

In summary, dopamine is released predominantly when neurons fire action potentials, but can also be released tonically in small amounts, playing a major role in motivation, reward, and motor functions.