Final answer:
Postsynaptic stimulation/blockade affects tonic DA signaling by influencing the overall dopaminergic tone, while phasic DA release is characterized by burst releases modulated by presynaptic actions of drugs. Tonic DA levels moderate baseline excitability, and phasic releases are responses to stimuli regulated at the presynaptic level.
Step-by-step explanation:
Your confusion is understandable, given the complex mechanisms involving dopamine (DA) signaling in the brain. When the Frank & O'Reilly (2006) paper mentions that postsynaptic stimulation/blockade affects tonic DA signaling, it refers to the relatively constant and consistent level of neurotransmitter presence in the synapse or extrasynaptic regions. Tonic signaling often involves the regulation of DA receptors and transporters on the postsynaptic neuron and can exert an influence on the overall dopaminergic tone present in certain brain regions.
In contrast, phasic DA release is characterized by brief and high-frequency bursts of neurotransmitter release, in response to specific stimuli or events. These bursts are traditionally associated with reward prediction and are modulated by the presynaptic action of drugs, such as presynaptic auto-receptor regulation or by influencing the amount of DA that is released during each burst.
To further illustrate, tonic DA levels modulate the baseline excitability of dopaminergic neurons and are sensitive to postsynaptic neuronal activity. Whereas, phasic DA release results from presynaptic neuronal firing patterns (such as bursting activity of DA neurons). Therefore, drugs that affect presynaptic mechanisms can adjust this release pattern, shaping the phasic response without substantially affecting the tonic background levels of dopamine.
If you're looking for literature to expand your understanding, the following articles may offer valuable insights: Grace (1991) for foundational knowledge on DA signaling modulation, and more recent reviews like Cools (2011) and relevant chapters in textbooks on neuroscience may provide updated discussions on tonic versus phasic signaling.