What's the relation between firing of dopaminergic neurons and dopamine dispersion in terms of neurophysiological processes? Question: How does the firing of dopaminergic neurons affect the dispersal of dopamine?

Evidence of my limited familiarity with dopaminergic neurons and motivation for asking the question: 
Most of what I know about dopamine and dopaminergic neurons comes from reading papers on reinforcement learning and its possible neuronal implementation. I was surprised to see that (if I've understood correctly) firing of dopamininergic neurons might encode an error signal like the one propagated in simple temporal-difference learning (like in Schultz et al. 1997), while dopamine itself seems not to be involved in such basic aspects of learning but instead in higher levels of hierarchical reinforcement learning, like constructing representations of the environment found in model-based RL to be used in executive functions and generalizing and applying learnt information in novel tasks. I suspect that firing of dopamininergic neurons affects the dispersion of dopamine , but I'm not sure if my suspicion is the result of a misunderstanding.

Hypothetical context for an answer in case the question is too broad:
I'm imagining a group of dopaminergic neurons, some with axons extending to some brain region A and others with axons extending to brain region B. Say the neurons with axons extending to brain region A fire more than the others. This means they will produce more dopamine, and I suspect more dopamine will be present in A, but I'm having trouble finding supporting evidence.
I've mostly figured it out now, and I've a better idea of the words and phrases I need to search to get the information I was asking for.

The short answer comes from wikipedia: "The neurons' somata produce the enzymes that synthesize dopamine, and they are then transmitted via the projecting axons to their synaptic destinations, where most of the dopamine is produced." The transmission is a direct result of the firing of the neuron, so DA is dispersed, in the areas where dopaminergic axons end, proportional to the firing of the neurons.

A more complete answer would involve an understanding of the difference between tonic and phasic transmission, for which this has proved an informative and accessible source.

The above sources support the suspicion I mentioned in the hypothetical context provided in the question.