Spatial relationship between dopamine release sites and receptors

SPATIAL RELATIONSHIP BETWEEN DOPAMINE RELEASE SITES AND RECEPTORS 

The definition of a synapse requires at least the presence of a presynaptic element containing a concentration of vesicles and an apposed postsynaptic element, from which it is separated by the synaptic cleft (Peters et al., 1991). The vesicles of the dopamine synapses are concentrated around the points of synaptic contact rather than around the mitochondria that are part of the varicosities, so the release is probably punctate from the synaptic active zones. Notwithstanding the existence of synaptic specializations and 

An alternative estimate of the density of dopamine terminals could, in principle, be obtained from counting varicosities and correcting for the fractions of varicosities without synapses, and the fraction of synapses not on varicosities. Doucet et al. (1986) estimated an average density of dopamine varicosities of 0.1 pm-3. This number is remarkably close to the density of synapses estimated above. 

---