Fig. 4.
Predicted steady-state NO concentration profile at a synapse. (A) The NO sources are assumed to be a 7 × 7 array of NOS molecules, each producing 20 NO molecules/s (based on the initial rates of NO formation reported by Santolini et al. [114] after correcting for temperature). Each NOS molecule is assumed to be 100 Å (10 nm) in diameter [171]. Contour lines show NO concentrations of 0.5, 0.75, 1, and 2 nM NO. (B) Contour lines shown in (A) for the position perpendicular to the plane of the synapse (with an additional line at 0.25 nM NO) are superimposed on an electron micrograph of a typical excitatory synapse (from [115], reprinted with permission from AAAS; panel modified from [45]).