R. M. Wadsworth
Thanks for your comments.
According to published data, L-NAPNA is selective for neuronal NOS by virtue of selective accumulation within neurons. We have not carried out experiments of our own to verify the selectivity of this compound. However, that is not a crucial point for us, since the preparations that we use have all been endothelium denuded.
Your second point is very interesting: clearly it will depend on the physiological conditions. If there is flow through the artery, then endothelium output of NO will be increased. If there is high physiological tone in the nerves originating in the sphenopalatine and otic ganglia, then neuronal NO would be greater. Unfortunately, we do not have good data about either of these parameters for the cerebral circulation, so far as I am aware.
With best wishes,