Many systemic sources may synthesize and release the neurotrophin
in blood as epithelial cells, vascular endothelial cells,muscle cells, activate macrophages and lymphocytes. Platelets store the major part of serum BDNF: difference between plasma and serum BDNF content is 1:20.
I appreciate the quantitaive information you give. NGF was discovered dalla Rita in the maxillary and submandibulary gland of the rat, which is the submandibular gland in us. Tsukinoki found stress-related increases BDNF etc.in the SMG ( http://www.ncbi.nlm.nih.gov/pubmed/23209335 ) and Mathison reveiws the many effects of SMG substances ( http://www.benthamscience.com/open/toinfj/articles/V002/9TOINFJ.pdf ). BDNF does not cross the BB easily. SO how much is from the SMG, and how much from the platelets?