re: your comment 'how do you stop anything in the brain - cut the brain out ?' No, you can still design chemicals and peptides that could cross the blood brain

re: your comment 'how do you stop anything in the brain - cut the brain out ?' No, you can still design chemicals and peptides that could cross the blood brain barrier via adsorptive endocytosis, saturable transporters and trans-membrane diffusion. Drug Delivery to the Brain: https://en.wikipedia.org/wiki/Drug_delivery_to_the_brain https://en.wikipedia.org/wiki/Drug_delivery_to_the_brain Modes of Transport: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697631/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697631/