Interesting question as I am working on the BBB. However, the BBB itself is a part of the layers that represent the brain cells. BBB consists of the endothelial cells, astrocytes, pericytes, etc. Which cells are you planning to cross, and which cells you would like to target?

Thanks Nurul. The target is located in the extracellular fluid present in brain tissue, but I don´t want the compound to get into neurons or glia, but rather to remain in their extracellular aqueous milieau, where it would interact with its peptide-target. Any suggestions will be appreciated.

It would seem that you need 2 things, 1, to get into the CSF directly, and 2, to have a drug that is not going to get into neurons or glia. It is likely that anything that crosses the BBB is going to get into neurons or glia. For 1, I'm not sure of a way around a chronic cannula into the lateral ventricles, or some other access point to CSF in the brain. A chronic icv cannula attached to an external pump (like a subcutaneous alzet minipump) might be something to look into if you need a chronic administration. The key to 2 would be to have a drug too large and or cumbersome to get into cells.

Thanks Benjamin, I like your secon suggestion: ".. the key to 2 would be to have a drug too cumbersome (or anything but large) to get into cells.." . Further suggestions along this line by any reader will be most welcome. For the time being, the nasal route of administration will be preferred. Nasal administration has proved successful in a number of cases (including peptides) and of course less traumatic than intracerebral. Cheers.