Injection of Biologically Active Substances into the Brain

Publisher Summary This chapter describes the injection of biologically active substances into the brain. The injection of biologically active substances into the brain is an important technique in the field of neuroscience. Injection directly into the brain can circumvent numerous problems associated with systemic delivery of biologically active compounds. The systemically administered agent does not readily penetrate the blood–brain barrier (BBB). Most of the brain is protected from the systemic circulation by the BBB. Quaternary amines, charged compounds, proteins, highly lipid- or water-soluble compounds, or cells that may be administered systemically would, therefore, not enter the brain readily. Direct injection, thus, affords probable access to brain parenchyma of compounds that would otherwise not enter the brain when administered by any other route. The systemically administered drug readily enters the brain, but peripheral actions of the drug complicate its study. This problem can be circumvented given that an agent that does not cross the BBB is available to antagonize the peripheral actions of the drug under study. However, barring the availability of such a compound, a selective CNS response can be obtained only when the agent is injected directly into the target structure.