Flashcards in Adrenergic and Cholinergic Effects of CNS Drugs Deck (9):
BBB exists to maintain homeostasis in the environment surrounding neurons and to prevent neurotransmitters from escaping
BBB breaks down with aging
What kinds of conditions can cause temporary BBB breakdown?
- Post- MI leading to cerebral edema
- Following marked rise in BP
- After injection of hypertonic solutions
Structure of BBB
- Brain capillary endothelium with endothelial cells containing lots of metabolic enzymes to break down drugs
- Tight junctions between endothelial cells
- Astrocyte vascular feet processes
What gets through the BBB
Lipophilic molecules that are non-protein bound, un-ionized drugs, gasses, water
Evidence now shows that sub-concussive collisions in football players can can lead to disruption of the BBB integrity, leading to a surge in the astrocytic protein S100B in blood,
We knbow that lipophilicity is important for a drug to gain access to the CNS. How is it measured experimentally>
Octanol/Water partition coefficient...the higher the coefficient, the more easily the drug is absorbed
Why do lipophilic drugs have such long elimination times but such short durations of action
Long time for elimination because they are stored quickly in adipose tissue.
Short duration of action because they quickly distibute to a large volume of distribution.
Quick in Quick out...Quick to highly perfused organs (brain, heart, kidney) quick to perfuse out of them