Peptides and the senescent blood-brain barrier.

Peptides can influence numerous systems known to be altered by aging. They can affect the passage of non-peptide substances across the blood-brain barrier (BBB) and themselves can cross by both saturable and non-saturable transport mechanisms. The passage of peptides across the BBB is influenced by numerous physiological and pathological events, including aging. Taken together, the evidence suggests that alterations in peptide/BBB interactions may play a significant role in senescence.