Do Angiotensin Peptides Improve Memory? A Systematic Review of Animal Studies

In this systematic review of 32 animal studies, angiotensin IV (Ang IV) improved cognitive performance in 7 of 11 studies in normal animals and 8 of 9 studies in cognitively impaired models. Ang IV and its analogs (including dihexa and Nle1-Ang IV) enhanced spatial working memory, passive avoidance, and object recognition. Angiotensin-(1-7) benefited memory in 2 of 3 studies and showed anti-dementia properties. The peptides were most effective when delivered directly into the brain (intracerebroventricularly) close to the time of learning or memory testing.

The researchers conducted a systematic review of experimental (non-human) studies, searching databases and identifying 450 articles. Of these, 32 met inclusion criteria. Studies were categorized by peptide type (Ang IV or Ang-(1-7)), cognitive test (passive avoidance, spatial memory, object recognition), and whether animals were normal or cognitively impaired. Results were synthesized narratively.

Dementia and cognitive decline affect tens of millions of people, and effective treatments remain elusive. This systematic review reveals that two peptides from the brain's own renin-angiotensin system can improve memory and learning in animal models — including models of cognitive impairment. The connection between blood pressure peptides and brain function is an underappreciated research area that could yield new treatments for Alzheimer's disease and other dementias.

Most dementia research focuses on amyloid plaques, tau tangles, or neurotransmitter deficits. The finding that the brain's renin-angiotensin system directly influences memory opens a completely different therapeutic avenue. Dihexa, an Ang IV analog, has attracted particular interest as a potential cognitive enhancer. The connection also raises questions about whether common blood pressure medications (ACE inhibitors, ARBs) might affect cognition — positively or negatively.

All 32 studies were in animals, primarily rodents, so translation to humans is uncertain. Most studies used intracerebroventricular delivery (directly into the brain), which isn't practical for human treatment. The review could not perform meta-analysis due to heterogeneity in study designs. Sample sizes of individual studies varied. Only acute (single-dose) administration was studied in most cases.