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Endogenous brain angiotensin II disrupts passive avoidance behavior in rats
Neuroscience Letters
|September 1, 1979
Summary
Renin injection into rat brains significantly disrupted avoidance learning by increasing brain angiotensin II (ANG II) levels. These learning impairments were dose-dependent and reversible, highlighting ANG II
Area of Science:
- Neuroscience
- Endocrinology
- Pharmacology
Background:
- Angiotensinogen, the precursor of angiotensin II (ANG II), is present in brain tissue and cerebrospinal fluid (CSF).
- Renin can stimulate endogenous brain ANG II production.
- The role of brain ANG II in learning and memory requires further investigation.
Purpose of the Study:
- To investigate the effect of direct renin administration into the brain ventricles on avoidance learning in rats.
- To determine the impact of increased cerebrospinal fluid (CSF) ANG II levels on learning and memory processes.
- To assess the role of the renin-angiotensin system (RAS) in the central nervous system (CNS) in modulating cognitive functions.
Main Methods:
- Female Wistar rats were subjected to passive avoidance tests.
- Renin was injected into the lateral brain ventricles at doses of 0.01 and 0.1 units.
- Cerebrospinal fluid (CSF) ANG II levels, avoidance learning frequency, and latency were measured.
- The effect of the converting-enzyme inhibitor SQ 14225 was evaluated.
Main Results:
- Renin injection significantly increased CSF ANG II levels in a dose-dependent manner.
- A dose-dependent disruption of avoidance learning was observed, characterized by increased entry frequency and decreased latency.
- These learning deficits were statistically significant (P < 0.001) and persisted for over 24 hours.
- Administration of the converting-enzyme inhibitor SQ 14225 abolished the disruptive effects of renin.
- Renin injections administered after learning acquisition had no effect on memory recall.
Conclusions:
- Direct renin administration into the brain ventricles elevates brain ANG II levels and impairs passive avoidance learning in rats.
- The findings suggest a critical role for endogenous brain ANG II in modulating learning and memory processes.
- Inhibition of angiotensin-converting enzyme (ACE) can counteract the detrimental effects of increased brain ANG II on learning.