Anxiolytic-like effect of losartan injected into amygdala of the acutely stressed rats

It has been recognized that the stress-related peptides are involved in anxiety states. angiotensin ii receptor blockade by systemic administration of the at1 receptor antagonists has been proposed as a new treatment possibility for anxiety disorders. for better understanding of the related mechanisms,in this study we evaluated effects of bilateral intraamygdaloid injections of 2 (los 2) and 4 (los 4) μg of losartan (los),a selective at1 receptor antagonist,on the behavior of the not stressed and acutely stressed rats in an elevated plus maze. under non-stress conditions,los 4 increased time spent in the open arms (p < 0.01),number of extreme open arm arrivals (p < 0.05),time per entry (p < 0.01),and the number of total arm entries (p < 0.05) showing thus considerable anxiolytic activity. the open arm extreme arrivals were increased by los 4 in both not stressed (p < 0.05) and stressed (p < 0.05) rats. when no stressed and stressed los 4 animals were compared,time per entry and the number of closed arm entries (p < 0.05,both) were decreased in the latter group. moreover,the los 4 stressed rats had significantly increased open/closed arm quotient (p < 0.05) as compared to the both control and los 4 non-stress group (p < 0.05,both). these findings suggest that the at1 receptor blockade in amygdala is important for the anxiolytic action of los (and probably other at1 receptor blockers) under both non-stress and stress conditions. copyright © 2012 by institute of pharmacology polish academy of sciences.