Effects of amygdala cholinergic system on modulation of anxiety behaviors of rats by use of Elevated Plus Maze test

Anxiety is a common psychological disorder in the society which can be accompanied by physiologic and behavior disorders. There is evidence that neurons and cholinergic receptors are involved in the neurobiology of anxiety. In the present study, we have investigated the effects of muscarinic and nicotinic receptors of cholinergic system in amygdala of rats on anxiety, by use of Elevated Plus Maze test. In this study the locations of amygdale in the rats were determined by stereotaxis method and leading cannulas were inserted into the same locations for drug injection into amygdala. The effects of muscarinic and nicotinic receptors of central amygdala for controlling anxiety in the rats were assessed by use of Elevated Plus Maz test. Bilateral intra amygdala injection of physostegmine (2 µg/rat) decreased percentage of open arm time (OAT) and open arm entries (OAE) (p<0.05) which indicated an increase in the level of anxiety. However bilateral injection of the muscarinic receptor antagonist, pilocarpine (0.25, 0.5, and 1 µg), did not show a significant change in anxiety-like behavior (p>0.05). Bilateral administration of nicotine (1 and 2 µg/rat) into central amygdala (intra-CeA) induced an anxiogenic effect, shown by decreases in the percentage of OAT and percentage of OAE (p<0.05). Bilateral intra-CeA injection of mecamylamine (20, 30, 50 ng/rat), a selective nicotine acetylcholine receptor (nAChRs) antagonist led to a significant anxiolytic behavior in the rats (p<0.05). The results of this study indicate the muscarinic and nicotinic receptors of amygdale have a role in controlling anxiety.