Abstract
Behavioral and functional studies describe hemispheric asymmetry in anxiety and metabolic behaviors in responses to stress. However, no study has reported serotonergic receptor (the 5-HT(1A) receptor) lateralization in the basolateral amygdala (BLA) in vivo on anxiety and metabolic behaviors under stress. In the present study, the effect of unilateral and bilateral suppression of the 5-HT(1A) receptor in the BLA on anxiety, and metabolic responses to chronic restraint stress was assessed. Male Wistar rats 7 days after cannulation into the BLA received chronic restraint stress for 14 consecutive days. 20 minutes before induction of stress, WAY-100-635 (selective 5-HT(1A) antagonist) or sterile saline (vehicle) was administered either uni- or bi-laterally into the BLA. Behavioral (elevated plus maze; EPM, and open field test), and metabolic parameter studies were performed. Results showed that stress causes a significant increase in weight gain compared to control. In the non-stress condition, the left and bilaterally, and in the stress condition the right, left, and both sides, inhibition of 5-HT(1A) in the BLA reduced weight gain. In the restraint stress condition, only inhibition of the 5-HT(1A) receptor in the left BLA led to decreased food intake compared to the control group. In stress conditions, inhibition of the 5-HT(1A) receptor on the right, left, and bilateral BLA increased water intake compared to the stress group. Inhibition of the 5-HT(1A) receptor on the left side of the BLA by WAY-100-635 induced anxiety-like behaviors in stressed rats. Similarly, WAY-100-635 on the left BLA effectively caused anxiety-like behaviors in both EPM and open field tests in the control animals. In conclusion, it seems that 5-HT(1A) receptors in the left BLA are more responsible for anxiety-like behaviors and metabolic changes in responses to stress.