Electromagnetic Field and Γ Aminobutyric Acid a Receptors Interaction in the Fear Response

Abstract

Freezing behavior is a fearful reaction to specific stimuli, most commonly observed by animals. One of the neurotransmission system most consistently linked with fear response is the GABAergic system, in which GABA through GABA_A receptor can influence fear response. The aim of the present investigation was to examine the effect of IP injection of muscimol (GABA_A agonist) and bicuculline (GABA_A antagonist) with and without EMF exposure on the frequency of fear response. Fifty adult male rats weighing 180-200 g were used. Animals were divided in ten groups, of which five groups were exposed to ELF-EMF for 30 days at 8 h day^-1 in a solenoid, creating an electromagnetic field of 500 µT by a 50Hz electrical current created. Animals were then treated with various doses of muscimol and bicuculline before being exposed to electrical shock. Each animal were received 100 electrical shocks every session. After shock induction, the fear response was determined by monitoring the reaction of shocked animals to a normal rat which was placed in the electroshock chamber. Data were analyzed by Mann-Whitney test and p<0.05 was considered as significant level. It was shown that injection of muscimol at 0.5 mg kg^-1 in group with and without EMF exposure, significantly decreased the frequency of fear response but muscimol at 2 mg kg^-1 only in group exposed to EMF significantly decreased frequency of fear response. Bicuculline significantly decreased frequency of fear response in group without EMF exposure, but it significantly increased the frequency of fear response in group with EMF exposure. Results indicated that interaction of GABA_A receptors and EMF exposure possibly involved in the modulation of fear response.