Back ground & aim: In the recent years, the increasing use of electronic devices which generate electromagnetic fields, focused researchers’ attention to investigate the electromagnetic fields effects on human health. Therefore, the purpose of the present study was to investigate the effect of prolonged exposure to extremely low frequency electromagnetic fields (ELF) on the adrenergic system in the small intestine of male rats.

Methods: In the present experimental study, 21 Adult male rats (wistar) were divided into three groups: experimental group, which were exposed to ELF (50Hz, 1mT) for 75 days, the sham-operated group, which were kept in similar conditions exception Off solenoid and the control group, which were kept in normal conditions. After 75 days, the rats were anesthetized by intra peritoneal injection of pentobarbital sodium (50 mg/k). Then, the ileum tissue was dissected and divided into 1 cm strips. The strips were placed in organ baths containing oxygenated, pH=7.4 Krebs solution. Furthermore, the mechanical activity of the tissue was recorded with force transducer of bridge amplifier which was linked to A-D Instrument power lab in response to Phenylephrine(4 ×10^{-6 M). Data was analyzed using one way ANOVA test.}

Results: Relaxation changes of isolated ileum tissue was displayed in two ileum strips with same length and in the same animal, According to the obtained results, the ileum relaxation in exposure to ELF (experimental) compared to the control and sham groups significantly increased (p&le0.05). Accordingly, the relaxation changes of ileum in response to the phenylephrine at different times and after deducting the basic tension represented a significant increase (p&le0.05) of Ileum relaxation in the experimental group compared to the sham and control groups.

Conclusion: It can be concluded that prolonged exposure to extremely low-frequency electromagnetic fields may lead to increase of  the &alpha₁-adrenergic receptors sensitivity.