Effect of prolonged exposure to low-frequency electromagnetic fields on the interaction of nitrergic and cholinergic systems in the isolated rat trachea

Nitric Oxide is an important endogenous compound that acts as bronchodilator in trachea. Electromagnetic fields (EMF) affect nitric oxide level in different tissues. The interaction of nitrergic and cholinergic systems in airways has been reported. Therefore, the present study was performed to evaluate the interaction of cholinergic and nitrergic systems in the trachea of rats that have been exposed to EMF. Adult male rats were divided into 3 groups: experimental group was exposed to 1 mT (militesla) EMF for 135 days, sham group was kept in the same condition but in off solenoid and control group was kept in normal condition. After 135 days, the mechanical response of transverse rings of isolated trachea to acetylcholine in the absence and presence of L-NAME, an inhibitor of nitric oxide synthesis, were recorded using PowerLab-AD system. The results showed a significant increase in cholinergic contractions of trachea in the presence of L-NAME in control and sham groups (P< 0.05). However this enhancement of contraction was not detected in EMF exposed group. It can be concluded that nitric oxide has a modulatory effect on the airway cholinergic contraction, however this modulation is inhibited by prolonged exposure to EMF.