Abstract
It is presumed that life on Earth has evolved in the presence of natural and ubiquitous magnetic fields. It is not surprising that biological systems can respond to a wide range of static magnetic fields (SMF). It is suggested that some physiological responses seem to be mediated through the nervous system. For weak intensity SMF, the effects of geomagnetic activity on the arterial baroreflex (reflex initiated by receptors in the aortic arch that alter peripheral vasomotion) in conscious animals were investigated by measuring blood pressure and microcirculation. Baroreflex sensitivity (BRS) was assessed as an indicator of cardiac autonomic regulation on the basis of the heart rate/mean arterial blood pressure relationship during a vasodilator (sodium nitroprusside) or a vasoconstrictor (phenylephrine) treatment. This study suggests that the geomagnetic field directly modifies microcirculatory responses related to BRS. These findings may have serious implications for individuals with ischemic diseases during periods of intense geomagnetic activity or geomagnetic storms. Concerning the moderate intensity SMF effects, pharmacological procedures and experimental animals have been used to assess the sympathetic responsiveness to SMF. We have reported that continuous exposure to moderate intensity SMF for several weeks can depress or suppress the action of sympathetic agonists (norepinephrine, phenylephrine, and dobutamine) and a sympathetic antagonist (reserpine) on hemodynamics and/or blood pressure by modulating sympathetic nerve activity or BRS in animals. In contrast, in humans there is little evidence to suggest that the SMF exposure of up to 8 tesla can alter blood pressure. Thus, this review describes the SMF effects (and non-effects) on the blood pressure in animals and humans.
Keywords: Static magnetic fields, geomagnetic activity, sympathetic nerve activity, baroreflex sensitivity
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