Sex and estrous cycle differences in the behavioral effects of high-strength static magnetic fields: role of ovarian steroids

Abstract

Advances in magnetic resonance imaging are driving the development of higher-resolution machines equipped with high-strength static magnetic fields (MFs). The behavioral effects of high-strength MFs are largely uncharacterized, although in male rats, exposure to 7 T or above induces locomotor circling and leads to a conditioned taste avoidance (CTA) if paired with a novel taste. Here, the effects of MFs on male and female rats were compared to determine whether there are sex differences in behavioral responses and whether these can be explained by ovarian steroid status. Rats were given 10-min access to a novel saccharin solution and then restrained within a 14-T magnet for 30 min. Locomotor activity after exposure was scored for circling and rearing. CTA extinction was measured with two-bottle preference tests. In experiment 1, males were compared with females across the estrous cycle after a single MF exposure. Females circled more and acquired a more persistent CTA than males; circling was highest on the day of estrus. In experiment 2, the effects of three MF exposures were compared among intact rats, ovariectomized females, and ovariectomized females with steroid replacement. Compared with intact rats, ovariectomy increased circling; estrogen replacement blocked the increase. Males acquired a stronger initial CTA but extinguished faster than intact or ovariectomized females. Thus the locomotor circling induced by MF exposure was increased in females and modulated by ovarian steroids across the estrous cycle and by hormone replacement. Furthermore, female rats acquired a more persistent CTA than male rats, which was not dependent on estrous phase or endogenous ovarian steroids.

Association of geomagnetic disturbances and suicides in Japan, 1999–2010

“…Previous reports have not found gender differences [7,9], but there is some evidence for such differences in the effects of various types of magnetic field [26][27][28][29][30][31]. Our results do not agree with some studies in which suicide numbers were found to be inversely related to geomagnetic activity [12,13].…”

Effects of Power-Frequency Magnetic Fields on Body Mass in Rats: A Pooled Analysis

“…In male rats, the relationship was a positive correlation, but in female rats the relationship was a negative correlation. This finding corresponds with evidence for sex differences in the effects of various types of magnetic field [12][13][14][15][16][17].…”

Lateral gradients significantly enhance static magnetic field‐induced inhibition of pain responses in mice—a double blind experimental study

“…Sexual steroids are also thought to play a role in the long term persistence of taste aversion: in ovariectomized rats taste aversion was found to be more prominent; however, estrogen replacement eliminated the aversive behavior. Male rats acquired a stronger initial aversion but extinguished faster than females [Cason et al, 2006]. Repeated exposure to SMF attenuates this biological response possibly due to habituation to vestibular perturbation subsequent to the exposure [Houpt et al, 2010].…”