Advances in magnetic resonance imaging (MRI) are driving the development of MRI machines beyond conventional static magnetic field strengths to fields of 4-9 tesla (T). Little is known about the sensory or physiological effects of high strength static magnetic fields on mammals and humans. We have recently discovered that 30 min exposure to a 9.4 T field has behavioral and neural effects in rats. At the behavioral level, magnetic field exposure induced a conditioned taste aversion (CTA) after pairing with the taste of saccharin. CTA has proven to be a sensitive index of visceral perturbation or malaise induced by a treatment; therefore the magnetic field may be experienced by the rat as an aversive stimulus. At the neural level, the same exposure induced specific and significant c-Fos immunoreactivity in brainstem visceral relays (e.g. the nucleus of the solitary tract and parabrachial nucleus) and in vestibular nucluei (e.g., medial vestibular nucleus). Both the behavioral response and the pattern of c-Fos activation are similar to the effects of vestibular disturbances, such as rotation. We hypothesize that the magnetic field activates the rats' vestibular apparatus, causing vertigo; this would b consistent with reports of vertigo and nausea in humans exposed to 4 T fields. These findings suggest that CTA and c-Fos expression can be used in an animal model of the effects of high-strength, static magnetic fields. We propose to determine the sensitivity of rats using the large-bore, high-strength NMR magnets available at the National High Magnetic Field Laboratory. We will make lesions of sensory sites and nerves to determine the pathways for detection of the magnetic field. We will probe the underlying pharmacology with anti-emetics and other drugs that may attenuate the effects of the field. The acute behavioral effects will be measured by observational scoring; aversive or delayed effects will be measured by CTA expression; and the neural response will be quantified by c-Fos expression throughout the brain. These experiments will help predict the effects of future high-strength MRI on humans, and contribute to understanding the neural pathways underlying the effects.
| Houpt, Thomas A; Kwon, Bumsup; Houpt, Charles E et al. (2013) Orientation within a high magnetic field determines swimming direction and laterality of c-Fos induction in mice. Am J Physiol Regul Integr Comp Physiol 305:R793-803 |
| Houpt, Thomas A; Cassell, Jennifer; Carella, Lee et al. (2012) Head tilt in rats during exposure to a high magnetic field. Physiol Behav 105:388-93 |
| Houpt, Thomas A; Carella, Lee; Gonzalez, Dani et al. (2011) Behavioral effects on rats of motion within a high static magnetic field. Physiol Behav 102:338-46 |
| Houpt, Thomas A; Cassell, Jennifer A; Hood, Alison et al. (2010) Repeated exposure attenuates the behavioral response of rats to static high magnetic fields. Physiol Behav 99:500-8 |
| Cason, Angie M; Kwon, Bumsup; Smith, James C et al. (2010) c-Fos induction by a 14 T magnetic field in visceral and vestibular relays of the female rat brainstem is modulated by estradiol. Brain Res 1347:48-57 |
| Smith, Patrick L; Smith, James C; Houpt, Thomas A (2010) Interactions of temperature and taste in conditioned aversions. Physiol Behav 99:324-33 |
| Houpt, Thomas A; Houpt, Charles E (2010) Circular swimming in mice after exposure to a high magnetic field. Physiol Behav 100:284-90 |
| Cason, Angie M; Kwon, Bumsup; Smith, James C et al. (2009) Labyrinthectomy abolishes the behavioral and neural response of rats to a high-strength static magnetic field. Physiol Behav 97:36-43 |
| Houpt, Thomas A; Cassell, Jennifer A; Riccardi, Christina et al. (2007) Rats avoid high magnetic fields: dependence on an intact vestibular system. Physiol Behav 92:741-7 |
| Houpt, Thomas A; Cassell, Jennifer A; Cason, Angie M et al. (2007) Evidence for a cephalic site of action of high magnetic fields on the behavioral responses of rats. Physiol Behav 92:665-74 |
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