RESUMO
Effects of a static magnetic field (SMF) with strong gradient components were studied in black Swiss mice. Exposure to SMF (100-220 mT, 15-40 T/m for 1h) did not affect the threshold for detecting auditory brainstem responses. Serial seizures elevated the hearing threshold at some frequencies, but there was no difference between SMF-exposed and unexposed control mice. EEG changes were recorded during audiogenic seizures. Pretreatment with SMF prolonged seizure latency in response to stimulation with white noise of increasing intensity from 74 to 102 dBA (1 min interval between 2 and 4 dBA increments) without significant effects on seizure severity. Gender-related differences were not statistically significant. Stimulation with 10 min sound steps revealed prolongation of latency and reduction of seizure severity in SMF-exposed, but not unexposed, mice. Pretreatment with phenytoin (5 mg/kg) in combination with SMF had significantly greater effects on seizure latency and severity than either pretreatment alone. These findings indicate that the SMF studied here under different conditions elevated seizure threshold and had anticonvulsant properties in Black Swiss mice and increased the efficacy of a conventional anticonvulsant drug.
Assuntos
Campos Eletromagnéticos , Epilepsia Reflexa/fisiopatologia , Epilepsia Reflexa/terapia , Potenciais Evocados Auditivos do Tronco Encefálico/efeitos da radiação , Estimulação Acústica/métodos , Animais , Animais Recém-Nascidos , Anticonvulsivantes/uso terapêutico , Comportamento Animal/efeitos da radiação , Modelos Animais de Doenças , Relação Dose-Resposta à Radiação , Eletroencefalografia , Potenciais Evocados Auditivos do Tronco Encefálico/efeitos dos fármacos , Camundongos , Fenitoína/uso terapêutico , Psicoacústica , Tempo de Reação/efeitos dos fármacos , Tempo de Reação/efeitos da radiação , Índice de Gravidade de DoençaRESUMO
The effect on myosin phosphorylation from exposure to a magnetic field generated by an array of four permanent magnets was investigated. Two lateral positions in the non-uniform field over the array were explored, each at four vertical distances over the surface of the device. The rate of myosin phosphorylation was found to depend on the position laterally over the array as well as the distance from the device surface. The square magnet array was comprised of axially magnetized, cylindrical NdFeB permanent magnets arranged with poles of alternating polarity in a plane (MagnaBloc trade mark therapeutic device). Detailed dosimetry of the magnet array was compiled: the magnetic flux density averaged over the exposure volume spanned the range 0.7-86 mT for the eight different exposure positions. The corresponding range for the absolute field gradient was 0.4-20 T/m. Comparing the dosimetry to the experimental outcome, our results imply that magnetic field amplitude alone is not sufficient to describe the influence of the field in this preparation.