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Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1–80 Hz
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 272–276 (2004) 2424–2425
Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1–80 Hz ! a,b, Mar!ıa J. Azanzaa,*, Ana C. Calvoa, A. del Moralc R.N. Pe! rez Bruzon a
Laboratorio de Magnetobiolog!ıa, Facultad de Medicina, Dept. Anatom!ıa e Histolog!ıa Humanas, Universidad de Zaragoza, Zaragoza 50009, Spain b Centro Nacional de Electromagnetismo Aplicado, Universidad de Oriente, Santiago de Cuba, Cuba c Laboratorio de Magnetismo, DFMC-ICMA, Universidad de Zaragoza & CSIC, Zaragoza 50009, Spain
Abstract Intracellular recordings from single unit molluscan neurones under exposure to ELF-MF (1 mT, 0.1–80 Hz), show that neurone frequency activity, f ; decreases with the applied magnetic field frequency, fM ; a phenomenon which indicates a frequency-window effect for the neurone membrane response. The HMHW of the window amounts between 2–10 Hz. An explanation of this phenomenon is proposed. r 2003 Elsevier B.V. All rights reserved. PACS: 87.40 Keywords: ELF-MF neurone effects; Diamagnetic anisotropy; Neuron frequency responses
We have observed elsewhere that molluscan neurones show a higher sensitivity to extremely low-frequency applied magnetic fields (ELF-MF) of 50 Hz [1] than to applied static magnetic fields (SMF) [2]. We here report the responses of neurones under exposure to ELF-MF of low fixed intensity (B0 ¼ 1 mT) and frequencies in the range of human electroencephalography (EEG) range: slow waves (o1 Hz: 0.3–0.8 Hz); delta waves (1–4 Hz); spindle waves (7–14 Hz); theta waves (5–7 Hz); alpha waves (8–12 Hz); mu waves (12–18 Hz); beta waves (15– 30 Hz) and gamma waves (30–80 Hz). There exists the possibility that incident ELF-MF, from appliances producing frequencies near to the typical ones of the human EEG, could interact with neurones bioelectric activity, thereby inducing a kind of resonant effect, modifying in turn the brain activity since neurones in a network communicate each other through a frequency code. The experiments were performed on single unit neurones randomly selected from Helix aspersa brain *Corresponding author. Tel.: + 34-976-761673; fax: + 34976-761754. E-mail address: [email protected] (M.J. Azanza).
ganglia in Ringer solution. Intracellular recordings were made using glass micro-electrodes filled with 1 M potassium acetate (pH 6.8) (tip resistance 2–20 MO). The brain ganglia (about 4 mm2 surface) were placed in the centre of a pair of Helmholtz coils (11 cm diameter separated 5.5 cm), producing a homogeneous ELF-MF. The recordings were made in real time. No temperature variation in the Ringer solution was observed during MF exposure. Sinusoidal ELF-MF of weak amplitude B0 ¼ 1 mT and frequency, fM ; from 0.1 to 80 Hz were applied. We have made 14 experiments on randomly selected neurones (V3, V4, V7, V9, V14, D1, D4, F1, F16 and F26) [3]. The experiments were repeated 5 times on the neurone F1 in order to check out the reproducibility response. The applied frequency was increased progressively, each one being maintained during 1 min. Specific responses have been observed: spikes amplitude increase, recruitment induced activity and, central to this work, a frequency decrease (in 10 out of the 14 experiments made) (Fig. 1). Neurone responses indicate a ‘‘frequency window’’ (f.w.) effect. Each neuron shows intrinsic properties which determine its firing frequency with a value defined as characteristic spontaneous firing,
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.846
ARTICLE IN PRESS ! et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 2424–2425 R.N. P!erez Bruzon
Fig. 1. Modification of neurone D1 (left parietal Helix aspersa ganglion [3]) activity under applied ELF-MF of 1 mT and frequencies fM =0.1–80 Hz, each one applied for 1 min. Recording (a) spontaneous activity (f0 ¼ 3:8 spikes/s). Recordings (b) and (c) recruitment induced activity under exposure to fM of 10 and 15 Hz. Recording (d) spikes frequency decreases is enhanced with increasing fM of 20 and 30 Hz.
f0 ; which changes in a range of 0.1–4.0 spikes/s among the different Helix aspersa neurones. We have observed that when the frequency fM increases, the firing neurone frequency, f ; strongly decreases as shown in Fig. 1. A similar effect was early observed by Bawin et al. [4] in in vitro chicken brain around a central frequency of 16 Hz, with windows of HMHWD8 and 20 Hz, so called ‘‘frequency window’’ for the response of brain to weak ELF-MF. Our observation also indicates an f.w. phenomenon, but within a single unit neurone. In a brain f.w. is a consequence of a kind of resonance, the width being likely determined by the statistical distribution of brain neurons firing frequencies. Here we observe that a statistical distribution of firing frequencies seems also exits for a single neurone. In Fig. 2 is shown that the neurone firing frequency, f ; rapidly decreases with increasing fM ; with a HMHW of GE10 Hz.This suggests a kind of ‘‘resonance’’ effect, likely due to a statistical distribution of firing frequencies for the Ca2+-operated-K+-protein channels. As we have shown before [5] the membrane forms phospholipids (PP) clusters of average size Npp=5 106 for a neurone of D100 mm diameter, which act cooperatively due to superdiamagnetism. This phenomenon is due to the strong diamagnetic susceptibility of the PP molecules, with a measured difference Dw ¼ wjj w> ¼ ð2:870:10Þx106 (SI units), between the long and short axis of the rod-like PP molecule. When the cluster PP oscillate together (as NN) under the AC torque exerted by the MF, on approaching their ends, nearest neighbours PP-bounded Ca2+ ions are liberated at both sides of the membrane through an overall Coulomb explosion process at both membrane sides. Ca2+ ions
2425
Fig. 2. The variation of the F1 (right parietal ganglion [3]) neurone frequency, f ; has been plotted versus the AC applied MF of 1 mT amplitude for frequencies fM =2–80 Hz, each one applied for 1 min. Average f0 (E2.4 spikes/s) was measured from 5 min spontaneous neurone activity recording. The f.w. HMHW is GD10 Hz.
free liberated in the cytosol activates the Ca2+-operatedK+-channels, and the sorting of K+ ions hyperpolarizes the membrane potential. Protein channels also form correlated clusters [5]. Therefore our explanation of the observed ‘‘resonance’’ is that when fM coincides with some protein cluster f0 ; Ca2+-operated-K+- channels are in phase with the AC field, the effect being reinforced. The HMHW G therefore would measure the statistical distribution of f0 within the different populations of protein channels. The f decrease is likely due to the decreasing sizes of protein channel population with increasing f0 : Therefore what the ACMF does is to explore (sampling) the protein channels populations. The average size of protein clusters was determined by studying the Brms variation of f ; which follows a model 2 dependence f ðBÞ ¼ f0 eaBrms ; with model parameter a proportional to Npp (and to Dw) [5]. Further experiments and theoretical work is in progress. We acknowledge the Spanish Ministry of Science and Technology for Projects and grants PROFIT PROJECT: FIT-07000-2001-346. FIT-2002-070000-2002623.
References [1] M.J. Azanza, A. del Moral, J. Magn. Magn. Mater. 177–181 (1998) 1451. [2] M.J. Azanza, A. del Moral, J. Magn. Magn. Mater. 140–144 (1995) 1464. [3] G.A. Kerkut, J.D.C. Lambert, R.J. Gayton, J.E. Locker, R.J. Walker, Comput. Biochem. Physiol. 50A (1975) 1. [4] S.M. Bawin, A. Sheppard, W.R. Adey, Bioelectrochem. Bioenergetics 5 (1978) 67. [5] M.J. Azanza, A. del Moral, Prog. Neurobiol. 44 (1994) 517.
Journal of Magnetism and Magnetic Materials 272–276 (2004) 2424–2425
Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1–80 Hz ! a,b, Mar!ıa J. Azanzaa,*, Ana C. Calvoa, A. del Moralc R.N. Pe! rez Bruzon a
Laboratorio de Magnetobiolog!ıa, Facultad de Medicina, Dept. Anatom!ıa e Histolog!ıa Humanas, Universidad de Zaragoza, Zaragoza 50009, Spain b Centro Nacional de Electromagnetismo Aplicado, Universidad de Oriente, Santiago de Cuba, Cuba c Laboratorio de Magnetismo, DFMC-ICMA, Universidad de Zaragoza & CSIC, Zaragoza 50009, Spain
Abstract Intracellular recordings from single unit molluscan neurones under exposure to ELF-MF (1 mT, 0.1–80 Hz), show that neurone frequency activity, f ; decreases with the applied magnetic field frequency, fM ; a phenomenon which indicates a frequency-window effect for the neurone membrane response. The HMHW of the window amounts between 2–10 Hz. An explanation of this phenomenon is proposed. r 2003 Elsevier B.V. All rights reserved. PACS: 87.40 Keywords: ELF-MF neurone effects; Diamagnetic anisotropy; Neuron frequency responses
We have observed elsewhere that molluscan neurones show a higher sensitivity to extremely low-frequency applied magnetic fields (ELF-MF) of 50 Hz [1] than to applied static magnetic fields (SMF) [2]. We here report the responses of neurones under exposure to ELF-MF of low fixed intensity (B0 ¼ 1 mT) and frequencies in the range of human electroencephalography (EEG) range: slow waves (o1 Hz: 0.3–0.8 Hz); delta waves (1–4 Hz); spindle waves (7–14 Hz); theta waves (5–7 Hz); alpha waves (8–12 Hz); mu waves (12–18 Hz); beta waves (15– 30 Hz) and gamma waves (30–80 Hz). There exists the possibility that incident ELF-MF, from appliances producing frequencies near to the typical ones of the human EEG, could interact with neurones bioelectric activity, thereby inducing a kind of resonant effect, modifying in turn the brain activity since neurones in a network communicate each other through a frequency code. The experiments were performed on single unit neurones randomly selected from Helix aspersa brain *Corresponding author. Tel.: + 34-976-761673; fax: + 34976-761754. E-mail address: [email protected] (M.J. Azanza).
ganglia in Ringer solution. Intracellular recordings were made using glass micro-electrodes filled with 1 M potassium acetate (pH 6.8) (tip resistance 2–20 MO). The brain ganglia (about 4 mm2 surface) were placed in the centre of a pair of Helmholtz coils (11 cm diameter separated 5.5 cm), producing a homogeneous ELF-MF. The recordings were made in real time. No temperature variation in the Ringer solution was observed during MF exposure. Sinusoidal ELF-MF of weak amplitude B0 ¼ 1 mT and frequency, fM ; from 0.1 to 80 Hz were applied. We have made 14 experiments on randomly selected neurones (V3, V4, V7, V9, V14, D1, D4, F1, F16 and F26) [3]. The experiments were repeated 5 times on the neurone F1 in order to check out the reproducibility response. The applied frequency was increased progressively, each one being maintained during 1 min. Specific responses have been observed: spikes amplitude increase, recruitment induced activity and, central to this work, a frequency decrease (in 10 out of the 14 experiments made) (Fig. 1). Neurone responses indicate a ‘‘frequency window’’ (f.w.) effect. Each neuron shows intrinsic properties which determine its firing frequency with a value defined as characteristic spontaneous firing,
0304-8853/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.846
ARTICLE IN PRESS ! et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 2424–2425 R.N. P!erez Bruzon
Fig. 1. Modification of neurone D1 (left parietal Helix aspersa ganglion [3]) activity under applied ELF-MF of 1 mT and frequencies fM =0.1–80 Hz, each one applied for 1 min. Recording (a) spontaneous activity (f0 ¼ 3:8 spikes/s). Recordings (b) and (c) recruitment induced activity under exposure to fM of 10 and 15 Hz. Recording (d) spikes frequency decreases is enhanced with increasing fM of 20 and 30 Hz.
f0 ; which changes in a range of 0.1–4.0 spikes/s among the different Helix aspersa neurones. We have observed that when the frequency fM increases, the firing neurone frequency, f ; strongly decreases as shown in Fig. 1. A similar effect was early observed by Bawin et al. [4] in in vitro chicken brain around a central frequency of 16 Hz, with windows of HMHWD8 and 20 Hz, so called ‘‘frequency window’’ for the response of brain to weak ELF-MF. Our observation also indicates an f.w. phenomenon, but within a single unit neurone. In a brain f.w. is a consequence of a kind of resonance, the width being likely determined by the statistical distribution of brain neurons firing frequencies. Here we observe that a statistical distribution of firing frequencies seems also exits for a single neurone. In Fig. 2 is shown that the neurone firing frequency, f ; rapidly decreases with increasing fM ; with a HMHW of GE10 Hz.This suggests a kind of ‘‘resonance’’ effect, likely due to a statistical distribution of firing frequencies for the Ca2+-operated-K+-protein channels. As we have shown before [5] the membrane forms phospholipids (PP) clusters of average size Npp=5 106 for a neurone of D100 mm diameter, which act cooperatively due to superdiamagnetism. This phenomenon is due to the strong diamagnetic susceptibility of the PP molecules, with a measured difference Dw ¼ wjj w> ¼ ð2:870:10Þx106 (SI units), between the long and short axis of the rod-like PP molecule. When the cluster PP oscillate together (as NN) under the AC torque exerted by the MF, on approaching their ends, nearest neighbours PP-bounded Ca2+ ions are liberated at both sides of the membrane through an overall Coulomb explosion process at both membrane sides. Ca2+ ions
2425
Fig. 2. The variation of the F1 (right parietal ganglion [3]) neurone frequency, f ; has been plotted versus the AC applied MF of 1 mT amplitude for frequencies fM =2–80 Hz, each one applied for 1 min. Average f0 (E2.4 spikes/s) was measured from 5 min spontaneous neurone activity recording. The f.w. HMHW is GD10 Hz.
free liberated in the cytosol activates the Ca2+-operatedK+-channels, and the sorting of K+ ions hyperpolarizes the membrane potential. Protein channels also form correlated clusters [5]. Therefore our explanation of the observed ‘‘resonance’’ is that when fM coincides with some protein cluster f0 ; Ca2+-operated-K+- channels are in phase with the AC field, the effect being reinforced. The HMHW G therefore would measure the statistical distribution of f0 within the different populations of protein channels. The f decrease is likely due to the decreasing sizes of protein channel population with increasing f0 : Therefore what the ACMF does is to explore (sampling) the protein channels populations. The average size of protein clusters was determined by studying the Brms variation of f ; which follows a model 2 dependence f ðBÞ ¼ f0 eaBrms ; with model parameter a proportional to Npp (and to Dw) [5]. Further experiments and theoretical work is in progress. We acknowledge the Spanish Ministry of Science and Technology for Projects and grants PROFIT PROJECT: FIT-07000-2001-346. FIT-2002-070000-2002623.
References [1] M.J. Azanza, A. del Moral, J. Magn. Magn. Mater. 177–181 (1998) 1451. [2] M.J. Azanza, A. del Moral, J. Magn. Magn. Mater. 140–144 (1995) 1464. [3] G.A. Kerkut, J.D.C. Lambert, R.J. Gayton, J.E. Locker, R.J. Walker, Comput. Biochem. Physiol. 50A (1975) 1. [4] S.M. Bawin, A. Sheppard, W.R. Adey, Bioelectrochem. Bioenergetics 5 (1978) 67. [5] M.J. Azanza, A. del Moral, Prog. Neurobiol. 44 (1994) 517.