Effects of high power microwave pulses on synaptic transmission and long term potentiation in hippocampus

Abstract

Effects of short, extremely high power microwave pulses (EHPP) on neuronal network function were explored by electrophysiological techniques in the isolated rat hippocampal slice model. Population spikes (PS) in the CA1 area were evoked by repeated stimulation (1 per 30 s) of the Schaffer collateral pathway. A brief tetanus (2 s at 50 Hz) was used to induce long term potentiation (LTP) of synaptic transmission. In three different series of experiments with a total of 160 brain slices, the EHPP irradiation was performed before, during, or after the tetanus. The EHPP carrier frequency was 9.3 GHz, the pulse width and repetition rate were from 0.5 to 2 micros and from 0.5 to 10 Hz, respectively, and the peak specific absorption rate (SAR) in brain slices reached up to 500 MW/kg. Microwave heating of the preparation ranged from 0.5 degrees C (at 0.3 kW/kg time average SAR) to 6 degrees C (at 3.6 kW/kg). The experiments established that the only effect caused by EHPP exposure within the studied range of parameters was a transient and fully reversible decrease in the PS amplitude. Recovery took no more than a few minutes after the cessation of exposure and return to the initial temperature. This effect's features were characteristic of an ordinary thermal response: it was proportional to the temperature rise but not to any specific parameter of EHPP, and it could also be induced by a continuous wave (CW) irradiation or conventional heating. Irradiation did not affect the ability of neurons to develop LTP in response to tetanus or to retain the potentiated state that was induced before irradiation. No lasting or delayed effects of EHPP were observed. The results are consistent with the thermal mechanism of EHPP action and thus far provided no indication of EHPP-specific effects on neuronal function.

Services to Operate and Maintain a Microwave Research Laboratory

“…6. Pakhomov, A.G;and Murphy, M.R. [2001]: Retaining of the long-term potentiation in hipocampal slices after high peak power microwave exposure and heating.…”

“…7. Pakhomov, A.G;and Murphy, M.R. [2001]: Effects of extremely high power microwave pulses on the population spike and long-term potentiation in rat hippocampal slices.…”

“…Should gaps in knowledge be considered? *** Personal communication, M. R. Murphy, 2001. April 2002 There are some questions regarding the most appropriate model for developing standards and accurate methods for determining compliance.…”

Inaccurate official assessment of radiofrequency safety by the Advisory Group on Non-ionising Radiation

“…This heating study had reported an effect, an in vitro recoverable decrease in population spike amplitude in the hippocampus in response to the RF signal, but no effect on long-term potentiation (50 (2)]. An effect on cells is not unlikely when there were significant effects in all of the relevant studies on membranes (excluding BBB), all of the studies except one on direct protein effects, the majority of the studies on oxidative stress or male fertility, all of the included in vitro genotoxicity studies on epithelial cells [see c; page 84 (2)] and 47% of in vitro genotoxicity studies which could have been included in the report (see c; SI).…”

Real Time Radio Frequency Exposure for Bio-Physical Data Acquisition

“…The most used experimental samples are excitable cells and tissues since they are likely to be sensitive to EM stimulation and to display reversible effects. They include single neuronal cells Platano et al, 2006;Marchionni et el., 2005;Paffi et al, 2007), neuronal networks (Tattersall et al, 2001;Pakhomov et al, 2003;Koester et al, 2007;Merla et al, 2011), inner ear hair cells of the organ of Corti (El Ouardi et al, 2011), and muscles, both skeletal (Lambrecht et al, 2006) and cardiac (Pakhomov et al, 2000). The observables are mostly electrophysiological parameters, such as the ionic current and the membrane voltage at the level of single cell, or the field potential generated by a group of interconnected neuronal cells.…”