Medical/biological study (experimental study)

Glucose administration attenuates spatial memory deficits induced by chronic low-power-density microwave exposure med./bio.

By: Lu Y, Xu S, He M, Chen C, Zhang L, Liu C, Chu F, Yu Z, Zhou Z, Zhong M

Published in: Physiol Behav 2012; 106 (5): 631-637

Aim of study (acc. to author)

To investigate whether glucose treatment attenuated memory deficity caused by chronic low-power microwave exposure and the effect of microwave exposure on hippocampal glucose uptake.

Background/further details

Three experiments were performed:
1.) The levels of blood glucose and insulin and hippocampal glucose uptake were examined in three groups: 1a) exposed, 1b) sham exposed and 1c) cage control.
2.) The Morris water maze was conducted with five groups: 2 a) exposed, 2 b) exposed plus glucose injection 30 minutes before the daily training session, 2 c) exposed plus saline injection 30 minutes before the daily training session, 2 d) sham exposed and 2 e) cage control.
3.) The radial arm maze task was also conducted with five groups: 3 a) exposed, 3 b) exposed plus glucose injection 30 minutes before the daily training session, 3 c) exposed plus saline injection 30 minutes before the daily training session, 3 d) sham exposed and 3 e) cage control (The radial arm maze is used to test spatial memory, a maze consisting of eight arms with food at the end of each arm and all radiating from a small circular central platform; counted is the number of reentries into an arm already visited).
Each group consisted of 6 adult male rats.

Endpoint

effects on the neurological system: hippocampal glucose uptake
cognitive/behavioral endpoints: spatial memory and learning

Exposure

- 2.45 GHz
- 2.45 GHz
- low level microwaves
- PW pulsed wave
- co-exposure

Exposure	Parameters
Exposure 1: 2.45 GHz Modulation type: pulsed Exposure duration: continuous for 3 h/day on 30 days	power density: 1 mW/cm² spatial average SAR: 0.2 W/kg average over time (whole body) SAR: 0.7 W/kg average over time (brain)

General information

Some groups of the rats were treated with 100 mg/ml glucose at a dose of 100 mg/kg 30 min before the daily training session.

Exposure 1

Main characteristics

Frequency	2.45 GHz
Type	electromagnetic field
Polarization	circular
Exposure duration	continuous for 3 h/day on 30 days

Modulation

Modulation type	pulsed
Pulse width	10 µs
Packets per second	800

Exposure setup

Exposure source	circular waveguide
Setup	circular waveguide constructed of galvanized wire screen in which a circulary polarized TE₁₁-mode field configuration was excited; 23.6 cm long cylindrical transparent plastic chamber with a diameter of 17.6 cm and a floor width of 14.5 cm was located in the middle of the wave guide; single rat placed inside the plastic chamber
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	1 mW/cm²	spatial average	-	-	-
SAR	0.2 W/kg	average over time	measured	whole body	-
SAR	0.7 W/kg	average over time	measured	brain	-

Reference articles

Li M et al. (2008): Elevation of plasma corticosterone levels and hippocampal glucocorticoid receptor translocation in rats: a potential mechanism for cognition impairment following chronic low-power-density microwave exposure
Chou CK et al. (1992): Long-term, low-level microwave irradiation of rats
McRee DI et al. (1984): Whole-body and local dosimetry in rats exposed to 2.45-GHz microwave radiation

Exposed system:

animal
rat/Wistar
whole body

Methods Endpoint/measurement parameters/methodology

endocrine changes: serum level of insulin (radioimmunoassay)
effects on the neurological system: hippocampal glucose uptake supplemented with or without insulin (staining with radiolabeled glucose, scintillation counter)
cognitive/behavioral endpoints: spatial memory and learning with or without glucose injection (Morris water maze, radial arm maze)
serum level of glucose (glucose oxidase method)

Investigated system:

blood samples, hippocampal slices
investigation on living organism

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The blood glucose and insulin levels were not affected by chronic microwave exposure, but the glucose uptake decreased in hippocampal slices of exposed rats compared to sham exposed rats. This effect was also observed in the presence of insulin.
Regarding the Morris water maze task, a significant prolongation in latency time occured during the training sessions and the time, spent in the target quadrant, was significantly reduced in the probe trail in exposed groups compared to sham exposed groups. The latency of the glucose-treated group was significantly reduced compared with the saline-treated group. In the probe trial, the glucose-treated rats spent a longer time in the target quadrant as compared with the saline treated group.
In the radial arm maze task, the errors in the exposed group were significantly increased compared to the sham exposed group. The errors in the glucose-treated group were significantly reduced compared with the saline-treated group.
The authors conclude that this study demonstrated that the hippocampus-dependent spatial learning and memory of rats could be impaired by chronic microwave exposure and that glucose administration attenuated these deficits.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

National Basic Research Program (Program 973), China
National Natural Science Foundation (NSFC), China

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