Theophylline can improve microwave-induced memory impairment in mice

Theophylline can improve microwave-induced memory impairment in mice

【Abstract】 Objective To study the effect of theophylline on memory impairment induced by microwave in mice.

Method 1 The mice were grouped with microwave radiation doses of 0, 5, 10, 25, 50 mW/cm2 and irradiated for 20 min respectively. The anus temperature before and after radiation was recorded. The passive avoidance avoidance test was used to record the number of times the mice completed training and the latency after 24 hours as an indicator to evaluate their learning and memory. 2 Intravenous injection of normal saline or theophylline 30 min before pseudo-microwave irradiation or 50 mW/cm2 microwave irradiation, and then test the learning and memory ability of the mice.

Results 1 Compared with the control group, mice exposed to microwave irradiation at 50 mW/cm2 caused memory and memory retention in animals, and also caused an increase in body temperature in mice (P < 0101 or P < 0105). The learning and memory ability of the mice in the 2ophylline + 50 mW/cm2 microwave irradiation group was significantly better than that in the normal saline + 50 mW/cm2 group (P < 0101).

Conclusion The experimental results suggest that: 1 Microwave thermal effect is the main cause of cognitive impairment. 2 Theophylline can improve microwave-induced memory impairment in mice, suggesting that endogenous adenosine mediates the effects of microwave damage.

【Key words】 Theophylline; Microwave; Avoiding darkness experiment; Memory disorder

Microwave radiation can impair the cognitive capabilities of humans and animals. Acute or long-term animal experiments have shown that microwaves can destroy the high-level activities of animals such as learning and memory [1]. It is generally believed that the heat generated by microwave radiation is a major factor in the microwave effect [2]. When the brain tissue absorbs microwave energy, the local tissue accelerates the metabolic activity of the brain tissue and interferes with the normal energy metabolism of the brain tissue [3]. Adenosine, a metabolite of adenosine t rap hosp hate (A TP), is an important stress messenger and homeostatic regulator. A variety of pathological factors such as ischemia, high temperature, hypoxia, electrical stimulation, etc. can stimulate the release of adenosine in the brain. These factors can lead to increased energy requirements or lack of energy metabolism substrates [4], resulting in insufficient tissue energy supply. From the perspective of microwave thermal effects, we speculate that microwave radiation may also activate the adenosine metabolic pathway in the body and cause dysfunction of the body. To this end, this experiment is to first study the learning and memory impairment induced by microwave in mice by avoiding darkness experiment, and to study the effect of non-specific antagonist of adenosine receptor (theophylline) on microwave radiation to evaluate adenosine metabolism in vivo. The possible role of pathways in animal memory impairment caused by microwaves.

Materials and Methods

I. Animals and reagents

Male Kunming mice weighing 20-24 g, a total of 120 mice. Theophylline (t heop hylline) is configured to the desired concentration with physiological saline before use.

Second, the method

11 Microwave source and radiation mode: Pulsed microwave source with a frequency of 2860 MHz. The mice were placed in an organic radiation box during irradiation, and the upper square horn loudspeaker radiated throughout the body. The average power density of the microwave radiation is continuously adjustable in the range of 5 mW/cm 2 to 100 mW/cm 2 . The mice in the pseudoradiation group were treated the same, but the microwave source was not activated.

21 Passive avoidance avoidance test in mice: The detection equipment is two communicating chambers and darkrooms (20 cm×10 cm×10 cm), the bright room is illuminated by a 7 W bulb, and the bottom of the dark chamber is an iron fence structure. The current can be applied to the incoming animal by electric shock. The mice were placed in the bright room during training. When the mice entered the dark room, they were stimulated by electric current. Immediately after the electrical stimulation, the mice were taken out and returned to the bright room for the next experiment until the mice stayed in the bright room for more than 60 s, and the number of times the mice completed the training was recorded. After 24 h, the memory retention test was performed, and the mice were again placed in the bright room, and the incubation period required for all the mice to enter the dark room was recorded, and the incubation period was set at 300 s. 31 Grouping and experimental treatment: The mice were randomly divided into 11 groups, 10 in each group, grouped as follows: 1 Microwave radiation group: Animals were divided into 0, 5, 10, 25 and 50 mW/cm2 according to the microwave radiation dose size. . The duration of the radiation was 20 min [5], and an electronic thermometer was used to record the anal temperature before and after the radiation of the animal. The 0mW/cm2 group was the sham exposure group and served as a control group. The behavioral experiment was started immediately after the end of the radiation. 2 Theophylline intervention group: the radiation method was the same as before, the radiation dose was 50mW/cm2, and theophylline was injected intraperitoneally 30 minutes before the radiation. Animals were divided into 6 groups, namely “Fake Microwave Radiation + Saline Group”, “Fake Microwave Radiation + 1215 mg/kg Theophylline Group”, “Fake Microwave Radiation + 25 mg/kg Theophylline Group”, “Microwave Radiation + Physiology” "Brine group", "microwave radiation + 1215 mg / kg theophylline group", "microwave radiation + 25 mg / kg theophylline group".

Third, statistical processing

The experimental data is expressed in the form of Š x ± s. Using SPSS statistical software, Kruskal2Wallis nonparametric one-way ANOVA was used to test the significance of different groups of data. P < 0105 showed significant differences, and P < 0101 showed very significant differences.

result

First, the effect of microwave on the memory ability of mice

During the darkness test, the mice were given an electric shock every time they entered the darkroom. The faster the mouse establishes a connection between the situation and the fear, the less the number of shocks received, reflecting the greater the ability to acquire memory. Microwave radiation before training can lead to a decrease in memory acquisition ability in mice to avoid darkness (Table 1), and the behavior of mice after 5 mW/cm2, 10 mW/cm2 microwave irradiation compared with the number of required training in the pseudo-microwave radiation group. No significant change (P > 0105). Although the number of completed training in the 25 mW/cm2 group was higher than that in the sham group, there was no statistical difference. After microwave irradiation at 50 mW/cm2, the number of times the mice completed training was significantly increased compared with the pseudo-microwave radiation group (P < 0101). After the mouse darkening experiment was completed, the incubation period from the bright room to the dark room was tested the next day. The longer the incubation period, the stronger its memory retention. Kruskal2Wallis one-way analysis of variance analysis found that microwave radiation could impair the memory retention of mice in a dependent manner (Table 1). Compared with the pseudo-microwave radiation group, the latency of the mice decreased to some extent from the radiation dose of 25 mW/cm2, but the statistical difference was not significant, while the 50 mW/cm2 microwave radiation was significantly reduced. The latency of memory retention in mice (P < 0101). The experiment used repeated training methods. Although the number of times the animals completed the training after microwave irradiation was different, they all reached the same standard. They did not enter the dark room within 60 s. Therefore, the length of the incubation period can reflect the difference in animal memory consolidation ability. The experimental results show that higher doses of microwave radiation have a destructive effect on both animal memory acquisition and consolidation.

After the end of the irradiation, the temperature of the anus of the mouse was measured using an electronic thermometer. The anal temperature of the mice in the 50 mW/cm2 group increased significantly, but increased slightly in the 25 mW/cm2 group, while the temperature in the control, 5mW/cm2, and 10 mW/cm2 groups did not change (Table 2), indicating high dose of microwave radiation. Not only damages animal memory, but also causes the body temperature to rise.

2. Effect of theophylline on memory impairment induced by microwave in mice

Theophylline is a non-specific antagonist of adenosine receptors A1 and A2. The doses of theophylline used in this experiment were 1215 mg/kg and 25 mg/kg, respectively [6]. At 30 min after animal administration, the microwave was irradiated at an average power density of 50 mW/cm2, and then subjected to darkness test training. Compared with the number of trainings in the "fake microwave radiation + saline group" mice, there was no change in the behavior of the "sham microwave radiation + theophylline group", but the number of training required by the mice in the microwave irradiation group was significantly increased (P < 0101). ). The number of trainings in the "microwave radiation + theophylline group" mice did not change significantly compared with the sham radiation group, and was significantly reduced compared with the "microwave radiation group + saline group" (P < 0101) (Table 3), suggesting that After theophylline, microwave radiation no longer impairs the acquired training of mice, that is, theophylline can block the damage effect of microwave on memory acquisition.

In terms of memory retention, it can be seen from the memory retention test results of the next day in mice (Table 3) that the latency of the "microwave radiation + saline group" was significantly lower than that of the "fake microwave radiation + saline group" (P < 0101), the latency of "microwave radiation +25 mg / kg theophylline group" was significantly higher than that of "microwave radiation + saline group", although there was no statistical difference between the two, but "microwave radiation + 25 mg The latency of the /kg theophylline group was not significantly different from that of the “fake microwave radiation + 25 mg/kg theophylline group”, and even the difference was not significant compared with the “fake microwave radiation + saline group”, suggesting that theophylline It can alleviate the memory retention disorder caused by microwave.

discuss

First, microwave damage to animal cognition

Due to the special sensitivity of the nervous system, microwave damage to the brain's advanced activities has attracted widespread attention from the public and researchers. In this experiment, it was found that after high-dose microwave irradiation, the memory of the mice was impaired, and the core temperature rose above 2 °C. The low-dose microwaves that did not significantly change the body temperature of the animals did not significantly affect the learning and memory ability of the animals. The results of this experiment are similar to those of Mickley et al. [5]. Supporting the microwave thermal effect is the main cause of cognitive impairment in animals. When the energy of microwave radiation absorbed by the animal exceeds its own thermoregulatory capacity, it can produce harmful tissue heating reactions. Lead to changes in animal behavior [7]. It is worth mentioning that in recent years, some studies have suggested that under very low doses of microwave radiation, some of the animal's complex behaviors, such as discrimination and perception, have changed, emphasizing the "non-thermal effect" of microwave damage [8]. However, these experiments lack sufficient persuasive power because they are difficult to obtain good repeated verification. The White Paper published by the Institute of Electrical and Electronics Engineers also believes that tissue heating caused by radiation after absorption of microwave energy in the brain can almost explain the results of studies on animal behavior changes caused by known microwaves [9].

Second, the role of adenosine in the microwave effect

After the brain absorbs the energy of the microwave, local heating can accelerate the metabolism of the neurons. In the case of a certain energy supply, the ATP consumption can be increased, and the neurons are in a relative state of deficiency [10]. Under the action of adenylate kinase and 5'2 nucleotidase, a slight change in A TP can cause a large change in the concentration of extracellular adenosine 2 adenosine [11]. As a general metabolic stress messenger, adenosine secretion capacity is usually greatly enhanced when tissue energy supply is insufficient. Tissue heating caused by microwave radiation may also stimulate the massive release of adenosine to reduce the metabolic activity of the brain, thereby balancing the energy supply and demand relationship. Excessive release of adenosine activates adenosine receptors A1, A2 (A2A and A2B) and A3, and regulates cognitive activities such as brain learning and memory. Therefore, adenosine may be involved in the cognitive impairment effect caused by microwave. In order to verify the hypothesis, this study used low-dose theophylline before the microwave irradiation of the animals, and found that compared with the radiation group, the memory of the "microwave radiation + theophylline group" mice showed a significant improvement in memory, indicating that theophylline can block Broken microwave damage to memory. Although there was no significant difference in the incubation period between the "microwave radiation + 25 mg/kg theophylline group" animals and the "microwave radiation + saline group" animals, 25 mg/kg theophylline could greatly improve the animal memory after microwave irradiation. There was no statistical difference between the results and the pseudo-microwave radiation group. Consistent with the existing study [6], the theophylline dose used in this experiment had no effect on the acquisition and maintenance of mouse darkening experiments. It is currently believed that the most important effect of low-dose theophylline is to block adenosine receptors [12], so these results suggest that microwave radiation may activate the adenosine metabolism system, while adenosine may regulate neuronal activity through adenosine receptors. Thereby affecting the learning and memory activities of animals. Adenosine usually has two relatively important pathways for the regulation of learning and memory activities: one is an indirect pathway that inhibits the activity of the midbrain and forebrain cholinergic neurons through the A1 receptor [13], regulating the awake state of the animal. Maintaining animal attention, while vigilance and awakening are critical to the completion of animal cognitive tasks. The other is a direct pathway, adenosine can regulate the synaptic plasticity of hippocampus and other regions [14], while the latter is considered to be the material basis of learning and memory. Because memory requires the maintenance of animal attention and moderate alertness, and the consolidation of memory depends on the plasticity of hippocampus and other regions [15,16], adenosine may be involved in the microwave by modulating the activity of neurons in different regions of the brain. Animals learn memory disorders. It is worth emphasizing that we found that theophylline did not completely block the damage of microwave to memory consolidation, suggesting that the adenosine metabolic pathway may be one of the microwave pathways. Because the microwave effect and the learning and memory mechanism are very complicated, depending on the microwave frequency, radiation intensity and radiation method, the brain area and cognitive activities will change greatly. Therefore, the process of adenosine participation needs further research. .