Analysis of age dependent effects of heat stress on EEG frequency components in rats / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To demonstrate changes in different frequencies of cerebral electrical activity or electroencephalogram (EEG) following exposure to high environmental heat in three different age groups of freely moving' rats.</p><p><b>METHODS</b>Rats were divided into three groups (i) acute heat stress--subjected to a single exposure for four hours at 38 degrees C; (ii) chronic heat stress--exposed for 21 days daily for one hour at 38 degrees C, and (iii) handling control groups. The digital polygraphic sleep-EEG recordings were performed just after the heat exposure from acute stressed rats and on 22nd day from chronic stressed rats by simultaneous recording of cortical EEG, EOG (electrooculogram), and EMG (electromyogram). Further, power spectrum analyses were performed to analyze the effects of heat stress.</p><p><b>RESULTS</b>The frequency analysis of EEG signals following exposure to high environmental heat revealed that in all three age groups of rats, changes in higher frequency components (beta 2) were significant in all sleep-wake states following both acute and chronic heat stress conditions. After exposure to acute heat, significant changes in EEG frequencies with respect to their control groups were observed, which were reversed partly or fully in four hours of EEG recording. On the other hand, due to repetitive chronic exposure to hot environment, adaptive and long-term changes in EEG frequency patterns were observed.</p><p><b>CONCLUSION</b>The present study has exhibited that the cortical EEG is sensitive to environmental heat and alterations in EEG frequencies in different sleep-wake states due to heat stress can be differentiated efficiently by EEG power spectrum analysis.</p>

Study of changes in some pathophysiological stress markers in different age groups of an animal model of acute and chronic heat stress

This study demonstrates the changes in six different pathophysiological parameters such as body weight, body temperature, fecal pellet count, blood-brain barrier [BBB] permeability, plasma corticosterone level and emergence of hemorrhagic peptic ulcer spots due to exposure to high environmental heat in three different age groups of freely moving rats. Each age group of rats was sub divided into three groups: [i] acute heat stress-subjected to a single exposure for four hours in the Biological Oxygen Demand incubator at 38°C; [ii] chronic heat stress-exposed for 21 days daily for one hour in the incubator at 38°C, and [iii] handling control groups. The data were recorded for the analyses of the changes in different parameters just after the heat exposure from acute stressed rats and on 1st, 3rd, 6th, 9th, 12th, 15th, 18th and 21st day on chronic stressed rats for body temperature, body weight, fecal pellets count. For the analysis of changes in three other parameters, BBB permeability, plasma corticosterone level and peptic ulcer spots following chronic exposure to high environmental heat, data were recorded on 22nd day for the analysis. Analysis of variance [ANOVA-1] of the observations demonstrates a significant increase in body temperature, fecal pellet count, BBB permeability [except in adult group], plasma corticosterone level and emergence of hemorrhagic peptic ulcer spots in all three different age group of rats due to exposure to acute heat stress. However, chronic heat was found responsible for the significant reduction in body weight in weaning and young rats, increase in body temperature, number of fecal pellets excreted [in early days of chronic stress] and number of peptic ulcer spots in all three age groups of rats. At the same time, BBB extravasations were not observed in rats except very mild in weaning group. The results of the present study indicate that the acute as well as chronic exposure to hot environment significantly alters the physiology of different organs of the body

Effect of acute and chronic heat exposure on frequency of EEG components in different sleep-wake state in young rats

The recent literatures indicate that central nervous system [CNS] is highly vulnerable to systemic hyperthermia induced by whole body heating on conscious animals. In the present study, cerebral electrical activity or EEG [electroencephalogram] following exposure to high environmental heat has been studied in moving rats. Rats were divided into three group [i] acute heat stress-subjected to a single exposure for four hours in the BOD [Biological Oxygen Demand] incubator at 38°C; [ii] chronic heat stress-exposed for 21 days daily for one hour in the incubator at 38°C, and [iii] handling control groups. EEG signals were recorded on paper along with in digital form on computer hard disk just after the heat exposure from acute stressed rats and on 22nd day from chronic stressed rats. EOG [electrooculogram] and EMG [electromyogram] were also recorded along with EEG to differentiate the different sleep-wake states. Following up, for each group of rats, power spectrum of the EEG for each sleep-wake states, and for all four hours of recording in two-second epochs were calculated and analyzed. The higher frequency components of the EEG power spectrum [beta 2] was found very sensitive to hot environment and changed significantly in all three sleep-wake states in comparison to the control rats following acute as well as chronic exposure to heat stress. This report demonstrates that the cortical EEG are sensitive to environmental heat and alterations in EEG frequencies in different state of mental consciousness due to high heat can be differentiated efficiently by EEG power spectrum analysis

assessment of changes in open-field and elevated plus-maze behavior following heat stress in rats

This paper presents the effect of high environmental heat on behavior of the male Charles Foster rats. Eighty rats were divided into three groups, subjected to [i] acute heat stress; [ii] chronic heat stress and [iii] handling control group. Animals were exposed to the hot environment in a biological oxygen demand incubator at 38 +/- 1°C [relative humidity 45-50%] for four hours of continuous single exposure for acute heat stress and one hour daily for 21 days for chronic stress. The assessment of behavior was performed just after the stress for acute stress group and for chronic stress group, on 1st, 7th, 14th and 21st day of stress in open-field [OF] and Elevated plus-maze [EPM] apparatus. Following acute heat exposure, a significant increase in immobilization with decrease in rearing, grooming, and ambulation behavior was seen in OF. While in EPM, a highly significant increase in transfer latency with decrease in percentage time on open arms and number of arms crossed were recorded. During chronic heat stress, in OF, decrease in immobilization [1st, 7th and 14th day] and ambulation [1st and 7th day] was observed with significant increase in rearing [1st day] and grooming behavior [1st and 7th day]. On the other hand, in EPM, significant decreases in number of arms crossed [1st, 7th and 14th day] and transfer latency [1st day] were recorded with increase in percentage time on open arms [1st and 7th day]. However, no behavioral changes were observed on 21st day that show the adaptations of animals to the chronic exposure to the hot environmental conditions

Effect of p-CPA pretreatment on EEG power spectra in experimental open brain injury in rats

Continuous four hours EEG [electroencephalogram] recordings and its power spectrum analysis using fast fourier transform [FFT] in urethane anesthetized male Charles Foster rats were performed in two groups: open brain injury and p-CPA [para-Chlorophenylalanine] pretreated before brain injury, respectively, and compared with the EEG power spectrum of control rats. The EEG power spectrum analysis showed that there was a faster recovery in p-CPA pretreated group than the injury group of rats. The results showed that the p-CPA [a 5-HT inhibitor] prevents pathological changes following brain injury. Simultaneously, the inference can also be drawn that EEG power spectrum analysis is a useful technique for monitoring the brain injury and its recovery following pharmacological treatments