To analyze the causes of changes in SCP during stress, we studied the relationship between the level of the stress hormone cortisol and brain SCP parameters in 19 healthy subjects of both sexes (15 women, 4 men) of advanced age (63.5 + 4.1 years). All subjects to exclude cerebral pathology underwent neurological and EEG examination.
SCP was recorded in the morning. Immediately before a neurophysiological examination, blood was taken on an empty stomach on the same day for subsequent determination of cortisol. It was produced in blood serum by the radioimmunological method in the laboratory of clinical biochemistry SC SC RAMS.
The serum cortisol content averaged 451.1 + 55.3 nmol / L and did not differ significantly between men and women. No correlation between cortisol content and autonomic indicators (pulse rate, blood pressure, and Kerdo index) was observed.
Using one-way analysis of variance (ANOVA), differences in SCP parameters were evaluated in subjects with a low, medium, and high cortisol content. As a criterion for dividing into groups, the values of the lower and upper quartiles of the distribution of cortisol values were used. In subjects with a high level of cortisol, as a rule, there were traumatic situations: divorce, death of close relatives.
With an increase in the cortisol content, the SCP value significantly increased in the frontal, occipital, and right temporal regions, and the averaged over the entire leads of the SCP was also increased .
On the ordinate axis – SCP values, mV, on the abscissa axis – SCP assignments
The obtained data confirmed the idea that the activation of GNSS with an increase in cortisol is accompanied by an increase in SCP, which is obviously a consequence of the restructuring of cerebral energy metabolism, leading to increased glycolysis and the development of lactic acidosis in the brain.
Acidification of the brain enhances oxidative stress, adversely affecting brain activity, especially in old age. With aging, an increase in cortisol and brain SCP is associated with an increase in the latencies of the late components of evoked potentials, indicating a slowdown in information processes in the polysynaptic and afferent systems of the brain .
So, under the influence of extreme stimuli, adaptive stress reactions develop in the body, aimed primarily at mobilizing energy resources. Glucocorticoid hormones, the release of which is mediated by the activation of GGNS, as well as catecholamines, trigger additional ways of energy exchange. Blood flow in the brain increases, aerobic oxidation of glucose and glycolysis increase, and ketone bodies are used as an energy substrate in addition to glucose, which causes acidification of nerve tissue and blood flowing from the brain. Regardless of the type of stressor, people who are waiting for alarm signals and with preoperative stress revealed a significant increase in SCP, reflecting brain acidification. It should be noted that hyperventilation, which is also stress, is accompanied by a natural increase in SCP (section 6.4). The increase in SCP is associated with the activation of GNSS, as evidenced by the relationship between SCP and cortisol level. In people under stress, the tone of the sympathetic nervous system prevails. The relationship of SCP in the frontal region with the Kerdo index indicates the participation of the frontal parts of the brain in autonomic regulation.
As already mentioned, stress, on the one hand, has an adaptive value for the body, and on the other, it can cause adverse effects. Long-term acidosis is a danger to neurons, since a decrease in pH disrupts the respiratory chain of mitochondria, which enhances the formation of oxygen free radicals. With oxidative stress, calcium intake to neurons increases, which activates enzymes that cause degradation of cellular structures. With significant acidosis, apoptosis is triggered – programmed cell death.
The use of the method of registration and analysis of AMR allows you to control changes in the CRR, which can be used to prevent the damaging effects of stress on the brain.