Analysis of the Relationship between Activity of the Reticular Formation of the Medulla Oblongata and the Respiratory and Cardiovascular Systems in Rats under Painful Stimulation

Using a method based on averaging the conditional probabilities of recurrence intervals, a comparative analysis was performed to estimate the direction of coupling between different physiological rhythms (fluctuations in blood pressure, respiration, and neuronal activity in the reticular formation of the medulla oblongata) in two groups of anesthetized rats with or without painful stimulation. Different variants were observed for the directions of coupling between the rhythms. A statistically significant unidirectionality of coupling was detected with most of the data obtained from rats of the control group and rats with experimentally induced colitis. Painful stimulation did not affect the direction of coupling, but slightly reduced the amount of data with unidirectional coupling. Rhythms associated with the cardiovascular system (blood pressure variability) were controlled by rhythms of the respiratory system, and the respiratory rhythm controlled the variability of neuronal activity in the reticular formation of the medulla oblongata.