Dynamics of Electrical Activity of Olfactory Structures under Conditions of Calypsol / Ketamine Anesthesia
Authors: Ilyukha L. M. 
Published: January 2022

Introduction. In this study, we have characterized high-frequency and low-frequency oscillations at several stages of olfactory processing under calypsol anesthesia in albino rats. While monitoring the animal's respiration, we also obtained field potentials from the olfactory bulb and piriform (olfactory) cortex and simultaneously recorded membrane potentials in piriform cortex pyramidal cells. Manifestations of the considered specific high-frequency components of electrical activity of rhinencephaly structures, in particular olfactory-amygdala rhythm and high-frequency synchronized activity, are obviously the resultof complex interaction of peripheral and central excitation mechanisms at the level of olfactory bulbs. We believe this finding has important functional as well as evolutionary implications.Purpose. To investigate the temporal dynamics of the manifestations of the phenomena of electrical activity of the olfactory bulb of rats and its changes under calypsol anesthesia.Methods.Stereotactic and electroencephalographic methods, correlation-spectral and coherent analysis of the obtained records of electricalactivity of the brain structures were used to study the bioelectrical activity of olfactory structures of the brain of experimental animals.The work was performed in a chronic experiment on 12 outbred white rats, males weighing 200 g. A premedication cocktail and calypsol at a rate of 25 mg / kg of animal weight were used for anesthesia. Implantation control was carried out according to specific patterns of electrical activity of the studied structures.The bioelectrical activity of the brain of each animal was studied for 10-20 days, followed by morphological control.Results. Olfacto-amygdala rhythm is registered against the background of polymorphic activity on the peak of respiratory waves in the form of spindle-shaped flashes of high-frequency oscillations in the range of 52-95 Hz, variable in amplitude. Simulation of the sustained suppression state of olfacto-amygdala rhythm in rhinencephalic structures was achieved using the technique of transferring animals to a state of deep ketamine (calypsol) anesthesia. This allowed not only to "exclude" flashes of olfactory-amygdala rhythm, but also to significantly suppress the high-frequency components of the spectra of electrical activity of olfactory bulbs, to increase the manifestation of low-frequency components (p <0.01-0.05) and to probably reduce the index of high-frequency waves (р<0.05). ISSN 2076-5835. Вісник Черкаського університету. 2021 No247Deep calypsol anesthesia caused differences in the spectra of electrical activity of olfactory bulbs at different depths of discharge only in terms of the spectral power density of the slow-wave range. At the same time, identical probable (p <0.05) suppression of high-frequency components of electrical activity of olfactory bulbs was observed.Under these conditions, the preservation of high-frequency components of the spectrum (unformed in spindles) in the electrical activity of olfactory bulbs at the border of mitral and granular cells was observed even under conditions of sharp depression of -activity in ECoG and identical dominance of high-amplitude low-frequency oscillations in the amygdala.Originality. The influence of narcotic substances on the dynamics of manifestations of the phenomena of electrical activity of rhinencephalic structures: respiratory waves, olfacto-amygdala rhythm, polymorphic activity, is revealed.Conclusions.It is expedient to use the following amplitude-time patterns for objective characterization of total electrical activityof olfactory structures of rats, whichprobably differ in power-frequency characteristics: polymorphic desynchronized activity, respiratory waves, olfacto-amygdala synchronous rhythm and high-frequency synchronous rhythm.Polymorphic activity is normally represented by low-amplitude oscillations (10-200 μV) in a wide frequency range (10-150 Hz) with a set of dominant extremes. Оlfactory-amygdala rhythmis registered against the background of polymorphic activity on the peak of respiratory waves in the form of spindle-shaped flashes of high-frequency oscillations in the range of 52-95 Hz, variable in amplitude.Experimental modeling of the state of stable suppression of olfacto-amygdala rhythm and high-frequency synchronized activity in the electrical activity of olfactory bulbs (under colipslol / ketamine anesthesia) revealed suppression of manifestations of high-frequency components of the spectrum, indicating the important role of centrifugal effects inthe mechanisms of olfactory rhythm generation.Key words:electrical activity, olfactory bulb, fast oscillations, slow oscillations, excitation, anesthesia