The purpose of this study was to investigate changes in the excitability of motor nerve fibers in conditions of prolonged androgen deficiency and the modification of the evoked response parameters. The study was performed on male Wistar rats of 5 - 6 months old and weighing 180 - 260 grams, they were divided into experimental (n = 19) and control (n = 14) groups. The model was created by bilateral orchectomy. Both groups of animals were kept under standard vivarium conditions (t <$E22~symbol С~2~symbol Р roman C>, light/dark cycle - 12/12 h) on a standard diet for 120 days, after which the animals were engaged in an acute experiment. The evoked potentials of action were recorded using bipolar electrodes superimposed on the peripheral section of the sciatic nerve when stimulated with ipsilateral ventral root L5 by pulses of 0,3 ms duration and force from 1 to 5 thresholds. Excitation threshold, chronoxia, latency period, amplitude and response duration were analyzed. The involvement of different threshold nerve fibers in the excitation process was investigated by applying stimuli from 1,1 to 2 thresholds. While analyzing the response of nerve fibers to the application of paired stimuli with an interval of 2 to 20 ms, changes in refractivity were investigated. Statistical processing of the study materials was performed by using biometric analysis methods implemented in EXCEL-2003 and STATISTICA 6.1 (StatSoft Inc., Serial No. AGAR909E415822FA) licensed packages. For calculating the obtained results, the calculation of visibility as a percentage, arithmetic mean and error of the mean (<$Eroman {M~symbol С~m}>) was used. Probability was estimated by using parametric statistics methods (Student's t-test). Changes in indicators were considered probable at p << 0,05. The threshold of occurrence of the total response of nerve fibers was <$E664,29~symbol С~0,75> %, chronoxia <$E71,90~symbol С~1,94> %, latency period <$E172,73~symbol С~2,63> %, total duration <$E125,53~symbol С~1,13> % as compared to the control group. The response amplitude increased by <$E76,42~symbol С~5,88> % (p << 0,001). When applied to the sciatic nerve of a single stimulus of increased intensity, the dependence curve for animals from the experimental group showed a faster increase in the amplitude of the evoked total action potential. Significant changes (p << 0,001) were observed when applying stimuli from 1,1 to 1,6 P, which may indicate an increase in the excitability of low- and mid-threshold nerve fibers within the ventral root. When paired stimuli were used, the response amplitude response to the test stimulus in animals with ovariohysterectomy was observed at intervals of 2 to 4 ms, whereas in the control group it occurred only at an interval of 20 ms, indicating a significant shortening of the refractory neurite period. Thus, the long-existing hypoandrogenemia has a considerable, though paradoxical effect on the functioning of efferent somatic nerve fibers, causing a decrease in their excitability against the background of a significant increase in lability as well as an increase in the amplitude and duration of the evoked response.

• Родинський Олександр Георгійович (медичні науки)
• Ткаченко Світлана Сергіївна (1984–) (технічні науки)
• Ткаченко Сергій Сергійович (медичні науки)
• Ткаченко Світлана Сергіївна (історичні науки)

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