Evoked Bioelectrical Activity of Efferent Fibers of the Sciatic Nerve of White Rats in Experimental Menopause

The aim of our work was analysis of the bioelectrical activity of the sciatic nerve efferent fibers in experimental menopause condition. The study was performed on 25 sexually mature female Wistar rats weighing 180–250 g, that were divided into two groups – control (n=12) and experimental (n = 13). In order to reproduce hypoestrogenemia, we provide ovariohisterectomia. Medial laparotomy without ovariohisterectomia was performed to the animals of control group for exception the impact of stress on the postoperative course of the experiment. Both groups of animals were kept in standard vivarium conditions (22±2 °C, light / dark cycle was 12/12 hrs.) at a standard diet during 120 days, whereupon acute animal experiments were carried out. Sodium thiopental at a dose of 50 mg / kg was used for total anesthesia. Isolated sciatic nerve was placed on bipolar stimulating electrodes, and were submerged in vaseline oil to prevent drying. The nerve was stimulated by single square pulse with duration of 0.3 ms and amplitude of 1 to 5 thresholds. The registration of the induced action potential of the proximal portion of ventral roots with using bipolar electrodes. Threshold, chronaxia, latency, amplitude and duration of the action potential were analysed. Refractory phenomenon was investigated by applying paired stimuli at intervals of 2 to 20 ms. Electrical stimulator, amplifier, analog-to-digital converter, PC were used. The reliability of the data was assessed using parametric methods (Student test) and nonparametric statistics (Mann-Whitney test). Changes recognized statistically significant at p<0.05. All experimental procedures were performed according to the European Communities Council Directive of 24 November 1986 (86/609 / EEC), euthanasia was performed by administering a lethal dose of thiopental sodium. In the condition of long-term hypoestrogenemy appearance threshold of activate of nerve fibers decreased to 55.32±7.69%, chronaxy of induced potential increased to 115.09±2.67%, the latent period of action potential increased to 112.62±1.74% compared with the control animals (p<0.01). In condition of paired stimuli the amplitude of response to the testing stimulus in animals with ovariohysterectomy at intervals 3 and 4 ms was 61.25±36.45% and 53.48±18.64% (p<0.05) respectively. Thus, provided early emergence and existence of long-term estrogen deficiency an increase in excitability of nerve fibers on the background of deteriorating performance and reduce time lability. Prospects for further research. Identified changes we urge a more detailed study of the processes taking place in the ventral roots CM in terms hipoestrohenemia particular state of synaptic transmission and monosynaptic response of the structure that will be considered in our further studies.