Фармация и фармакология (Пятигорск) (Nov 2018)
METHOD FOR DETERMINING THE UPPER LIMIT OF CEREBRAL AUTOREGULATION IN RATS
Abstract
The main objective of the phenomenon of cerebral autoregulation is to maintain a constant cerebral blood flow rate with changes in systemic arterial pressure in the range of 50 mmH up to 150 Mmhg. To study this phenomenon, there are two approaches: dynamic and static. The dynamic approach is known to the study autoregulation, can indirectly characterize this phenomenon with the help of calculated indicators, and the described static methods can characterize only the lower limit of autoregulation of cerebral blood flow. The aim of the study was to develop a method for determining the value of pressure at the “breakdown” point of the upper limit of cerebral hemodynamics autoregulation. Materials and methods. The experiment was carried out on male rats of the Wistar line weighing 200–250 g, kept in standard vivarium conditions. The essence of the method of establishing the upper “breakdown” point of the autoregulatory mechanisms of cerebral circulation is pumping blood from the femoral artery to both carotid arteries by means of a peristaltic pump, while controlling the pressure and cerebral blood flow velocity. In order to avoid blood loss as a result of blood flow redistribution, external carotid arteries were ligated. The pressure was measured by the direct method. Since the pressure is created by the resistance of the cerebral vessels, it can be measured at the entrance by specially modeled carotid catheters. Cerebral blood flow velocity was measured by an ultrasound doppler scanner using MDK-Minimax Doppler v .2.1 program. To establish the possibility of using this method in the study of the influence of substances on the autoregulation of cerebral circulation, the effect of nicergoline on this phenomenon was studied. The drug was administered as a suspension intragastrally to rats 1 hour before metering. The results and discussion of the experiment showed that in intact rats the “breakdown” point of the upper limit of autoregulation was recorded at 165.0 ± 3.4 Mmhg (M ± m). Statistical processing of the obtained data indicates the normal distribution of the sample and the validity of the developed method. The introduction of nicergoline led to the increase in pressure at which there was a “breakdown” of the autoregulation mechanisms to 181.7 ± 4.7 Mmhg, which was significantly higher than the values of the intact group. Conclusion. As a result of the experiment on male rats, a valid method was developed for determining the blood pressure value at the highest point of “breakdown” of cerebral hemodynamics autoregulation and it was established that nicergoline shifts the functioning limit of the autoregulation phenomenon to higher values.
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