V.N. Chikhman1, S.D. Solnushkin2, V.O. Molodtsov3, V.Y. Smirnov4,
O.A. Lyubashina5, I.B. Sivachenko6

1,2,5,6 Pavlov Institute of Physiology, Russian Academy of Sciences (St.-Petersburg, Russia)

3,4 St. Petersburg State Electrotechnical University "LETI" named after V. I. Ulyanov (Lenin) (St.-Petersburg, Russia)

The study of the functional relationships of various formations of the brain and internal organs is one of the areas of experimental physiological research. In electrophysiological experiments on anesthetized rats, the responses of neurons of the stem structures to visceral pain stimulation are recorded, and changes in neuronal reactions during electrical stimulation of the superior brain formations are studied. In the course of the experiment, it is desirable, along with the registration of neuronal activity, to simultaneously monitor the level of systemic blood pressure and respiratory movements with the possibility of real-time assessment of changes in these parameters during electrical stimulation of various brain structures. Registration of impulse activity of neurons is carried out using a tungsten microelectrode, amplifier and computer sound card using standard operating system tools for inputting signals from a microphone and saving wav files. Electrical stimulation of the hypothalamus is realized by manually supplying a trigger pulse using the A320 electrostimulator (World Precision Instruments, USA). The aim of our work was to develop hardware and software for parallel registration and display of signals of neuronal activity, pressure and respiration, as well as programmable control of stimulation. Known complexes for the registration of biosignals, for example, PowerLab (ADInstruments ltd), which allow the measurement of the above parameters of vital activity. However, these complexes are characterized by excessive complexity and high cost. Using them in a functioning installation is not economically efficient. To measure the parameters of the vital activity of laboratory animals during the experiment on the existing operating installation, the MD300 device was developed and implemented, containing two channels for recording signals taken from bridge pressure sensors, and an output channel for pulse shaping for starting the stimulator.

To register blood pressure, we used an MLT0670 sensor (ADInstruments, Australia), and to register breathing parameters, we used an MPX53GP sensor (Freescale Semiconductor, USA) installed in the respiratory tract of a rat. The MD300 device, in addition to measuring pressure signals, provides the formation and issuance of a control pulse at the command of the computer to start the specialized electrostimulator A320. For the purpose of high-quality monitoring of blood pressure and respiration indicators during the experiment, the signals taken from the pressure sensors are sampled in the MD300 device simultaneously with a frequency of 125 Hz. For signal sampling, an 8-channel sigma-delta ADC ADS131M08 (Texas Instruments, USA) was used, which ensures operation with low-level sensors, in our case with MLT0670 with a sensitivity of 16.5 μV / mm Hg.

The main unit of the MD300 device is the STM32F042F4 microcontroller (STM, Switzerland), which provides the transfer of the ADC output codes to the computer in accordance with the USB interface protocol. The microcode for the functioning of the microcontroller was developed in C ++ in the IAR Embedded Workbench for ARM environment (IAR, Sweden) using the USB library created by STM.

The signal processing program NPB (neural, pressure, breathing) is written in the Borland Delphi 7 environment, uses the JEDI VCL component library that implements access to HID compatible USB devices, and the free Mitov Software library. The NPB program includes two blocks – signal registration and delayed processing. The registration block allows you to set up the general parameters of the experiment and set the initial setting values for signal conversion. To configure the parameters, the visual components are provided to select the units for displaying signals (mV or mm Hg), to set the values of the time parameters of the experiment, to set the mode of a single start of the stimulator or the start of a series of stimulating impulses.

The "start" button starts the process of registering signals. In the two graphic fields, impulse activity is displayed in real time in the form of an initial signal and after processing by the RMS software component (root mean square), which allows you to visually observe clearly pronounced peaks of neuronal activity in the signal. The lower two fields display blood pressure and airway pressure signals. Oscilloscope mode is implemented in all four fields.

When you press the "parameters" button, the window for setting the parameters of sampling of analog signals and stimulation is called. The components in this window allow you to set the sampling rate and bit depth of the transformation of the signal of neuronal activity, gain factors and sampling frequency for signals taken from respiration and blood pressure sensors, set the stimulation parameters (time of stimulation, duration and number of stimulations).

The registered signals are saved in the internal database of the program.

The graphical interface of the next block includes three windows for displaying signals of neural activity, pressure and respiration stored in the internal database of the program.

In the graphic window "Activity" in the full amount of recording time (not in the oscilloscope mode), the signal of neuronal activity registered in the base is presented. The graphical windows "pressure" and "breathing" show the registered signals from the sensors and the amplitude-frequency spectrum of the corresponding signal, obtained using the free Basegroupe library, the LowPathFilter component.  

The graphs of the displayed processes are marked with reference lines corresponding to the beginning and end of stimulation. With the help of the window components (in the lower left part) it is possible to save the registered data as binary, text files for further processing or their transfer to Excel.

The developed and implemented tools are used in experimental research at the Pavlov Institute of Physiology RAS.

Chikhman V.N., Solnushkin S.D., Molodtsov V.O., Smirnov V.Y., Lyubashina O.A., Sivachenko I.B. Control of the vital parameters of the experimental animal. Biomedicine Radioengineering. 2022. V. 25. № 1. Р. 53-61. DOI: https://doi.org/10.18127/j15604136-202201-06 (In Russian).

1. Panteleyev S.S., Sivachenko I.B., Busygina I.I., Lyubashina O.A. Effekty stimulyatsii infralimbicheskoy kory na reaktsii neyronov kaudalnoy ventrolateralnoy retikulyarnoy formatsii. vyzvannyye notsitseptivnym razdrazheniyem tolstoy kishki krysy. Rossiyskiy fiziologicheskiy zhurnal im. I.M. Sechenova. 2020. T. 106. № 12. S. 1524–1540. DOI: 10.31857/S0869813920120067 (in Russian).
2. Panteleev S.S., Sivachenko I.B., Lyubashina O.A. The Buspirone-dependent Abdominal Pain Transmission Within the Nucleus Tractus Solitarius in the Rat. Neuroscience. 2021. V. 452. P. 326–334. DOI: 10.1016/j.neuroscience.2020.11.032
3. Lyubashina O.A., Sivachenko I.B., Busygina I.I. Amigdalofugalnaya modulyatsiya vistseralnoy notsitseptivnoy transmissii v kaudalnoy ventrolateralnoy retikulyarnoy oblasti prodolgovatogo mozga krysy v norme i pri kishechnom vospalenii. Rossiyskiy fiziologicheskiy zhurnal im. I.M. Sechenova. 2021. T. 107. № 10. S. 1–16. DOI: 10.31857/S086981392110006X (in Russian).
4. Lyubashina O.A., Sivachenko I.B., Busygina I.I., Panteleev S.S. Colitis-induced alterations in response properties of visceral nociceptive neurons in the rat caudal medulla oblongata and their modulation by 5-HT3 receptor blockade. Brain Res. Bull. 2018. V. 142. P. 183–196. DOI: 10.1016/j.brainresbull.2018.07.013
5. Panteleyev S.S., Chikhman V.N., Molodtsov V.O. Avtomatizirovannaya elektrofiziologicheskaya ustanovka dlya issledovaniya motornoy funktsii zheludochno-kishechnogo trakta anestezirovannoy krysy. Fiziologicheskiy zhurnal. 1996. T. 82. № 4. S. 135–140. (in Russian).
6. Molodtsov V.O., Chikhman V.N., Solnushkin S.D. Apparatno-programmnoye obespecheniye ARM fiziologa. Pribory i sistemy upravleniya. 1999. № 3. S. 15–19. (in Russian).
7. Molodtsov V.O., Solnushkin S.D., Chikhman V.N. Ustroystvo dlya izmereniya signalov v elektrofiziologicheskom eksperi-mente. Pribory i tekhnika eksperimenta. 2011. № 5. S. 163–165. (in Russian).
8. Molodtsov V.O., Smirnov V.Yu., Solnushkin S.D., Chikhman V.N. Apparatno-programmnyye sredstva dlya fiziologicheskikh eksperimentov. Biomeditsinskaya radioelektronika. 2014. № 12. S. 57–63. (in Russian).
9. Solnushkin S.D., Chikhman V.N. Programmnyye sredstva dlya analiza impulsnoy aktivnosti v neyroeksperimente. Biomedi-tsinskaya radioelektronika. 2015. № 6. S. 35–39. (in Russian).
10. Solnushkin S.D., Chikhman V.N. Organizatsiya vychislitelnykh protsessov dlya fiziologicheskikh issledovaniy dykhaniya. Bio-meditsinskaya radioelektronika. 2017. № 3. S. 48–54. (in Russian).
11. Chikhman V.N., Molodtsov V.O., Smirnov V.Yu., Solnushkin S.D., Vaydo A.I. Ustroystvo dlya elektrostimulyatsii laborator-nykh zhivotnykh. Pribory i tekhnika eksperimenta. 2019. № 5. S. 160–161. (in Russian).
12. Chikhman V.N., Solnushkin S.D., Molodtsov V.O., Smirnov V.Yu. Ustroystvo dlya elektrorazdrazheniya laboratornykh zhivot-nykh na osnove ispolzovaniya generatora toka. Pribory i tekhnika eksperimenta. 2020. №2. S. 161–162. (in Russian).
13. Molodtsov V.O., Smirnov V.Yu., Solnushkin S.D., Chikhman V.N. Apparatno-programmnoye obespecheniye povedencheskogo eks-perimenta. Biomeditsinskaya radioelektronika. 2021. № 1. S. 5–23. (in Russian).
14. Aziz N., Simonetta G., Forrester K. Review article. Recent developments in data recording systems for physiology. Pak. J. Physiol. 2006. V. 2(1).
15. Aleksandrov V., Merkuryev V., Ivanova T. i dr. Korkovyy kontrol refleksov Geringa-Breyera u anestezirovannykh krys. Eur. J. Med. Res. 2009. V. 14. № 1 DOI: 10.1186/2047-783X-14-S4-1 (in Russian).
16. Molodtsov V.O., Smirnov V.Yu., Solnushkin S.D., Chikhman V.N. Ustroystvo dlya registratsii fiziologicheskikh parametrov laboratornykh zhivotnykh. Pribory i tekhnika eksperimenta. 2022. № 1. S. 159–161. (in Russian).
17. https://mitov.com
18. Rangayyan R.M. Analiz biomeditsinskikh signalov. Prakticheskiy podkhod. M.: Fizmatlit. 2007. 440 s. (in Russian).