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Technologies for multichannel electrophysiology are experiencing astounding growth. Numbers of channels reach thousands of recording sites, systems are often combined with electrostimulations and optic stimulations. However, the task of design the cheap, flexible system for freely behaving animals without tethered cable are not solved completely. We propose the system for multichannel electrophysiology for both rats and mice. The system allows to record unit activity and local field potential (LFP) up to 32 channels with different types of electrodes. The system was constructed using Intan technologies RHD 2132 chip. Data acquisition and recordings take place on the DAQ-card, which is placed as a back-pack on the animal. The signal is amplified with amplifier cascade and digitalized with 16-bit ADC. Instrumental filters allow to filter the signal in 0.1–20000 Hz bandwidth. The system is powered from the mini-battery with capacity 340 mA/hr. The system was validated with generated signals, in anaesthetized rat and showed a high quality of recordings.

Electrophysiological recordings of brain activity show both oscillatory dynamics that typically are analyzed in the time-frequency domain to describe brain oscillatory phenomena and scale-free arrhythmic activity defined as neural noise. Recent studies consider this arrhythmic fractal dynamics of neural noise as a sensitive biomarker of a number of cognitive processes, activity of neurotransmitter systems, changes that accompany neurodegenerative and psychiatric disorders including alcohol use disorder. We tested the changes in neural noise induced by acute alcohol intoxication in the lateral septum for the entire spectrum (1–200 Hz) of local field potential signal and for frequency specific ranges (delta, theta, beta, gamma and epsilon bands). Five male Wistar rats were implanted with intracranial electrodes and local field potential signal was measured for baseline activity and activity induced by acute ethanol intoxication (2 g/kg). Change in neural noise dynamics was assessed as a change in the slope of linear regression fit of power spectral density curves in double logarithmic scale. In our study alcohol resulted in lower incline of scale-free activity in the lateral septum for high frequency range and for the whole spectrum, which is interpreted generally as increase in neural noise and change in neuronal processing in a more stochastic way initiated by the acute alcohol intoxication. At the same time, we observed decrease in neural noise for low frequency range. The observed changes may be related to the shift of the excitatory-inhibitory balance towards inhibition and changes in neurotransmission mostly in the GABAergic system. Scale-free activity was sensitive in the conditions of acute alcohol intoxication, therefore to understand its role in alcohol use disorder we need more data and studies on the underlying processes. Future studies should include simultaneous recordings and analysis of arrhythmic dynamics with the oscillatory and multiunit spiking activity in the lateral septum. It can reveal the contribution of different-scale processes in changes driven by acute alcohol intoxication and clarify the specific electrophysiological mechanisms.

Annotation. Alcohol is a one of the most frequently consumed substances of abuse, which can cause addiction or alcohol use disorders (AUDs). Alcohol addiction leads to decrease of the life quality of patients and considerable economic burden. Neuronal mechanisms of addiction are intensively studied. One of the most important systems involved in this process is a brain reward system that includes lateral septum (LS). Additionally alcohol consumption changes activity of the neurotransmitter systems including the nitric oxide (NO). Recent studies for blockage of nitric oxide synthase (NOS) for cocaine addiction and late stages of AUDs demonstrated that a group of the substances known as blockers of NOS can be referred to as candidates for alcohol addiction therapy. The aim of our research was to investigate histochemical characteristics of NO-system in LS, its response to acute alcohol intoxication including or excluding neuronal NOS (nNOS) blockage with selective inhibitor – 7-nitroindazole (7-NI). This study involved three experimental groups of animals (control group (n=4), group with acute alcohol intoxication (n=4), group of nNOS blockage with acute alcohol intoxication (n=4)). For statistical analysis, one-way Kruskal-Wallis test was implemented to reveal differences between groups (Matlab, Mathworks). We have identified NOS-positive structures in LS consisting of big neurons, medium/small neurons and nerve fibers. Acute alcohol intoxication activated subpopulations of NOS-positive medium/small neurons and nerve fibers. Moreover, we determined that ethanol-induced changes can be blocked with selective nNOS inhibitor 7-NI.

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