Methods for calculating the stereotaxic coordinates of rat brain structures by pixel coordinates of the image obtained by confocal and two-photon laser scanning microscopy.

BACKGROUND: There is a challenge to determine stereotaxic coordinates of a target structure with the accuracy, comparable to their size, when imaging the rat brain through cranial windows using confocal (multiphoton) microscopy in vivo. Some methods based on the estimation of the linear displacement from the intersections of the cerebral vessels are most often used for these purposes, but their accuracy can be improved. NEW METHOD: A new method for converting pixel coordinates of points of interest on an image obtained in two-photon microscopy into stereotaxic ones using quadratic approximation with L2 regularization has been developed. A comparative analysis of several methods for converting pixel coordinates into stereotaxic ones was carried out. The current study is aimed to select a method which minimizes the error of coordinate conversion within the a priori specified threshold value. RESULTS: A method for determining the stereotaxic coordinates of each pixel in an image obtained by laser scanning in two-photon and / or confocal modes with an accuracy of several tens of microns is proposed. COMPARISON WITH EXISTING METHOD(S): It is shown that the error probability of the most common method based on calculating the points of interest coordinates as displacements relative to the selected vessels intersections can be reduced by using the quadratic approximation with L2 regularization. Our proposed method allows us to improve the accuracy of determining the coordinates of points of interest on 10-30 µm. CONCLUSIONS: The proposed approach will be useful in research where precise positioning of microelectrodes, sensors, etc. for implantation in specified brain structures or groups of neurons determined by functional mapping is required.

GABAergic Mechanism of Anticonvulsive Effect of Chemical Agent RU-1205.

The study examined the effect of 9-(2-morpholinoethyl)-2-(4-fluorophenyl)imidazo[1,2-α] benzimidazole dihydrochloride (RU-1205) on the latency of seizures provoked by corazol, bicuculline, or picrotoxin. This agent (10 and 20 mg/kg) increased the seizure latency in the experimental models of epileptogenesis. The blockers of GABAA and GABA A -ρ receptors picrotoxin and (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid, respectively, were employed to study the effects of RU-1205 on electrical activity of somatosensory cortical neurons and on formation of pathological rhythms in the rat brain. RU-1205 inhibited the focal background rhythm and eliminated the epileptiform activity, which can be mediated by interaction with GABAA receptors.

[Influence of GABA(C)-Receptor Antagonist on Formation of Evoked Potentials in Columns of the Rat Somatosensory Cortex].

Microelectrode studies of evoked potentials (EP) in neuronal column of rats barrel cortex show activating action of selective GABA(C)-receptor antagonist 1,2,5,6-tetrahydropyridin-4-yl-methylphosphinic acid (TPMPA) mainly on secondary components of EP of supragranular afferent layers of column compared to the efferent infragranular layers. These data suggest localization of GABA(C)-receptors on pre- synaptic terminals of thalamo-cortical glutamatergic afferents and ascending apical dendrites of pyramidal cells. A blockade of GABA(C)-receptors with the selective antagonist TPM PA leads to dose-dependent afferent depolarization with development of presynaptic inhibition and suppression of primary components of EP GABA(C)-receptors blocker produces different effects on secondary components of EP in supragranular layers of the cortex caused by the development of neuronal after hyperpolarization followed by high-amplitude primary response and afterdepolarization followed by low-amplitude primary responses with subsequent activation of different voltage-gated channels and formation of different level of cortical direct current potential gradients.

[GABAergic receptor system and its role in system activity of the brain].

In the review the analysis of structural and functional features of the main types of GABA-receptors and their distribution in various regions of a brain of vertebrata is carried out. Questions of an involvement of various types of GABA-receptors in various processes of brain activity are investigated. The data concerning tonic GABAergic inhibition in CNS, connected with extrasynaptic receptors, are shown. The physiological importance of mechanisms of tonic inhibition is discussed.

[The role of GABAA and GABAB receptors in formation of evoked potentials in the barrel cortex of rats].

By means of local microapplication of GABA, picrotoxin and CGP 52432, different roles of GABAA and GABAB receptors in the geneses of primary and secondary components of evoked potentials in the somatosensory barrel cortex of rats were shown. The authors conclude that the aftereffect rhythmical components of the evoked potentials are caused by the local pacemaker mechanisms based on endogene properties of barrel neurons.