Some characteristics of unit activity in the frontal cortex of alert monkeys

Spontaneous activity of frontal cortical neurons (middle part of sulcus principalis) and their responses to stimuli of different biological significance were studied in alert monkeys. The region studied is characterized by a lower level of spontaneous activity than the motor cortex. Fluctuations in the level of spontaneous activity are connected with changes in the experimental situation. Two types of unit responses were distinguished to repetitive stimulation: preservation of responses and habituation. The type of unit response depends on the relationship of the stimuli to the animal's motivational sphere.A. A. Ukhtomskii Physiological Research Institute, A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 3–12, January–February, 1980.     

Conditions of appearance of off responses of sensomotor cortical neurons to photic stimulation in cats

In acute experiments on cats under chloralose anesthesia (70 mg/kg) unit activity was recorded extra- and intracellularly in the sensomotor cortex (areas 4 and 6) during prolonged (up to 1000 msec) photic stimulation. Responses of on-off type were generated by 100% of neurons tested to photic stimuli whose duration corresponded to the recovery cycle of functional changes after a single flash, determined by the paired stimulation method. Cutaneous stimulation affected the appearance of the photic off response if it led to a spike discharge of the neuron before the off response. It is suggested that IPSPs of cortical neurons largely determine both the duration of the cycle of functional recovery after a single flash and also differences in the pattern of generation of the off response and its interaction with responses to cutaneous stimulation.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 355–360, July–August, 1977.     

Mitochondria as a target for neuroprotection

Despite all the efforts of modern medical and biomedical sciences, the effective therapeutic treatments that would restore the brain functions lost after stroke have not been found yet. At the same time, experimental preclinical studies revealed an arsenal of effectors having potential for clinical applications. Identification of the key signaling pathways, both damaging and protective, can accelerate the development and implementation of new effective neuroprotectors. One of the key elements of these pathways is mitochondrion. In this context, we studied various therapeutic approaches to the treatment and prevention of cerebral ischemia, which are aimed at modulation of mitochondrial functions. The spectrum of tested neuroprotectors included antioxidants, uncouplers of respiration and phosphorylation, as well as ischemic, remote, and pharmacological preconditioning. Their efficacy and therapeutic windows were compared and the possibility of combining different methods in order to maximize their efficiency was considered.     

Investigation of habituation reaction of neurons of the cat motor cortex

The neuronal and total surface activity of the cortical representation of the motor analyzer in the region of the posterior sigmoid gyrus of the cat brain in response to rhythmical light, sound, and electrical stimuli and their complexes was analyzed. Two groups of neurons were found, of which the first is characterized by a gradual decrease in the number of peaks in the response and by their subsequent disappearance and the second by the absence of a discharge in response to stimulation and by its development before the application of the next stimulus. The first group was comprised of neurons which do not have background activity and the second was made up of neurons with a background activity of 0.4–3.7 imp/sec. This reorganization of the activity of cortical neurons in response to rhythmical stimulation is considered to be a habituation phenomenon.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 245–251, May–June, 1971.     

Studies on projections of somatic afferentation in the neocortex of the hedgehog Erinaceus europaeus]

Cortical projections of the somatic system in the hedgehog cortex were studied by means of the evoked potential (EP) technique. The EPs were shown to arise at a large area of the lateral cortex, the area in question being enlarged under chloralose anaesthesia. In the focus of projection of corresponding modalities the EPs posessed the least latency. Functional differences in the EP generation system both in the focus of projection and outside it are discussed. The wide EPs spreading in the lateral cortex as well as the presence of relatively differentiated projections is supposed to depend on the afferent volley dispersion to the polysynaptic pathways at the thalamic level. Considerable overlapping of sensory projection zones in the cortex is conditioned by the latter and indicates low degree of the somatic analyser organization.     

Dysfunction of kidney endothelium after ischemia/reperfusion and its prevention by mitochondria-targeted antioxidant

One of the most important pathological consequences of renal ischemia/reperfusion (I/R) is kidney malfunctioning. I/R leads to oxidative stress, which affects not only nephron cells but also cells of the vascular wall, especially endothelium, resulting in its damage. Assessment of endothelial damage, its role in pathological changes in organ functioning, and approaches to normalization of endothelial and renal functions are vital problems that need to be resolved. The goal of this study was to examine functional and morphological impairments occurring in the endothelium of renal vessels after I/R and to explore the possibility of alleviation of the severity of these changes using mitochondria-targeted antioxidant 10-(6′-plastoquinonyl)decylrhodamine 19 (SkQR1). Here we demonstrate that 40-min ischemia with 10-min reperfusion results in a profound change in the structure of endothelial cells mitochondria, accompanied by vasoconstriction of renal blood vessels, reduced renal blood flow, and increased number of endothelial cells circulating in the blood. Permeability of the kidney vascular wall increased 48 h after I/R. Injection of SkQR1 improves recovery of renal blood flow and reduces vascular resistance of the kidney in the first minutes of reperfusion; it also reduces the severity of renal insufficiency and normalizes permeability of renal endothelium 48 h after I/R. In in vitro experiments, SkQR1 provided protection of endothelial cells from death provoked by oxygen–glucose deprivation. On the other hand, an inhibitor of NO-synthases, L-nitroarginine, abolished the positive effects of SkQR1 on hemodynamics and protection from renal failure. Thus, dysfunction and death of endothelial cells play an important role in the development of reperfusion injury of renal tissues. Our results indicate that the major pathogenic factors in the endothelial damage are oxidative stress and mitochondrial damage within endothelial cells, while mitochondria-targeted antioxidants could be an effective tool for the protection of tissue from negative effects of ischemia.