Mats Vn

Unrestrained walking in cats with medial pontine reticular lesions

The early postoperative effects of lesions, aimed to destroy the caudal pole of the nucleus reticularis pontis oralis (NRPO) and the rostral pole of the nucleus reticularis pontis caudalis (NRPC), were tested in freely moving cats, walking at moderate speed (0.4-1.0 m/s). In cats in which these structures were partly or completely destroyed, the main effect of lesions was an impairment of fore-hindlimb coordination, as shown by a change in the relationships between the lateral and diagonal time shift durations and the step cycle duration. In the second week after the surgery the values of the slopes of linear regressions relating these variables were markedly changed as compared to the preoperative data. The results suggest that the NRPO and NRPC are involved in maintaining the proper forehindlimb coordination during unrestrained locomotion in cats.

Neuron activity in the anterolateral motor cortex in operant food-acquiring and alcohol-acquiring behavior

The interactions of the neuronal mechanisms of food-acquiring behavior and newly formed operant alcohol-acquiring behavior were studied by recording the activity of individual neurons in the anterolateral area of the motor cortex in chronically alcoholized rabbits. Adult animals learned food-acquiring behavior in a cage with two feeders and two pedals, in the corners (the food in the feeders was presented after pressing the corresponding pedal). After nine months of chronic alcoholization, the same rabbits learned an alcohol-acquiring behavior in the same experimental cage (gelatin capsules filled with 15% ethanol solution were placed in the feeders instead of food). Analysis of neuron activity showed that the set of neurons involved in supporting food-acquiring and alcohol-acquiring behaviors overlapped, though not completely. These experiments not only help us understand the neuronal mechanisms of the newly formed and the previously formed behaviors, but also facilitate the development of concepts of the similarity of the neuronal mechanisms of long-term memory and long-term modifications of the nervous system, occurring in conditions of repeated intake of addictive substances.

Role of the giant cerebral ganglion neuron in control of defensive behavior ofHelix lucorum

Neurons participating in contraction of the ommatophore retractor ofHelix lucorum were studied by morphological and electrophysiological methods. Staining by the cobalt filling method revealed a giant cerebral ganglion neuron which sends a fiber into the motor branch of the ipsilateral optic nerve. Both spontaneous and evoked contraction of the retractor was shown to be preceded by a volley of action potentials in the giant neuron. The high-frequency volley of impulses evoked by intracellular stimulation of this neuron leads to contraction of the ipsilateral ommatophore retractor; the intensity of this contraction depends on the discharge frequency. The composition of the sensory inputs of the neuron is discussed. A conclusion is drawn on the motor function of this cerebral ganglion neuron in the escape reflex ofH. lucorum.

Comparison of the Behavior of Rats after Immobilization with Structural Changes in the Motor Cortex

Behavioral and neuronal-glial changes after emotional stress induced by discontinuous (7–8 h per day for one week) immobilization were compared in Wistar rats (n = 20). Immobilization led to increases in horizontal and vertical activity and the duration of “comfort” grooming in the open field test. Morphometric measurements demonstrated significant increases in the density of hypoxic neurons in the motor area of the right hemisphere of experimental animals as compared with measures in controls. Hypoxic changes in neurons were functional in nature. Experimental rats can be regarded as a model of the redistribution of brain functional activity with a preferential increase in the role of the left hemisphere.

Time course of the redox state potential of the cerebral cortex, developing as a reaction to implanted platinum electrodes

The time course of the redox-state potential of the brain (ROSP) of the brain was investigated in five series of chronic experiments in rabbits with different numbers of electrodes (8–12,22–25,50) implanted to the level of the dura mater, with 10–12 electrodes implanted to the level of the pia mater, and with four to eight pairs of electrodes implanted in the cortical layer to a distance of 1.5–2 mm. It was found that the ROSP undergoes a number of fluctuations in the negative and positive directions with a gradually decreasing amplitude in the course of 5–25 days following the operation, after which relatively stable negative values of the ROSP are established on the average in electrodes implanted to the level of the dura mater, and positive values in electrodes implanted to the level of the pia mater.

Correlation between pattern of synaptic effects and direction of changes in RNA content in spinal motoneurons in rats

Spinal motoneurons were activated orthodromically or antidromically with preservation of inhibitory synaptic influences (experiments on healthy rats) and after blocking these influences by tetanus toxin (experiments on rats with local tetanus). The RNA content in the cytoplasm of the α-motoneurons was measured by cytospectrophotometry in UV light. The results showed no quantitative changes in the RNA of the motoneurons during action potential generation. Meanwhile the content of neuronal RNA depends on the character of synaptic influences. The RNA content in the motoneurons rises in response to excitatory and falls in response to inhibitory synaptic action. The possible mechanisms of the observed cytochemical changes in the RNA content during synaptic excitation and inhibition of motoneurons are discussed.

The Role of the Motor Cortex in the Control of Axial and Proximal Muscles in Learning

The involvement of the motor cortex in controlling the muscles of the shoulder and scapula during formation of a new motor coordination of the head and forelimb was studied in dogs. Dogs were trained to flex the forelimb to operate a lever to raise a bowl containing food and hold it up during feeding with the head tilted towards the feeder. At the early stage of training, raising of the limb occurred with anticipatory upwards displacement of the head and, on lowering the head to the feeder, lowering of the elevated limb; this is the natural coordination of head and limb movements. The new coordination needed to obtain food – maintaining the elevated limb in a posture with the head lowered – could be achieved only as a result of learning and was critically dependent on the integrity of the motor cortex. In the natural coordination, limb elevation consistently involved the main shoulder flexors, i.e., the deltoid and teres major muscles, and inconsistently involved teres minor, infraspinatus, supraspinatus, and trapezius. In this latter group, muscles often operated in antiphase to the main shoulder flexors, i.e., were active on standing and stopped being active before limb elevation. Learned limb elevation in the posture with the lowered head involved all the muscles listed, some rearranging their initial activity to the opposite. Lesioning of the greater part of the forelimb representation in the motor cortex in trained dogs led to recovery of the natural coordination of head and limb movements and the initial muscular pattern during limb elevation. Thus, it was only with involvement of the motor cortex that the initial pattern of the activity of the phylogenetically ancient axial and proximal musculature underwent rearrangement and started to operate in a new way.

Correlation between the Activities of Sensorimotor and Visual Cortex Neurons during Formation of a Cryptic Focus of Excitation (a defensive dominant) in the Cortical Representation of the Forelimb in Rabbits

Cross-correlation analysis was used to study the interaction of neurons in the sensorimotor and visual areas of the cortex in rabbits with cryptic foci of excitation formed in the representation area of the forelimb; the role of sensorimotor cortex neurons responding to light in this interaction was also studied. The results showed that in rabbits with cryptic foci of excitation, sensorimotor cortex neurons responding to light stimuli showed correlational relationships with cells in the visual cortex significantly more frequently than neurons not responding to light, while visual cortex neurons significantly more frequently formed correlational relationships with sensorimotor cortex neurons not responding to the stimulus.

Analysis of the influence of Piyavit®—a biologically active compound of natural origin—on conditioned memory, on neuron-glia interactions of hippocampus, and on neocortex of rat brain

Mnemotropic effect of Piyavit®-a biologically active compound of natural origin—was studied on conditioned avoidance in rats. Morphological changes in neocortex and hippocampus (neuron-glia complex and brain capillaries) were significant and oppositely oriented. We assume that the improvement of rats’ memory under the Piyavitis associated with metabolic changes in the nervous tissues.

Role of the motor cortex in the rearrangement of a natural movement coordination in dogs

Chronic experiments on dogs were performed to study the activity of the shoulder muscles involved in elevating the forelimb used by the animal to lift a food-containing cup and keep it elevated during eating. At the early stage of acquisition of this operant reaction, limb-lifting occurred with an anticipatory upward head movement; lowering of the head to the feeder was associated with lowering of the lifted limb. The new coordination required for food to be obtained, i.e., maintaining the elevated limb in a posture with the head lowered, could only be achieved as a result of learning. In untrained dogs with the natural coordination, elevation of the limb occurred with activation of the deltoid and teres major muscles, teres minor being active on standing but ceasing its activity before limb elevation. During training the activity of the teres minor muscle changed to the opposite pattern. Limb elevation in the learned coordination was accompanied by activation of all three shoulder flexors. Lesioning of the motor cortex in the projection area of the “working” limb, but not in other areas, led to impairments of the acquired coordination and a new pattern of shoulder muscle activity. These data led to the conclusion that rearrangement of the initial coordination was linked with the formation of a new means of elevating the limb in which the muscle pattern was supported by the motor cortex.