Activity of neurons in the anterolateral region of the rabbit motor cortex during taking food and nonfood objects in instrumental behavior

We showed earlier that only 2-4% of N-neurons in the rabbit's anterolateral ("masticatory") motor cortex (AC) that are being specialized in relation to Newly formed acts (such as pressing the pedal, approaching the pedal) during the elaboration of instrumental food-acquistion behavior. The majority of neurons in this area are O-neurons that are specialized in relation to the Older acts formed long before the acquisition of instrumental behavior: mostly taking of food. It was shown also that electrical stimulation of this area produced jaw movements. It might seem reasonable to propose that the number of N-neurons may be increased in this area if pedal pressing in substituted with instrumental act like seizure and pulling a ring that is more corresponding to the "projectional property" of the AC. Here we show that the number of N-neurons in rabbit's AC remains constant -3.4%, even is the animals that were trained to pull a ring instead of pressing a pedal. Thus, we assume that the small number of N-neurons is the stable property of the AC. However, the role of the AC in the subserving of the behavior does not remain the same. Much more AC units (O-neurons) were activated in the ring pulling than in the pedal pressing instrumental act.     

Estimation of the interaction strength in the rabbit sensomotor cortex neurons before and after formation of the defense focus

The strength of interaction between neurons in the sensorimotor cortex of rabbits was compared before and after the formation of a hidden excitatory focus (dominant) in this cortical area. In control experiments the interactions between the neurons was significantly stronger in cases when the influence of the neurons with higher spike amplitude on the neurons generating lower-amplitude pulses was assessed. This difference disappeared in the dominant focus.     

Activity of anterolateral motor cortex neurons in instumental food-acquisition and alcohol-acquisition behavior

Singleunit activity of anterolateral area of motor cortex in rabbits subjected to chronic ethanol treatment was recorded to study interconnections of neuronal mechanisms of newly formed instrumental alcohol-acquisition behavior (IAB) and previously formed food-acquisition behavior (IFB). Adult animals were trained to perform IFB in experimental cage equipped with two food boxes and two pedals situated in the corners of the cage. Food was presented automatically in a food box after the pressing of an appropriate pedal. Same rabbits after 9 mo. of chronic alcohol treatment were trained to perform IAB in the same experimental cage (gelatin capsules filled with 15% ethanol solution were placed into the food box instead of food). Activity of 121 units of anterolateral area of motor cortex was studied. Each unit discharges were analysed in IAB as well as in IFB. The data obtained testifies that neuronal sets subserving IAB and IFB overlap but not completely. 44 "common" neurons permanently activated in both behaviors and 3 neurons specifically activated in each of behaviors (one in IAB and two in IFB) were found. We consider the formation of IAB as systemogenesis that is related to the consolidation processes: the formation of new neuronal specializations and to the accommodative re-consolidation: modification of early specialized cells ("common"). It is shown in the Discussion that present experiments help us not only understand interconnections of neuronal mechanisms of newly formed IAB and early formed IFB but also provide an additional insight into the nature of similarity between neuronal mechanisms of long-term memory and long-lived modifications resulting from repeated drug exposure.     

The effect of acute ethanol administration on the neuronal activity of the motor cortex of the rabbit in its food-acquisition behavior]

Units activity of anterolateral area of rabbits motor cortex, realizing instrumental food-acquisition behaviour was studied at acute injection of ethanol and in control experiments (injection of physiological solution) in order to compare possible ethanol effects on the motor area of the cortex with effects revealed by us earlier at studying the activity of the limbic cortex units in the same experimental conditions. It was shown that after ethanol injection the number of active units and the pattern of the motor cortex units specialization in contrast to the limbic one remained constant. Nevertheless, composition of the motor cortex units involved in subserving the behaviour changed because of recruitment [correction of recrutation] of one cells (from V-VI layers of the cortex) in this process and exclusion of other ones (from II-IV layers). The value of activation frequency ratio to the frequency of the background of the involved units increased.     

Responses of motor cortex neurons of the cat to auditory stimulation and their role in the instrumental food reflex

The responses of motor cortex neurons in the cat to the presentation of a single auditory click and a series of 10 clicks presented with 1,000/sec frequency were studied under conditions of chronic experiments before and after the development of an instrumental food reflex. After reflex development a single presentation of a positive conditioned stimulus (single click) markedly influenced for 7 sec the appearance of instrumental movements. At the same time, the immediate responses of motor cortex neurons to presentation of the conditioned auditory stimulus had no impact on the appearance in the motor cortex of discharges leading to the realization of instrumental movements. Consequently, motor cortex neurons do not require activation from afferent sensory inputs for the generation of such discharges. The immediate neuronal responses to conditioned stimulation did not inhibit the realization of the instrumental reflex. It is proposed that they are associated with the realization of motor function in the unconditioned defensive response evoked by the presentation of an auditory stimulus. The presence or absence of responses to auditory conditioned stimulation was dependent upon the signal meaning of the stimulus, its physical parameters, and the degree of excitability of the animal.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 539–550, July–August, 1985.     

Correlation of the rat behavior after immobilization with structural reorganization in the motor cortex

Behavioral changes and accompanying morphological neuron-glia reorganization in the rat brain were compared after emotional stress. Wistar rats (n = 20) were stressed by the interrupted immobilization, which was carried out during one week 7-8 h daily. Behavioral immobilization of rats was accompanied by an increase in horizontal and vertical locomotors activity and in duration of the III and IV phases of grooming ("comfortable" grooming) in the "open field" test. The morphometric studies showed a statistically significant increase in the density of hypoxic neurons in the right neocortex of the experimental animals as compared with control. Hypoxic changes in neurons were of functional character. Experimental rats can be considered as a model of redistribution of functional brain activity with preferential intensification of the left brain hemisphere.     

Directional tuning of visual cortex neurons in the cat before and after nembutal injection

Directional tuning was investigated in 40 neurons of the primary visual cortex (area 17) before and after Nembutal injection during acute experiments on immobilized cats. Preferred orientation (PO) in 50% of neurons was found to be stable after the drug, while the remainder showed a consistent shift in PO (averaging 53.6±8.0°) for a number of hours. Neurons with consistent PO more frequently showed a preference for horizontal and vertical stimulus orientation; cells with unstable tuning had a wider PO distribution. More refined directional detection (i.e., finer tuning) was noted in "stable" rather than in "unstable" neurons both before and after administering the drug. Under narcosis, directional tuning altered in 50% of cells — an effect more marked in "unstable" than in "stable" cells (68% as against 38%). Mean background discharge rate also fell by an average of 5.5-fold and induced firing rate declined 1.5-fold during narcosis, moreover.Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 669–676, November–December, 1991.     

Response of parietal association cortex neurons to acoustic stimulation before and after auditory cortex blockage in the cat

The effect of auditory cortex blockade on response patterns of parietal association cortex neurons responding to different frequency tones was investigated in the cat. Blockade was produced by two methods: bilateral isolation and application of a 6% Nembutal solution to the auditory cortex surface. Frequency threshold curves were plotted for all test neurons. The majority of test neurons (84%) displayed one or two characteristic frequencies before blockade, as against only 63% of all neurons responding following blockade. Changes also affect the range of frequencies at which the cells could respond. Virtually all test neurons responded to application of a broad spectrum of frequencies under normal conditions. After blockade of the auditory cortex 69% of neurons no longer responded to tones above 8–10 kHz. This would suggest that mainly information on high frequency tones is transmitted via the auditory cortex. The question of where acoustic information for parietal association cortex neurons mostly originates is also discussed; association thalamic nuclei are thought to be the main source.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 354–360, May–June, 1986.     

Structural and metabolic changes in the limbic cortex of the rabbit in response to experimentation with the hypothalamus

By means of the light and electron microscopy, histochemical and cytophotometrical methods the anterior subarea of the cerebral limbic cortex has been studied in 30 experimental and 30 control rabbits. The experimental animals have been given 3, 15 and 30 sessions (1 h per day) of electric irritation (0.05 mA, 50 Hz, 1 msec) on the posterior hypothalamic field (PHF). Twelve rabbits from 30 control animals make an intact group and 18--a group with inactive electrodes inserted into the PHF. After 3 and especially after 15 sessions it has been revealed: in neurons--an acute swelling, edematous alterations, hyperchromatosis and shrinkage, changes in lactate dehydrogenase, succinic dehydrogenase, nicotinamide-adenine-dinucleotide-diaphorase and nicotinamide-adenine-dinucleotide-phosphate-diaphorase activities, in neuroglia--hypertrophy and weakly manifested hyperplasia. After 30 sessions synapses degenerated after the dark type are revealed. More intensive structural and metabolic changes are noted in the middle cytoarchitectonical complex. The changes of the enzymatic activity are considered as certain signs of weakening mitochondrial processes, connected with energy production, increasing glycolysis, decreasing level of the energetic provision of the cytoplasmic synthesis, arising under conditions of a disturbed transneuronal influence on the cortex by the hypothalamus.     

Electrical characteristics of neurons in the cat motor cortex

Electrical characteristics of motor cortical neurons were studied in acute experiments on immobilized cats. Values of the input resistances varied from units to tens of megohms (mean 11.11±3.93 MΩ). The threshold current is a hyperbolic function of input resistance of the corresponding neurons and negative correlation was found between the axonal conduction velocity and input resistance. The time constant (τ₀) of the membrane was 7.1±3.46 msec. A time constant τ₁, of 1.65±0.36 msec, could also be distinguished in some neurons. Electrotonic lengths of dendrites of the cortical neurons were calculated by the use of Rall's model: mean 3.66±0.94 (in units of length constant).     

Increased NADH-dependent production of reactive oxygen intermediates by microsomes after chronic ethanol consumption: comparisons with NADPH.

Microsomes from chronic ethanol-fed rats were previously shown to catalyze the NADPH-dependent production of reactive oxygen intermediates at elevated rates compared to controls. Recent studies have shown that NADH can also serve as a reductant and promote the production of oxygen radicals by microsomes. The current study evaluated the influence of chronic ethanol consumption on NADH-dependent microsomal production of reactive oxygen intermediates, and compared the results with NADH to those of NADPH. Microsomal oxidation of chemical scavengers, taken as a reflection of the production of hydroxyl radical (.OH)-like species was increased about 50% with NADH as cofactor and about 100% with NADPH after chronic ethanol consumption. The potent inhibition of the production of .OH-like species by catalase suggests a precursor role for H2O2 in .OH production. Rates of NADH- and NADPH-dependent H2O2 production were increased by about 50 and 70%, respectively, after chronic ethanol consumption. A close correlation between rates of H2O2 production and generation of .OH-like species was observed for both NADH and NADPH, and increased rates of H2O2 production appear to play an important role in the elevated generation of .OH-like species after chronic ethanol treatment. Microsomal lipid peroxidation was elevated about 60% with NADH, and 120% with NADPH, after ethanol feeding. With both types of microsomal preparations, the characteristics of the NADH-dependent reactions were similar to the NADPH-dependent reactions, e.g., sensitivity to antioxidants and free radical scavengers and catalytic effectiveness of ferric complexes. However, rates with NADPH exceeded the NADH-dependent rates by 50 to 100%, and the increased production of reactive oxygen intermediates by microsomes after ethanol treatment was greater with NADPH (about twofold) than with NADH (about 50%). Oxidation of ethanol results in an increase in hepatic NADH levels and interaction of NADH, iron, and microsomes can produce potent oxidants capable of initiating lipid peroxidation and oxidizing .OH scavengers. These acute metabolic interactions produced by ethanol-derived NADH are increased, not attenuated, in microsomes from chronic ethanol-fed rats, and it is possible that such increases in NADH (and NADPH)-dependent production of reactive oxygen species play a role in the development of oxidative stress in the liver as a consequence of ethanol treatment.     

Quantitative evaluation of motor function before and after engraftment of dopaminergic neurons in a rat model of Parkinson's disease

Although gait change is considered a useful indicator of severity in animal models of Parkinson's disease, systematic and extensive gait analysis in animal models of neurological deficits is not well established. The CatWalk-assisted automated gait analysis system provides a comprehensive way to assess a number of dynamic and static gait parameters simultaneously. In this study, we used the Catwalk system to investigate changes in gait parameters in adult rats with unilateral 6-OHDA-induced lesions and the rescue effect of dopaminergic neuron transplantation on gait function. Four weeks after 6-OHDA injection, the intensity and maximal area of contact were significantly decreased in the affected paws and the swing speed significantly decreased in all four paws. The relative distance between the hind paws also increased, suggesting that animals with unilateral 6-OHDA-induced lesions required all four paws to compensate for loss of balance function. At 8 weeks post-transplantation, engrafted dopaminergic neurons expressed tyrosine hydroxylase. In addition, the intensity, contact area, and swing speed of the four limbs increased and the distance between the hind paws decreased. Partial recovery of methamphetamine-induced rotational response was also noted.