The effect of motor training on evoked sensorimotor cortex potentials in rats during ontogenesis]

Investigation into the influence of motor training on the functional activity of the rat sensorimotor cortex in ontogenesis has shown that three to four-month training, starting at the age of four weeks, leads to a statistically significant enhancement of sensorimotor cortex activity both by latencies and recovery cycles durations. A similar six to seven-month locomotor training produces the same statistically significant results. The differences in the shifts of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity of the sensorimotor cortex is suggested in rats aged more than a month, as a result of individual experience.     

Effect of vasopressin and enkephalin analogs on the chemoreactive properties of the sensorimotor cortex neurons in rats

On immobile rats it has been shown that subcuteneous injection of two different neuropeptides causes different distribution of activating, inhibiting and areactive cells resulting from microionoforetically administrated acetylcholine and noradrenaline without altering the mean frequency of the background unit activity sensorimotor cortical neurons. At the same time the alteration in the pattern of neurons impulse activity has been revealed, which acquires the character of packet activity with a specific packet length of 2-3, 4-6, 7-10 impulses. Depending on the injected neuropeptide reliable but almost contrary effects of the packet activity alterations have been observed. These effects have been suggested to result from the alteration of the chemoreactive properties of the neuron membranes and the corresponding reorganisations of interneuron attitudes.     

The effect of opioid neuropeptides on the cholino- and adrenoreactivity of the sensorimotor cortex cells in rats

The effect of two neuropeptides, dalargine and betaendorphine, on cholino- and adrenoreactivity of sensorimotor cortex cells has been studied in immobilized rats in acute experiments. Subcutaneous administration of the peptides led to redistribution of cells according to the type of their reaction and to changes in intensity of neuronal reactions to the applied neurotransmitters. The observed changes in chemoreactive properties of cortical neurons under the influence of the neuropeptides may play a certain part in the processes of learning and memory.     

Kinetics of chymotrypsin- and papain-catalysed synthesis of [leucine]enkephalin and [methionine]enkephalin.

The proteinase-catalysed synthesis of [Leu]enkephalin and [Met]enkephalin was studied kinetically. N alpha-t-Butoxycarbonyl-amino acids and peptides or their ethyl esters served as acyl donors, and amino acid phenylhydrazides were used as acyl acceptors. Initial-velocity measurements of alpha-chymotrypsin-catalysed peptide synthesis gave rise to kinetic patterns that are compatible with a ping-pong mechanism modified by a hydrolytic branch. Initial-rate and alternative-substrate inhibition patterns for papain-controlled peptide-bond formation are consistent with a sequential ordered mechanism with the acyl donor as the obligatory first substrate. On the basis of the observed kinetic features, reaction mechanisms are proposed for chymotrypsin- and papain-catalysed peptide synthesis that inversely equal those describing the pathways of proteolysis. The respective initial-velocity expressions for bireactant systems are given, along with the numerical values of the corresponding kinetic parameters.     

Pupillary effects of leucine and methionine enkephalin in rats after intraperitoneal administration

Changes in pupil size after peripheral administration of met-enkephalin, leu-enkephalin, or morphine were studied in the rat. With a simple pupillographic technique, the pupil diameter of male, S.D. rats (250–300 g) was measured by a series of photographs taken every 60 sec for at least 45 min after the last drug injection. Morphine (8 mg/kg, SC) caused mydriasis characterized by rapid and marked fluctuations of pupil size. Mydriasis also occurred after leu-enkephalin (5 and 10 mg/kg, IP) and met-enkephalin (20 mg/kg, IP). Both peptides induced morphine-like fluctuations. When given 15 min after morphine, leu-enkephalin (5 and 10 mg/kg) increased the mydriatic effect of morphine from 172 percent of control to 224 and 272 percent, respectively. Met-enkephalin (20 mg/kg, but not 10 mg/kg) also enhanced the mydriatic response of morphine, to 244 percent of control. These interactions appear to represent simple addition rather than potentiation. The effects of both peptides were reversed by naloxone (1 mg/kg, SC), suggesting an opiate receptor interaction for the pupillary effects of the enkephalins. The rat pupil thus provides one of the few in vivo models permitting quantification of enkephalin action after parenteral administration.     

The effect of chemical damage to the adrenal cortex on its ontogenetic development]

We studied adrenal gland of rats at the age of 1 month, which underwent injections of dioxin-preparations during a week. In 1, 6, 12 days; 1, 3, 5, 5, 7, 13 months adrenal gland mass, adrenal cortex size, adrenocorticocytes number, 3B-ol-steroid dehydrogenase and succinate dehydrogenase activities of the experimental animals differed greatly from that of the control. It was found that chemical damage of the gland at an early stage changes it greatly during the following ontogenic development.     

The effect of ubiquinone-10 on the development of D-galactosamine-induced hepatitis in rats]

It has been shown that prophylactic administration of ubiquinone protects rats liver from the toxic damage by D-galactosamine both on ultrastructural and on cell levels. Ubiquinone administration prevents necrosis in hepatocytes and preserves their ability for compensatory reactions expressed in activation of protein-synthesis regulating structures in the cell. Ubiquinone decreases hyperfermentemia and hyperbilirubinemia as well as prevents the decrease in liver protein content caused by galactosamine. Ubiquinone exerts an antioxidant effect, blocking the induction of lipid peroxidation both in intact and hepatic rats.     

Reparative changes in the sensorimotor cortex of the offspring in moderate prenatal alcoholism]

Sensorimotor cortex of 21-, 30-, 60-day-old offspring given prenatally moderate alcohol (2 g/kg) manifested signs of compensatory type: double nerve and glial cells, open capillaries, nearby nerve and glial cell bodies with basal membrane of capillaries. Intracellular reparative processes in dystrophic neurons were observed: nuclear activation, hyperplasia of cytoplasmic organelles, hypertrophy of some of them. Reparative processes are more distinct in 30-day-old rat offspring In 60-day-old offspring a polymorphic pattern of cortical synapses ultrastructure was found. However, dystrophic changes of neurons and interneuronal connections still remain.     

The structural-functional organization of the auditory cortex in rats]

Using axonal transport of horseradish peroxidase and electrophysiological mapping technique, studies have been made on structural and functional organization of the auditory cortex in rats. After the injection of HRP to peripheral parts of the auditory cortex, mainly initial neurones were found in the dorsal and median parts of the geniculate body. Electrophysiological experiments revealed the localization of neurones with widespread frequency-threshold curves and high thresholds at characteristic frequency. On the basis of the data obtained, it is suggested that similar to other mammals, rats have the areas of secondary fields of the auditory cortex which surround central coniocortex.     

A conformational analysis of leucine enkephalin as a function of pH

The conformations of Leu enkephalin in aqueous solution have been investigated as a function of pH using molecular dynamics simulations. The simulations suggest the peptide backbone exists as a mixture of folded and unfolded forms (approximately 50% each) at neutral pH, but is always unfolded at low or high pH. The folded form at neutral pH possesses a 2 --> 5 hydrogen bond and a close head to tail separation. No significant intramolecular hydrogen bonding of the carbonyl oxygens was observed in either the folded or unfolded forms of the peptide. Analysis of the Gly carbonyl oxygens and terminal groups indicated that, while the conformational population distribution of Leu enkephalin did vary noticeably as a function of pH, their hydration was essentially independent of pH and in agreement with the available NMR data. Further study indicated that the unfolded state of the peptide was not random in nature and consisted of one major unfolded backbone arrangement stabilized by a persistent hydrophobic interaction between the side chains of Tyr and Leu.     

Disordered learning and sleep structure in rats with a cobalt-induced epileptogenic focus in the sensorimotor cortex

The influence of cobalt-induced epileptogenic foci in the somatosensory area of the cerebral cortex on sleep-wakefulness pattern has been studied in rats and the data obtained were compared with the learning ability of rats. It has been established that the formation of cobalt-induced epileptogenic foci may result in a decreased ability to learn that correlated with the selectivity of phasic components of the paradoxical sleep hippocampal theta-rhythm.     

Model of recovery of locomotor ability after sensorimotor cortex injury in rats

Animal models of locomotor recovery after brain injury provide tools for understanding the basic neurobiological processes that may underlie recovery after stroke in humans. Measurement of the ability of rats to traverse a narrow elevated beam has proven to be a particularly useful test of locomotor function. Repeated measurement of this behavior over time provides a simple method for quantifying the rate and degree of a rat's locomotor recovery after sensorimotor cortex injury and constitutes a tool for studying its mechanisms and possible treatment strategies. The model has proven particularly useful in predicting the effects of drugs on poststroke recovery in humans.     

The effect of pesticides on the development in rats of osteosarcomas induced by 90Sr]

In experiments with rats the authors have assessed the development of remote effects of radiation (90Sr) combined with chronic exposure to chlorophos and lindane within a wide range of doses. It has been shown that chronically administered chlorophos and lindane have no carcinogenic and cocarcinogenic effects.     

The influence of BT-melanin on the recovery of conditioned instrumental reflexes in rats surviving after ablation of the sensorimotor cortex

It has been shown the reinforcement of the corticofugal plasticity in adult rats after unilateral ablation of sensorimotor cortex accompanied by intramuscular injections of low concentrations of BT-melanin. In result the process of compensatory recovery in rats central nervous system is accelerated, confirmable by the rapid recovery of previously elaborated instrumental conditioned reflex in comparison with the control animals. It is assumed that the compensation of the motor deficit arised after the sensorimotor cortex ablation is ensured by the ability of two main motor systems of the brain (corticospinal and corticorubrospinal) to duplicate each other. This phenomenon of functional switching of descending influences has also been revealed in control group rats, not injected with BT-melanin. However the difference in time periods of operantly conditioned reflex recovery, for experimental and control groups, argues the apparent acceleration of this process, induced by the effects of BT-melanin. The obtained data considers the possibility of applied use of low concentrations of BT-melanin.     

Ultrastructure of sensorimotor cortex neurons in the progeny of rats receiving alcohol during pregnancy

Dynamics of ultrastructural changes in the sensomotor cortex neurons has been studied on the 21st, 30th and 60th days of life in offspring born by the rats given 20% alcohol (2 g/kg) during pregnancy. Moderate antenatal alcoholization produces certain disturbances in the ultrastructure of the cortical neurons and their dendrites. This is manifested as presence of retardation signs in maturation of nervous cell populations, as dystrophic changes in the neurons and their dendrites and display of reparative character with their own dynamics in the postnatal period of ontogenesis. The first two categories of the ultrastructural changes in the cortical neurons are more manifested at early stages of the postnatal development of the offspring, and the reparative processes--at the age of two months. Despite the presence of the reparative shifts, the dystrophic changes of the neurons of hypoxic character are present up to the period of sexual maturation. This demonstrates that the antenatal alcoholic intoxication in the offspring is manifested in the postnatal ontogenesis for a long time.