Effect of a vasopressin analog on the chemoreactive properties of sensorimotor cortex neurons

Subcutaneous injection of 10 micrograms desglycilargininvasopressin (DG-AVP) does not alter the mean frequency of background unit activity of sensorimotor cortical neurons. However, the pattern of impulse activity is essentially changed. At the same time the reactions of sensorimotor cortical neurons to microiontophoretic administration of acetylcholine and noradrenaline experience definite changes. It is suggested that the DG-AVP-induced changes in chemoreactive properties of neurons underlie the effect of this peptide on the learning and memory.     

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.     

Participation of beta-endorphin in the regulation of the membrane chemoreactive properties of the cortical neurons in rats

The subcutaneous administration of beta-endorphin and its endogenic accumulation in the process of elaboration of adaptation to the short-term stress influences is accompanied by the change of chemoreactive properties of rat sensorimotor cortex neurons expressed in increasing of the share of areactive cells and lowering of the share of cells reacting by the response activational form to acetylcholine and noradrenaline led to them microiontophoretically. The reaction intensity of cells, both activational and inhibitory forms to the led neurotransmitters in both experimental groups is significantly lower than in control. The revealed changes of chemoreactive properties of neurons, arising under the influence of the increase of beta-endorphin amount in brain may be one of the mechanisms of its participation in the processes of learning and memory.     

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.     

Effect of acupuncture on the catecholamine content in the hypothalamus and brain stem of rats with an experimental stomach ulcer

Significant increase of dopamine (DA) in hypothalamus and epinephrine (E) in the brain stem were revealed in the experiment on rats with experimental gastric ulcer (EGU). An acupuncture (AP) session produces a prominent increase in DOPA and especially DA in hypothalamus of the rat with EGU. Under the same conditions A, DOPA and DA in the brain stem increased as compared to the control. It is assumed that acupuncture produces a correcting effect on the reconstructive processes of catecholaminergic systems of the brain occurring in visceral pathology.     

Changes in the catecholamine content of brain structures in rats subjected to immobilization stress

The changes in DOPA and catecholamine (adrenaline, noradrenaline, dopamine) levels were investigated in noradrenaline- and dopamine-synthesizing brain nuclei of Wistar rats after prolonged immobilization stress on catecholamine analyzer (BAS, USA) using HPLC technique. Distinct DOPA and catecholamine changes were observed in locus ceruleus + nucleus subceruleus (1. c + n. sc) and substantia nigra at any stage after immobilization (right after immobilization and 15 and 30 days later). The most prominent alterations in noradrenaline content were detected in 1. c + n. sc. 30 days after immobilization NA level in these nuclei was 1.5 times higher, as compared to the control one. It is suggested that the increasing noradrenaline level in 1. c + n. sc. plays a defensive role in survival of rats after immobilization stress.     

Effect of interferon-alpha on tyrosine hydroxylase and catecholamine levels in the brain of rats

We investigated the effect of interferon on tyrosine hydroxylase (TH) and catecholamine levels in the brains of 12-week-old male Wistar rats. Interferon-alpha (300,000 IU/kg/day, s.c.) was administered to rats for 7 days. Locomotor activity of interferon-alpha-treated rats was significantly lower than that of control rats. Norepinephrine and dopamine levels and TH activities in the cerebral cortex, hypothalamus and medulla oblongata of interferon-alpha-treated rats were significantly higher than those of control rats. Norepinephrine and dopamine levels and TH activities in the thalamus and hippocampus were not different between interferon-alpha treated and control rats. These results suggest that interferon-alpha-induced depression may be related to change in the catecholamine synthetic pathway in the central nervous system.     

Regional changes in catecholamine content of the pregnant uterus

High-pressure liquid chromatography with electrochemical detection was used to identify and measure catecholamines in rat, rabbit, sheep, guinea-pig and human uteri and follow changes with pregnancy. Noradrenaline was consistently the major catecholamine and pregnancy caused a regionally specific fall in its concentration which, in rat, rabbit and guinea-pig, was associated with a decline in total content. Adrenaline was undetectable (less than 10 pmol/g myometrium) in all species and at all gestational ages studied. Dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were detected at high concentrations in guinea-pig and particularly sheep uterus. In guinea-pig uterus the dopamine/DOPAC ratio fell dramatically with pregnancy, suggesting that increased quantities of dopamine were released and catabolized. The dopamine/noradrenaline ratios suggested that dopamine is stored with noradrenaline in adrenergic neurones in guinea-pig myometrium and within an additional neuronal or cellular store(s) in sheep uterus.     

Influence of the sensorimotor cortex on single neurons of the nucleus gracilis in the cat

The aim of this study was to investigate the functional role of the cortical projections to gracile nucleus. In unanesthetized cats single nuclear units projecting to the thalamus were tested for microstimulation of cortical foci (area 4) able to evoke single joint movements in contralateral hindlimb. A very significant percentage of gracile cells was influenced, very often in excitatory manner, if their receptive field was overlaying or very close to the joint controlled by a given cortical focus. Conversely, when the location of the receptive field was more distant, the percentage of responses and the incidence of excitatory effects decreased, inhibitions occurring more frequently. From a functional point of view, such an organization of the cortico-gracile control could be effective in modulating transmission of exteroceptive information from the region of the motor target (facilitation) as well as from adjacent ones (suppression). This arrangement could provide an higher resolution of afferent messages, in relation with the cortically induced movements.     

Response of sensorimotor cortex neurons to weak disturbances of the magnetic field in Wistar rats. Cytochemical study

The influence of weak disturbances (up to 300 microT) of natural magnetic field on the protein metabolism in neurons of sensomotor cortex (layers III and V) in Wistar rats upon learning in a complex maze was studied. It was found that sensomotor neurons were very sensitive to weak disturbances of magnetic field. The protein content increased, while the nucleus-cytoplasm ratio and osmotic state of neurons remained unchanged. The specificity of neuron's reaction manifested itself in a sharp increase of nucleus and cytoplasm dimensions. In associative neurons (layer III), both the nucleus and cytoplasm were involved in the response; in efferent neurons (layer V), only nuclear parameters changed. The variance coefficients of all parameters of protein metabolism in sensomotor neurons, independently of their functional properties, were much higher than in control, which resulted in a wide diversity of cytochemical response.     

Dendritic action potentials of pyramidal tract neurons in the cat sensorimotor cortex

The intracellular activity of pyramidal tract neurons was studied during electrical stimulation of ventrolateral and ventroposterolateral thalamic nuclei in acute experiments on cats immobilized by myorelaxants. Somatic action potentials were observed and spontaneous spikes were also produced by single and rhythmic stimulation of the thalamic nuclei at the rate of 8–14 Hz, by iontophoretic application of strychnine, and by intracellular depolarizing current pulses. These potentials had a relatively low and variable amplitude of 5–60 mV and are presumed to be dendritic action potentials. It is postulated that these variable potentials arise in the dendrites of pyramidal neurons with multiple zones generating such activity. No interaction was observed where somatic and dendritic action potentials occur simultaneously. The possible functional role of dendritic action potentials is discussed.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 435–443, July–August, 1986.     

Pharmacological analysis of conditioning in sensorimotor cortex neurons in a model

In awake mobile rabbits, with electrodes implanted in the medial lemniscus, midbrain tegmental reticular nucleus, and pyramidal tract, combined stimulation of two brain of two brain structures resulted in elaboration of conditional connections in sensorimotor cortex neuronal populations. The main criterion of the conditioning was the appearance of changes in the neuronal activity on omission of the second stimulus. These changes represented a complex of electrical events, some of which were similar to and others different from the evoked responses to the second stimulus. Application of atropine, sulfate, chlorpromazine hydrochloride, serotonin creatinine sulfate, and gamma-aminobutyric acid (GABA) to the cortex at the site of the recording exerted a modulating effect on the conditional neuronal activity patterns. Of the above substances, GABA and atropine had the most pronounced effect. The GABA removed the short-latency components of the conditional changes which were similar to evoked responses. The atropine abolished the long-latency changes which differed from evoked responses.     

Comparative analysis of the morphochemical changes in the visual and sensorimotor cortical neurons of rats exposed to taftsin

White rats were treated with a single administration of immunostimulator tuftsin (Thr-Lys-Pro-Arg, in the dose 300 mcg/kg b. w.). By interferometry protein content and concentration and the area of neuron cytoplasm and nucleus were assessed 15 minutes after injection, significant alterations in protein content and cellular area were detected in one type neurons of visual and sensomotor cortex. A possible interrelation is discussed between tuftsin action and the functional activity of neurons, and between the level of their protein metabolism and establishment of emotional and motor response.     

Effect of steroid aromatase inhibitors on the catecholamine content of the hypothalamus of neonatally androgenized rats

Administration of 50 micrograms of testosterone propionate to newborn female rats on the 5th day of life provoked a reliable increase in noradrenaline and dopamine concentrations in the hypothalamus of 10-day-old rats. Neonatal administration of aromatase inhibitors on the 5th and 7th days of life prevented testosterone-induced increase in catecholamine concentrations. The data obtained prove the integration of the processes of testosterone aromatization and catecholamine accumulation in androgen-dependent brain differentiation.     

Activation of glutamate ionotropic connections of sensorimotor cortex neurons during conditioning

Changes in conditioned impulse reactions of neurons in sensorimotor cortex were studied during microiontophoretic application of glutamatergic and GABA ergic agonistic and antagonistic drugs. It was shown that ionotropic glutamate receptors (AMPA and NMDA) are activated by a conditioned stimulus. Not only large pyramidal neurons of deep cortical layers but surrounding short-axon inhibitory interneurons are involved in the reaction. It was shown that the activity of pyramidal neurons is under a constant inhibitory control from surrounding interneurons. This inhibition is involved in organization of excitatory cortical responses during conditioning.     

Effect of alcoholic intoxication of female mice prior to pregnancy on the ultrastructure of neurons in the sensorimotor cortex of the progeny

Sensorimotor cortex in the offspring of female rats alcoholized in the prepregnancy period revealed signs of delayed neuronal development and dystrophic changes in the neurons especially on the 14th day after birth. In 21-day-old animals the reparative changes increased, but normalization of neuronal ultrastructure was not observed. The dystrophic changes suggest that prenatal brain hypoxia plays an important role in the pathogenesis of alcohol-induced neuronal lesions in the offspring.     

Ultrastructural changes in the neuropile of the sensorimotor cortex during long-term protein-calorie deficiency

The effect of alimentary (protein-caloric) deficiency on the brain sensomotor cortex of mice was studied during their postnatal development. It was found that malnutrition of mice from day 10 to day 40 of postnatal period brought about the most remarkable changes in synaptic junctions located on the dendritic spines. They manifested destruction of the spine apparatus, reduction of the width of synaptic slits and of postsynaptic membranes. Dystrophic and destructive alterations are frequently encountered in dendrites, axon terminals, and myelinized axons, indicating the reduced compensatory functions of the CNS.     

Role of cortical inhibition in heterosensory interaction of neurons of the cat sensorimotor cortex

Background and evoked neuronal activity in the cat sensorimotor cortex was recorded under a-chloralose anesthesia. Pairs of heterogeneous stimuli were applied, spaced at intervals of 0, 100, 200, 300, and 400 msec. A clicking sound, flashing light, and electroshock to the contralateral forepaw were used as stimuli. Partial or complete blockade of response to test stimuli presentations spaced 100–200 msec apart were observed when using stimulation of varying modality. The greatest test response was recorded at interstimulus intervals of 200–300 msec. Intracellular mechanisms of heterosensory interaction were investigated by applying the inhibitory transmitter antagonist picrotoxin microiontophoretically to the test cell to produce local attenuation of inhibitory effects. This substance also reduced the duration of blockage following the conditioning stimulus and the occurrence of peak level test response at a lower interstimulus interval than in the controls. Either a consistent increase in the number of spikes per response at one of the interstimulus intervals or a uniform reinforcement in unit response to several different interstimulus intervals were observed in a proportion of the cells. The contribution of intracortical inhibitory influences to the mechanisms of heterosensory interaction on neurons of the cat sensorimotor cortex is discussed in the light of our findings.A. A. Ukhtomskii Institute of Physiology, A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 147–156, March–April, 1987.