Analysis of the layer distribution of transcallosal responses in the sensorimotor cortex of kittens in the 1st month of life

In experiments on 23 kittens ageing between 1-30 days, anaesthetized by barbiturate and immobilized by diplacine, studies have been made on the distribution of transcallosal responses (TCRs) along the whole diameter of the sensorimotor cortex. In order to obtain more accurate data on localization of the sources and drains of extracellular current vertical component, a method of double graphic differentiation was used. It was shown that in 1-2-day kittens TCRs have a positive oscillation form throughout all the depth of recording. During the 1st week, TCRs from the cortical surface acquired a positive-negative configuration, remaining mostly positive in deeper layers. At this ontogenetic stage, the drain of positive-negative oscillation is focused in the layer I. In 2-3-week kittens, positive-negative potentials on the surface were transformed into negative-positive responses in deep layers. The drains of this deep negative component were localized in the layers III and V-VI. On the 4th week, positive-negative TCRs on the surface changed into negative-positive potentials at various depths depending on the spatial position of the recording point. The drain of deep-laid negative component in the focus of maximum activity was found in the layer V, out of its boundaries--in the layers II-III. Ontogenetic dynamics was revealed of current drains localization of both TCRs components in the sensorimotor cortex in new-born kittens.     

The ontogeny of spontaneous skin potential responses in kittens

The evolution of frequency and amplitude of spontaneous skin potential responses (SPRs) was studied in kittens from birth to 30 days. Results showed that: i) at birth, electrodermal activity is very low, and significantly lower than in adults; ii) the evolution of electrodermal activity is rapid, the adult level being reached by the end of the third week. Frequency and amplitude evolve at approximately the same rate; iii) SPRs recorded on the forepaw were significantly more frequent and larger than those for the hindpaw up to 13 days; iv) changes in electrodermal activity as a function of sleep and waking showed that sleep is characterized by a moderate decrease of SPR amplitude and by a pronounced decrease in SPR frequency. The results are discussed in terms of maturation of the central nervous system.     

Asymmetry of the transcallosal responses in the parietal cortex of kittens in the 1st month of life

In acute experiments on kittens the process of formation of asymmetry of transcallosal responses (TCR) was studied in multiple leads from symmetrical points of the parietal cortex. By the early positive-negative TCR complex, vanishing as a result of callosotomy, predominance of positive components in the right hemisphere was found in 2-7 days kittens, whereas in 8-24 days animals the left hemisphere dominated by both phases of responses. By the late TCR component preserved after section of the callosal body, left-hemispheric asymmetry was found in the elder group of kittens; it was absent in the younger animals. TCR asymmetry in the parietal cortex depended on the sex of the animals. With their age its inversion and enhancement took place. This process is based on the increase of TCR amplitude in the left hemisphere, with no increase in the right hemisphere.     

Sexual differences in the interhemispheric asymmetry of the transcallosal responses of the associative areas in the cat neocortex

Sex differences of hemisphere asymmetry of homo- and heterotopic transcallosal responses in association cortex of 48 cats (24 male and 24 female) immobilized by tubocurarine have been studied by means of topographic EPs recordings in both hemispheres. In males left hemisphere dominates by the amplitude of homotopic and positive wave of heterotopic EPs and right hemisphere dominates by the amplitude of negative wave of heterotopic sensorimotor cortex EPs. The individual asymmetry of EPs has been observed in sensomotor cortex of females and in parietal cortex of animals of both sex. The interhemispheric asymmetry is expressed distinctly in females than in males. It is concluded that sex dimorphism is present in functional organization of associative system of (callosal and intracortical) connections in cat's neocortex projection and association areas which means its more expressed hemisphere lateralization in males with more expressed interhemispheric asymmetry of functional transcallosal connections in females.     

A layer-by-layer analysis of the components of the thalamocortical responses of the rabbit sensorimotor cortex in ontogeny]

The data obtained in the paper showed that complex dynamics of changes of spatial-temporary situation of heterocomponent thalamocortical responses (TCR) at passing the sensorimotor cortex (SMC) was conditioned by the properties of electrogenesis of each TCR component, age and frequency of stimulation of ventroposterolateral (VPL) thalamus nucleus transformation of electric profile of the second positive component (PC-2) of the TCR at passing SMC might testify to algebraic summation in this component of bioelectric processes of several generation sources (invertible and non-invertible PC-2). The revealed properties of ontogenetic dynamics of the bioelectric fields profiles of the third negative component (NC-3) of the TCR might be the consequence of the age stages of the development and change of embryonal mechanisms of electrogenesis of the definitive ones in extremely similar negativities.     

Modulation of the thalamocortical responses of the sensorimotor cortex during stimulation of the lateral hypothalamus in rabbits in ontogeny

It has been demonstrated that rhythmic stimulation of the relay thalamic nucleus in rabbits at the second half of the first month of postnatal life does not significantly affect the amplitude of the second and third positive components (PC-2 and PC-3) of the positive phase of the thalamocortical responses. Combination of rhythmic stimulation of this nucleus and that of lateral hypothalamic structures is accompanied by a significant increase of the amplitude of both positive components of the thalamocortical responses, the degree of potentiation of PC-3 being higher than that of PC-2. The described potentiation is most evident at the third week of postnatal development of rabbits.     

Role of intracortical inhibition in forming homo- and heterosensory interaction in sensorimotor cortex neurons in kittens

Homo- and heterosensory interaction were investigated in sensorimotor cortex neurons before and after picrotoxin application to anesthetized and immobilized kittens belonging to three age groups (12–30 days, 31–47 days, and 2–4 months old). Only slight inhibition of response to presentation of a second stimulus was observed in a small proportion of cells in the youngest age group at test intervals of 100, 200, and 300 msec. Picrotoxin application only produced the effect of raised background activity. Numbers of neurons with partially or fully inhibited response to test stimuli (especially spaced at 100 msec intervals) rose in the middle and older age groups. The dynamics of heterosensory interaction and how this is affected by picrotoxin application gradually approximated to that observed with adult animals. The subject of the development of inhibitory mechanisms and how they contribute to the organization of homo- and heterosensory interaction during early postnatal ontogenesis is considered in the light of the results obtained.A. A. Ukhtomsii Institute of Physiology, Leningrad. A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 234–243, March–April, 1988.     

Ontogenesis of the asymmetry of transcallosal responses in the cat parietal cortex

In acute experiments on 2-24 days old immobilized kittens and adult cats, studies have been made on the development of functional interhemispheric asymmetry of homotopical transcallosal responses in the parietal cortex. It was found that the number of animals with evident asymmetry increases with age. Alongside, with respect to such characters as asymmetry coefficient, mean amplitude of components of transcallosal components and the ratio of zones of direct and inverse domination, the increase in functional interhemispheric asymmetry was observed during the second week of postnatal life of kittens, which was accompanied by the inversion of its sign; in adult cats, the decrease in the asymmetry up to its complete absence was found. The data obtained are discussed with respect to peculiarities of the development and functional properties of the associative parietal cortex in cats.     

Effect of electric stimulation of the locus coeruleus on transcallosal response in parietal associative cortex of the cat brain

The influence of conditioning locus coeruleus (LC) stimulation on various components of transcallosal field response was investigated in the parietal cortex of the cat brain. Conditioning LC simulation caused a decrease in fast positive wave amplitude and facilitated slow negative wave. It is concluded that LC suppresses excitatory and facilitates inhibitor processes evoked in the parietal cortex by transcallosal stimulation.     

The development of neuroendocrine regulation in ontogeny

Published and author's data on hypothalamic control over the most important endocrine functions during mammalian ontogenesis were reviewed. The data presented indicates that adenohypophyseotropic protein neurohormones are synthesized and accumulated in hypothalamus long before birth. At the end of the prenatal period most of hypothalamic neurohormones reached the adenohypophysis and were involved in regulation of the tropic hormones secretion. Exceptionally, regulative properties of thyroliberin and somatostatin are only manifested in immature-born animals (rats) in early postnatal period.     

Influence of the temporal distribution of electric pulses on transcallosal single unit responses

We examined how differently timed stimuli to one auditory cortex affect the spike trains they drive in the controlateral homotopic field of anesthetized rats. Bipolar electrical stimulations consisted of trains of pulses (100 micro s, <500 micro A) at rates of 25, 50 or 125 pulses/s and with different stimulus patterns (i.e., dispersions, sequences), called "pacemaker", "accelerando" or "decelerando". Trains lasted for 342 ms and were separated by 4 s. When trains were evaluated over times comparable to the stimulus duration changes characteristically involved an initial slowing followed by recovery and several discharges both stimulus- and neuron-dependent. When evaluated by cross-correlations between cortical cell pairs, the changes extended far beyond the stimulus end. Results suggest that interhemispheric projections, by way of their averages and patterns, play key, long duration roles in the spike-dependent properties of cortical synapses (e.g., potentiation, depression) and thus of cortical circuit operations.     

A quantitative electron-microscopical study of the postnatal development of the lateral geniculate nucleus in normal kittens and in kittens with eyelid suture

The postnatal development of the lateral geniculate nucleus has been studied quantitatively with the electron microscope in normal kittens and in kittens with eyelid closure. The maturation of the synaptic organization of glomeruli in the normal kitten occurs during the period of susceptibility to eyelid closure and is due predominantly to a logarithmic increase in the number of symmetric presynaptic dendritic synapses. In contrast, the proportion of symmetric synapses falls with age in non-glomerular neuropil over this period. Unilateral and bilateral eyelid suture do not interfere with the normal development of the lateral geniculate nucleus.     

Avoidance conditioning and morphometric characteristics of the sensorimotor cortex of rats exposed to social deprivation in early ontogeny

Male Wistar rats were exposed to social deprivation in the period from the 22nd to 70th days of postnatal development. The characteristics of the learning of these rats at the age 110-120 days in the passive avoidance box and during training for active avoidance of electroshock were significant lower than those of control animals. Features of motor activities of the "isolants" in learning and testing, and in the "open field" may be related to their higher anxiety level. Morfometric studies of neurons and glial cells and neocortex thickness showed that significantly lower density of neural elements may be the result of the afferent sensory input limitation produced by the social deprivation.     

Early ontogeny of walleye,Stizostedion vitreum,with steps of saltatory development

Synopsis Frequent in vivo observations of arbitrary stages revealed a saltatory pattern of development in the early ontogeny of fluvial spawning walleye. The requirement for an environment rich in dissolved oxygen was indicated by i) spawning site characteristics, ii) the lack of carotenoid pigments, iii) swim-up at hatching, iv) a planktonic (pelagic) existence by means of immobile surface suspension and subsequent surface swimming, and v) a poorly developed temporary embryonic respiratory system, including a subintestinal-vitelline vein, hepatic-vitelline vein and duct of Cuvier. Between the start of hatching and development of the ability to remain planktonic, the temporary embryonic respiratory system was enhanced by an increase in the proportion of the total blood volume passing through the subintestinal-vitelline vein — the largest respiratory surface. Immobile surface suspension was possible due to both the buoyancy of the large oil globule and the forces of surface tension. Also, immobile surface suspension would provide low energy transport from the fluvial spawning grounds to the lacustrine environment where zooplanktonic prey would be relatively more abundant. An intimate relationship between oil globule size (shape) and a dynamic behavioral transition (including the consumption of larger particles, cannibalism, and swimbladder inflation) suggested that energy expenditures occurring during fluvial transport were necessary for appropriate developmental synchrony.     

Functional development of chemosensory systems in the fish ontogeny

Regularities of the functional development of chemosensory systems in the ontogeny of fish has been studied, i.e., the olfactory system, the taste system, and the common chemical sense. The olfactory system begins to function and provides response of juveniles to chemical signals before the taste system. Embryos that have hatched from eggs but that do not yet take food exhibit nonspecialized motor responses to olfactory stimuli already. Immediately after the transition to exogenous feeding, olfactory sensitivity to signals which elicit defensive and feeding behavioral responses begins to form and the ability to differentiate between similar odors develops. The reception of a limited number of taste stimuli occurs in the larvae during the transition to exogenous feeding. With age, the spectrum of effective taste substances expands and the time spent on the definition of palatability by juvenile fishes reduces. Functional development of individual components of the taste system arises heterochronously, i.e., the external (extraoral) form of taste reception arises earlier and more rapidly, and the oral (intraoral) form of taste reception arises slower. No information is available about the functional development of the common chemical sense in the ontogeny of fish. It is assumed that the function of the chemosensory system arises in fish in early larval stages.     

Immunoregulation in the rat: ontogeny of B cell responses to types 1, 2, and T-dependent antigens

The development of rat B cells has been examined in neonatal and adult Fischer rats through the use of type 1 (TNP-Brucella abortus), type 2 (TNP-LPS(Ph), TNP-Ficoll) and T cell-dependent (TD) (SRBC) antigens. In vivo splenic PFC responses to TNP-Brucella abortus could be induced in newborn rats and by 12 days of age had reached adult levels. In contrast, the responses to the type 2 and TD antigens were 30% and 70%, respectively, of the adult levels at 30 days of age. Adoptive transfer of the B cells from neonatal and young rats into irradiated adult hosts demonstrated that the kinetics in the development of responses to these antigens (early for type 1, intermediate for TD, and late for type 2) were not due to limiting accessory cell or T cell help in immature rats. In vitro cultures of purified B cells from neonatal and adult rats were responsive to TNP-BA and TNP-LPS(Ph) but not to TNP-Ficoll and SRBC. However, the addition of spleen cell-derived Con A supernatant to the B cell cultures resulted in responses to all four antigens, which arose as a function of B cell age, with kinetics that were identical to those observed in vivo. Fluorescent staining of B cells from rats of various ages for cell surface IgM and analysis on the fluorescence-activated cell sorter (FACS) revealed that all splenic B cells from rats 4 days of age expressed a relatively high level of sIgM, and that a subpopulation that expressed a relatively low level of sIgM increased with age until it represented approximately 50% of the adult splenic B cells. Challenging Con A supernatant-supplemented cultures of FACS-prepared low sIgM+ and high sIgM+ cells revealed that B cells responsive to TNP-Ficoll were confined to the ontogenically late-arising low sIgM+ subpopulation but that B cells responsive to TNP-BA, TNP-LPS(Ph), and SRBC were present in both subpopulations.