Age-related dynamics of thalamic-cortical evoked potentials in the rabbit in the early period of life

Data have been obtained on development of evoked potentials in the sensorimotor cortex to electrical stimulation of the thalamic ventroposterolateral nucleus (VPL) in rabbits in early ontogeny. In 3-5 days rabbits, under four times increase of threshold electric stimulation of VPL the thalamocortical response (TCR) is presented by a positive-negative potential with a long latency and minimum amplitude parameters. Second and third TCR positive components to increasing of threshold value of electric stimulation 4 times, are differentiated from 7-8 days age. Age dynamics of TCR amplitude-temporal parameters is characterized by a shortening of latency and an increase of oscillations amplitude, most expressed at 2-3 weeks of postnatal life. TCR of one month rabbit to increased threshold electrical stimulation of VPL is presented by short-latency positive-negative oscillation with a positive phase consisting of three components with successively increasing amplitudes.     

Morphometric and electrophysiologic research on the parafascicular complex of the thalamus in early ontogeny in the rabbit

Electrophysiological, morphometric and behavioural studies have been made on the role of parafascicular complex in regulation of nociceptive sensitivity in 45 rabbits from the 1st to the 16th day of their postnatal life. The evoked potential to nociceptive stimulation was recorded already in 1-day animals. Analysis of amplitude-temporal parameters of the EPs in acute experiments revealed a sharp increase in their positive phase at the 7-8th day of life. As it was shown in the behavioural experiments, that is just the period of maximum generalized reaction to nociceptive stimulation. It was found that to this age, the surface of neurones in the complex significantly increases, their density remaining still high. The data obtained are discussed in relation to factors which account for ontogenetic changes in electrophysiological correlates of neuronal responses in the parafascicular complex to peripheral nociceptive stimulation.     

Neurophysiological analysis of postnatal development of corticostriate connections in rabbits

Evoked potentials were recorded in the caudate nucleus of adult rabbits and young rabbits aged 2–30 days in response to stimulation of the ipsilateral motor cortex. The response of the caudate nucleus in the adult rabbit consisted of a positive-negative complex with latent period of 3–5 msec. Maximal amplitude of the response was observed in the dorsorostral region of the nucleus. As the recording electrode was inserted deeper, the amplitude of the response gradually decreased but without reversal of its polarity. Responses of the caudate nucleus to stimulation of the motor cortex were recorded as early as on the 3rd day after birth. These responses were indistinguishable in configuration from responses of the nucleus of adult rabbits. Their latent period was about 10 msec. Between the 16th and 20th day after birth the latent period of the response decreased considerably — from 9 to 5 msec, and by the 30th day of life it had reached its definitive value. With age the amplitude of the response increased but the threshold of stimulation decreased, The results indicate early functional maturation of connections of the motor cortex with the caudate nucleus and they agree with the results of morphological investigations of the structural development of the afferent systems of this nucleus.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 284–289, May–June, 1982.     

Ascending effects of the posterior portion of the hypothalamus on electrical activity of the cerebral cortex in the rabbit during postnatal ontogeny

Effects of electrostimulation of the posterior hypothalamus on the neocortical activity of non-anesthetized freely-moving rabbits in the postnatal ontogenesis was studied by means of electroencephalografic method. In rabbits of the first postnatal week the electrostimulation evoked in the neocortex mainly an activation reaction of synchronized character. From the second week of the postnatal age the electrostimulation caused in the EEG of the neocortex a desynchronization reaction. The data obtained show that the posterior hypothalamus may take part in the regulation of the state of sleep and wakefulness in rabbits from the first week of the postnatal age.     

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 11–15, March, 1985.     

Formation of plastic connections of the visual system during ontogenesis of the rabbit

Analysis of evoked potentials and unit activity in the visual cortical projection area of rabbits revealed a definite succession of forming of interneuronal connections in ontogeny. In early postnatal period, the neuronal reactions were characterized by stable responses with one excitatory phase corresponding to initially negative surface evoked potential. Similarity of reactions of neurones situated in the same vertical column was observed and explained by functioning of a system of rigid connections of the thalamic relay nuclei afferents with cortical pyramidal neurones. Beginning from the third week of postnatal life of rabbits the neuronal reactions assumed a distinctly expressed phasic character, and variability of responses was seen along the vertical line. The changes revealed correlated with formation of a system of interneurones providing a possibility of plastic neuronal interaction. A study of the influence of preliminary cortical stimulation of the associative areas showed that intercentral cooperation mediated by cortical interneurones providing a systemic analysis of visual information began to form from the third week of postnatal life and reached the definitive level at later stages of development.     

Effect of epicortical stimulation on depolarization of primary afferents in rats during early postnatal ontogenesis

Studies have been made on the parameters cord dorsum potentials (CDP) during stimulation of sensorimotor cortex in rats during first month of their postnatal life. First CDP were recorded from the 10th day, their latency being equal to about 80 msec, amplitude--65-70 microV, duration--more than 200 msec. During postnatal life of rats, the latent period decreases twice, the amplitude increases more than 3-fold, whereas the duration remains almost unchanged. These data indicate maturation of the descending pathways to the spinal cord, the increase in the propagation rate along these pathways and formation of segmentary mechanisms responsible for the generation of CDP. The effect of stimulation of the sensorimotor cortex on depolarization of primary afferent was also investigated. It was found that from the 2nd week of postnatal, life, formation of supraspinal control of afferent impulsation takes place.     

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.     

Development of the caudate nucleus of rats in postnatal ontogenesis and formation of cholinergic mediation in it]

Morphological maturation of the rat's caudate nucleus and formation of cholinergic system in it were studied in postnatal ontogenesis. Under investigation were newborn rats, 7, 14, 21 day old rats and adult animals. The growth and maturation of the caudate nucleys were most intesne during the first two postnatal weeks, it was somewhat descreased by the beginning of the third week and continued in later terms as well. The structure of dendrites and axons became complicated during the first two weeks, the axo-dendritic contacts being also formed. The neuron structure in 14 days old rats was similar to that of adult animals. The activity of acetylcholinesterase in the caudate nucleus of 7 and 14 days rats was not great. It sharply increased by the 17th day and reached the level of adults with 3 weeks after birth. Possible correlations of the morpho-chemical maturation of the caudate nucleus and formation of motor activity in rats is discussed.     

Role of the monoaminergic system in the transmission of the effect of androgens on neurons of separate limbic structures of the rat brain

By means of the histochemical method intensity of monoamines fluorescence has been studied in 3-, 5-, 7-, 10-, 20-, 30- and 60-day-old intact and neonatally androgenized female rats. The neonatal androgenization increases fluorescent intensity of monoamines in the neuropil of the adjoining nucleus of the septum, of the nucleus in the terminal stripe bed and the caudate nucleus. This is especially evident on the 3d, 7th and 30th days. On the 5th day of the postnatal life the difference in fluorescent intensity of monoamines in the brain of control and test animals is statistically insignificant. Possible mechanisms responsible for the fluorescent intensity of monoamines and the role of the latter in transmitting the sex hormones effect to the neurons of the forebrain structures investigated are discussed.     

Age-related expression patterns of the CD15 epitope in the human lateral geniculate nucleus (LGN)

Summary The age-related distribution of the trisaccharide epitope 3-fucosyl-N-acetyl-lactosamine (CD15) was evaluated in the human lateral geniculate nucleus (LGN). Coronal paraffin sections from individuals between the 12th week of gestation to 99 years of age were processed for immunohistochemistry using monoclonal antibodies against the CD15 epitope. CD15 immunoreactivity was present in the neuropil from the 14th week of gestation with a graded pattern along the anteroposterior and mediolateral axes of the LGN. Immunoreactivity then became preferentially located within the future cell layers, shortly before cellular segregation was visible in Cresyl Violet stained sections. Maximal CD15 expression occurred from the 22nd week of gestation until the beginning of visual experience (second week of postnatal life). During the subsequent period the spatial pattern of CD15 expression changed. Whereas immunoreactivity in the cell layers gradually disappeared, CD15 positive astrocytes became transiently concentrated in the intercellular layers. The staining within the interlaminar region was best developed at about one year of postnatal life. The adult pattern was found at around 10 years of age, when the LGN appeared almost unstained. Two stages of CD15 expression can thus be separated. The first is characterized by neuropil staining and is synchronized with the time profile of neuronal maturation and of formation of non-stabilized contacts. CD15 is at this time possibly correlated with structural instability and increased vulnerability but at the same time with a high degree of plasticity. The second, peri- and postnatal stage is characterized by CD15 positive astrocytes. These appeared when CD15 in the neuropil disappeared. This loss of CD15 expression in the neuropil occurs during the phase of experience-dependent establishment of the mature interconnectivity and probably heralds loss in plasticity. The time-related expression pattern of CD15 is therefore compatible with the idea that CD15 levels reflect different degrees of developmental determination of retino-geniculate interaction.     

Frequency potentiation in the neonatal rabbit hippocampus

The formation of properties of frequency potentiation in the entorhinal afferent pathway of the hippocampus was studied in unanesthetized rabbits aged from 1 to 15 days. In areas CA₁ and CA₃ of the dorsal hippocampus in newborn rabbits repetitive (1–20 Hz) electrical stimulation of the perforant path led to an increase in amplitude of the slow wave of the field potential by 20–100% compared with the control and to an increase in the probability of response discharges from the neurons from 0–0.5 in the control to 0.8–1.0 during tetanization. In rabbits aged 2–3 days potentiation was more marked at a frequency of 4–6 Hz, whereas depression of the responses developed rapidly to a higher frequency of stimulation. The frequency optimum of 4–15 Hz was established on the 5th day. Potentiation of the first component of the field potential was observed starting from the 8th–10th day of life. The experimental results show that the property of frequency potentiation in the cortical afferent connections of the hippocampus is found in rabbits actually at birth, and it acquires the adult form at the beginning of the second week of life.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 6, pp. 533–539, November–December, 1979.     

Electrical activity of thalamocortical association systems in postnatal ontogeny of the cat

Electrical responses to somatic, photic, and acoustic stimulation in the sensomotor, parietal, temporal, and occipital regions of the cortex were studied in the nucleus lateralis posterior and nucleus ventralis lateralis of the thalamus by recording averaged evoked potentials in kittens (aged 3 to 41 days) anesthetized with pentobarbital. A definite order of maturation of afferent inputs into cortical association areas was demonstrated. The parietal cortex was shown to become polysensory before the sensorimotor cortex. It is suggested that the nucleus lateralis posterior is the main thalamic nucleus responsible for conduction of visual information to the cortex in kittens during the first month of life. Incorporation of this nucleus into the system conducting somatic impulsation to the sensorimotor cortex takes place by the age of 3 weeks.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 14, No. 5, pp. 476–482, September–October, 1982.     

Postnatal development of the scratch reflex in rabbits]

The development of the scratch reflex was studied in newborn (up to 2 months old) rabbits in norm and after elimination or activation of some parts of their nervous system (reticular formation, cerebellum, caudate nucleus, cerebral cortex, superior cervical sympathetic ganglia). The experiments with the section of the brain stem at the border between the medulla and the midbrain showed that in very young (5-10 days old) rabbits in norm the scratch reflex is controlled by the spinal cord with no influences of structures situated above the section's level. Later on the spinal mechanism of the scratch reflex becomes subject to supraspinal influences, among which in 2-3 weeks old animals facilitatory effects are predominant produced, in particular, by the reticular formation and the cerebellum, whereas in older age prevail inhibitory influences of the cerebral cortex, cerebellum, caudate nucleus and the sympathetic nervous system.     

Role of the caudate nucleus in the development of evoked synchronized activity

Synchronized activity (spindles, augmentation response) evoked by stimulation of thalamic nonspecific, association, and specific nuclei was investigated in chronic experiments on 11 cats before and after successive destruction of the caudate nuclei. After destruction of the caudate nuclei the duration of spindle activity in the frontal cortex and subcortical formations (thalamic nuclei, globus pallidus, putamen) was reduced to only three or four oscillations. In the subcortical nuclei its amplitude fell significantly (by 50±10%); in the cortex the decrease in amplitude was smaller and in some cases was not significant. Different changes were observed in the amplitude of the augmentation response, depending on where it was recorded. In the subcortical formations it was considerably and persistently reduced (by 50±10%); in the cortex these changes were unstable in character. Unilateral destruction of the caudate nucleus inhibited synchronized activity evoked by stimulation of the thalamic nuclei on the side of the operation only. Destruction of the basal ganglia (caudate nucleus, globus pallidus, entopeduncular nucleus, and putamen) did not prevent the appearance of synchronized activity; just as after isolated destruction of the caudate nucleus, after this operation synchronized activity was simply reduced in duration and amplitude. It is suggested that the caudate nucleus exerts an ipsilateral facilitatory influence on the nonspecific system of the thalamus during the development of evoked synchronized activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 239–248, May–June, 1977.     

Fronto-striate relationships in primate ontogeny]

A comparative investigation on the development of fields in the brain cortical frontal area and in the caudate nucleus was performed in pre- and postnatal life of the monkey and the man. Cyto- and myeloarchitectonics and quantitative methods were applied. Volumes of fields 8, 9, 10, 11, 12, 47, complex of fields 44+45+56 and the caudate nucleus were measured, the size of neuronal bodies was determined. A definite connection in the development of the caudate nucleus and the fields of the frontal area was stated. The development of these formations was found to proceed unevenly: to a definite period, the development of the caudate nucleus dominates (in Macacus ontogenesis--up to a half--one year of life, in human ontogenesis--up to 2-4 years of life). Then the development of the caudate nucleus becomes slower comparing that of the frontal fields.     

Developmental changes in threshold, conduction velocity, and depressive action of lignocaine on dorsal root potentials from neonatal rats are associated with maturation of myelination

Conduction velocity of primary afferent fibres and blocking actions of local anaesthetics seem to be developmentally regulated. The current work investigated physiological (threshold, conduction velocity, and myelination) and pharmacological (lignocaine (0.0625 to 2 mmol/L) and capsaicin (2 micromol/L)) ontogenic changes on in vitro sciatic nerve-dorsal root preparations from 0- to 12-day-old rats. As rats aged, stimulus intensities necessary to evoke A-fibre thresholds significantly decreased and A-fibre conduction velocities significantly increased. For C-fibres, thresholds significantly increased and conduction velocities significantly varied with age. The blocking potency of lignocaine varied with age: A-fibres from 4-day-old rats and younger were significantly more resistant than those from older rats, and C-fibres were blocked more uniformly amongst ages. Capsaicin significantly depressed C-fibres irrespective of age, and A-fibres were significantly reduced during the first postnatal week only. Myelination significantly increased as rats aged. A-fibre physiological parameters were significantly correlated with both other A-fibre physiological and pharmacological parameters, but C-fibre parameters were not. Peripheral A-fibre transduction mechanisms seem to require time to acquire their full stimulus-response sensitivity, which coincides with development of myelination. In contrast, peripheral C-fibres seem to have mature transduction mechanisms from the first days of postnatal life.     

Analysis of the morphological substrate of information processing in the striatum based on organizational characteristics of its afferent projections

By the method of axonal transport of the retrograde markers, the afferent projections, coming from functionally different cortical and subcortical structures to various segments of the caudate nucleus, were investigated in the putamen and the nucleus accumbens of the dog brain. On the basis of the determined peculiarities of the spatail organization of these projections, the morphological aspects of the segregated and convergent conducting and processing of the information in the striatum, which underlie their functioning, were analyzed.     

Effect of para-chlorophenylalanine and 5-hydroxytryptophan on the caudate nucleus in cats]

In unrestrained cats parachlorophenylalanine, an inhibitor of serotonin synthesis, increased the thresholds of the contraversive reaction and arrest reaction accompanied by spindle-waves in the sensory-motor cortex in the stimulation of the rostro-ventral areas of the caudate nucleus. The reactions evoked from the dorso-medial areas of the head and the body of the nucleus changed differently. On the contrary, 5-hydroxytryptophane, serotonin precursor, increased most of the indices of the caudate activity independently of the site of stimulation. It is suggested that the serotoninergic mechanisms (antagonistic to the dophaminergic system) existing in the ventral part of the caudate nucleus may trigger some caudate functions.     

Dose-dependent tazepam modulation of amplitude-temporal characteristics of thalamocortical responses and the constant potential of the sensorimotor cortex in rabbits at eye opening

The pronounced benzodiazepine (antiphobic) modulation of the amplitude-temporal parameters of different components of the thalamocortical responses (TCR) of the sensorimotor cortex is observed in rabbits in their early postnatal ontogeny. This modulation is of a dose-dependent character and is registered not after the injection of tazepam in a concentration of the "therapeutic tranquilizing window" but also in the psychotoxic plasma range. A gradual increase in blood tazepam concentration in a young rabbit pup is accompanied by the wave-like and differential decrease in the amplitude of the second and third positive (P2 and P3) and third negative (N3) TCR components, while the second negative (N2) and fourth positive (P4) components tend to a wave-like increase. The dose-dependent dynamics of tazepam modulation of the P2, P3, and N3 latencies is characterized by a wave-like and differential increase. The latency of P4 decreases slightly and that of the N2 increases with a low degree of significance. The selective dynamics of benzodiazepine modulation appears to be related with peculiarities of the electrogenesis of each of the components. The dose-dependent modulation of the level of cortical DC potential is of the same character as the respective amplitude changes in P2, P3, and N3, but its fluctiatuons are more pronounced.