Cytophotometric study of the AChE-containing nerve cells and fibers of the rabbit heart after electrostimulation of the area hypothalamica posterior

By means of cytophotometry and a computer in the cardiac intramural neural plexus of 17 experimental and 17 control rabbits acetilcholine esterase (AChE) activity (revealed by Karnovsky--Roots' method) was investigated. It was stated that a prolonged electrostimulation of the area hypothalamica posterior (AHP) produced statistically significant 2-fold decrease of AChE activity in the cardiac neural cells and fibres. When the stimulation of AHP was stopped, the decreased enzymatic activity was observed for the first two weeks, then by the end of the 4th week it again reached its control level. The results of the work were discussed in view of possible disorders of regulating vegetative-trophic effects of the posterior hypothalamus on innervative and executive tissue elements of the heart.     

Preferential ipsilateral influence of the posterior hypothalamus on the neocortex

On the 10th–20th day after precollicular transection of the brain stem weak low-frequency electrical stimulation of the posterior hypothalamus preferentially activates the ipsilateral neocortex. After unilateral injury to the posterior hypothalamus, synchronous activity predominates in the ipsilateral neocortex. In premesencephalic animals weak single electrical stimulation of the posterior hypothalamus evokes the appearance of spindles in ipsilateral zones of the frontal cortex, whereas stronger single stimulation causes the diffuse generation of spindles in various parts of the neocortex. Besides this preferential unilateral effect, the influence of the posterior hypothalamus is found to be more strongly expressed in the frontal than in the occipital cortex. It is postulated that the posterior hypothalamus exerts its influence on the neocortex through the thalamic nuclei.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 139–145, March–April, 1976.     

Participation of the posterior hypothalamus in the activity of the ascending activating system]

In chronic experiments on cats with premezencaphalic section of the brain stem electrica stimulation of the posterior hypothalamus caused desynchronization of the electrical activity of the neocortex. After the isolated injury of the posterior hypothalamus a moderate electrical stimulation of the medical part of the midbrain reticular formation failed to cause any pronounced activation of the neocortex. The results obtained indicated an important role of the posterior hypothalamus in the function of the ascending activating system.     

The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes]

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.     

Effect of posterior hypothalamic stimulation on neocortical electrical activity in the chronic premesencephalic cat

Chronic experiments were carried out on 19 adult cats after preliminary division of the brain stem at the level of the anterior border of the superior colliculus. High-frequency electrical stimulation of the posterior hypothalamus of these animals caused desynchronization of electrical activity in different parts of the neocortex. The influence of the posterior hypothalamus was predominantly on activity in the frontal zones of the neocortex. It is postulated on the basis of these results that the posterior hypothalamus has an activating effect on the neocortex through the thalamic nuclei.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 47–53, January–February, 1976.     

The effect of electric stimulation of different regions of the cerebral cortex on the alimentary reaction in rabbits]

The influences of different parts of the neocortex on the rabbit alimentary behaviour produced by stimulation of the hypothalamic "alimentary centre" were studied in chronic experiments on rabbits with electrodes implanted in different formations of the limbic system and the midbrain. It has been found that electrical stimulation of the frontal and anterior parietal cortical areas raised the threshold of the evoked alimentary reaction. Inhibitory influences of the frontal areas proved to be stronger and more prolonged than those of the anterior parietal area. Electrical stimulation of the posterior parietal and occipital cortical areas decreased the threshold of the evoked alimentary reaction. Coagulation of the dorsal hippocampus eliminated the inhibitory influences of the neocortex, while coagulation of the mesencephalic reticular formation discontinued the facilitating influences of the neocortex on the alimentary reaction.     

Appearance and differentiation of NADPH-D-neurons in ontogeny of the cerebral cortex in rats

The appearance of presumptive NO-ergic nerve cells and their differentiation in the rat neocortex were studied. For this purpose, a comparative analysis of the development and differentiation of NADPH-D-positive neurons in the neocortex transplants taken from the embryos of different ages and transplanted in the occipital cortex of adult rats and in the normally developing cerebral cortex. The nervous tissue was stained histochemically for NADPH-D. The results we obtained suggest that no NADPH-D-containing neurons were found in the transplants from 15-day embryos, while they developed in those from 18-day embryos. Hence, precursors of NO-ergic neurons were still absent in the presumptive neocortex of 15-day embryos and appeared only on day 16-18 of embryogenesis. Expression of NADPH-D begins in them only within four to five days, but the neurons are differentiated during a relatively short period of time. Most NADPH-D-positive neurons reach their structural-functional maturity already by the end of the first week of postnatal development, while their complete maturation takes place by the end of the second week of postnatal development.     

Establishment of the afferent function of the striatum in the rabbit during early ontogenesis

The study is dedicated to electrophysiological analysis of development of the caudate nucleus afferent function in rabbits in early postnatal ontogenesis. By amplitude-temporal parameters of the evoked potentials (EPs) of the caudate nucleus, recorded in response to stimulation of afferent inputs from the cortical regions (motor and limbic) and substantia nigra, similar dynamics of these afferent pathways functional maturation is revealed from the beginning of functioning (in the age of 3-5 days) to the definitive level (by the 30th day of life). The most significant changes of the amplitude-temporal parameters of the evoked potential, particularly of latencies are observed during the 3d week of postnatal life. On the basis of the obtained data, the conclusion is made on the formation of a common system of striatum sensory integration in the 3d-4th week of rabbits life. This age period is considered as critical.     

Functional Analogs of the Motor and Premotor Areas of Neocortex in Developing White Rats

To study functional characteristics of the brain cortex motor areas in developing white rats and to determine their interlocation in rat pups at the different age and at critical terms of formation of motor representations in the process of postnatal development, mapping of neocortex frontal areas at the age up to 1.5 months was performed using intracortical microstimulation method. It has been shown that for first 10 days of postnatal development the microstimulation is not effective to evoke corticomotor reactions. An earlier appearance of functional activity of the non-primary motor cortex has been established, as compared with that of the primary motor cortex. It is suggested that there occurs a parallel, but heterochronous formation of primary and non-primary motor areas at the frontal neocortex territory.     

Effect of phosphatidylcholine on the body temperature and activity of posterior hypothalamus neurons in animals

The experiments on rats and rabbits have shown that exogenous phosphatidyl choline (PC) was capable of altering the body temperature and bioelectrical activity of posterior hypothalamus neurons following intravenous and intracerebroventricular administration. Intracerebroventricular PC was more effective in raising the body temperature of rats. The experiments on rabbits have demonstrated that the influence of PC (intravenous administration) on the body temperature depended on the initial body temperature. In rabbits, the changes in the impulse activity of certain non-thermosensitive posterior hypothalamus neurons induced by intracerebroventricular PC administration were found to be dependent on the initial firing rates. PC inhibited the increase in bioelectrical activity of thermosensitive neurons in posterior hypothalamus caused by the rise in the brain temperature secondary to body temperature elevation.     

Morphological studies of the matrix in human hypothalamus

The variations of matrix and ependyma in the hypothalamus was histologicaly investigated in 120 human brains of both sexes from the 13 week old fetuses up to the end of the first year of postnatal life. The plane of cuts were in the region of the anterior hypothalamic nucleus, of the ventromedial nucleus, and the arcuate nucleus. We have found that the exhaustion of the matrix begins in the 14 week old embryo in the anterior and medial hypothalamus. A subependymale zone is present in these areas in the 17 week old embryo and exists up to 23 week. The one-cell-layer ependyma appears in the anterior are of the ventromedial nucleus at first in the 24 week week old embryo. After this the ependyma appears from the 25 to the 28 week old embryo in the regions of the anterior hypothalamic nucleus and the other areas of the ventromedial nucleus. In the immediate surrounding of the arcuate nucleus we observed the first alterations in the 15 week old embryo. The exhaustion of matrix is a continuous process up to the 23rd week. The boundary of the third ventricle remained to be a multilayer and in all stages of development cells were found, which reach into the lumen. Only after birth the multilayer boundary was reduced. At the end of the first year of postnatal life the one-layer ependyma was developed at a few sites. We could not find any significant variations of matrix exhaustion in the different sexes.     

Appearance and Differentiation of NADPH-D-Neurons in Ontogeny of Cerebral Cortex in Rats

The appearance of presumptive NO-ergic nerve cells and their differentiation in the rat neocortex were studied. For this purpose, a comparative analysis of the development and differentiation of NADPH-D-positive neurons in the neocortex transplants taken from the embryos of different ages and transplanted in the occipital cortex of adult rats and in the normally developing cerebral cortex was undertaken. The nervous tissue was stained histochemically for NADPH-D. The results we obtained suggest that no NADPH-D-containing neurons were found in the transplants from 15-day embryos, while they developed in those from 18-day embryos. Hence, precursors of NO-ergic neurons were still absent in the presumptive neocortex of 15-day embryos and appeared only on day 16–18 of embryogenesis. Expression of NADPH-D begins in them only within four to five days, but the neurons are differentiated during a relatively short period of time. Most NADPH-D-positive neurons reach their structural–functional maturity already by the end of the first week of postnatal development, while their complete maturation takes place by the end of the second week of postnatal development.     

Postnatal expression of Doublecortin (Dcx) in the developing cerebellar cortex of mouse

We have investigated the expression of Doublecortin (Dcx) protein in the developing cerebellum of mouse from postnatal 2nd day to postnatal 22nd day and in young adults by immunohistochemistry. Strong expression of Dcx was present in the inner zone of the external granule cell layer, and remained strong while postmitotic granule cell precursors were present in this transitory layer. Descending granule cell precursors exhibited Dcx immunostaining not only while migrating but for a short time also after their settlement. Dcx-immunostained cells appeared in deep cerebellocortical territories and in the cerebellar white matter during the first postnatal week. These bipolar cells were arranged in the sagittal plane and built up transitory migratory streams during the second postnatal week and their number gradually decreased during the third postnatal week. Upward migration of bipolar cells was observed while leaving the migratory streams, penetrating the internal granule cell layer and the molecular layer. These cells were considered as precursors of late migrating molecular layer interneurons. However, a proportion of Dcx-immunostained cells underwent a bipolar-to-multipolar dendritic remodellation and - on the basis of strong morphological similarities - was taken for "multipotent progenitor cells", described recently in the neocortex of adult rat.     

Electrophysiological study of the functional connections of the hypothalamus with the forebrain in the tortoise Emys orbicularis

During stimulation of the posterior hypothalamus, the evoked potentials with short latent periods, high amplitude and poor exhaustion by rhythmic stimulation were recorded in the hippocampal cortex. In the piriform cortex, the evoked potentials exhibited longer latent periods and complex configuration. Less readily the evoked potentials appeared in the neocortex, their latency being very large. During stimulation of the anterior hypothalamus, maximum activity was also localized in the hippocampal cortex. The data obtained indicate close connection between hypothalamic structures and the hippocampal cortex. The latter is presumably the main projectional area for the ascending afferentation from the hypothalamus.     

Effect of sensory stimulation on the lamina V pyramidal neurons of the gyrus cinguli in the rat

Three groups of Wistar-rats were exposed to permanent noise (80 db) during different periods in their postnatal life: the first group was exposed starting from birth for a period of four weeks, the second one from birth up to nine weeks of age and the third group from the fifth up to the ninth week postnatal. A fourth group (control animals) was reared under normal laboratory conditions. After the experiments the brains were exposed to a modified GOLGI-method. In lamina-V-pyramids of the gyrus cinguli lightmicroscopical results: length, number and distribution of spines on the main apical dendrites and on the apical dendritic branches where evaluated. Main results: 1. Permanent noise during the early postnatal development phase of the brain of rats (from birth up to the fourth week of age) causes a statistically significant increase of apical spines. The spines-values are 20% above those of the control animals. 2. Permanent noise from birth up to the ninth week of age or applied only during the later postnatal period (from the fifth week up to the ninth week of age) does not significantly alterate the spines-value. 3. The results are estimated as a consequence of extreme environmental factors causing effects, comparable with an universal stress reaction. Conclusions were discussed in comparison to the results of other authors.     

Involvement of accessory neurosecretory nuclei of hypothalamus in the formation of hypothalamohypophyseal system during prenatal and postnatal development in rats

We studied the development of direct axonal connections of the accessory neurosecretory hypothalamic nuclei with the posterior pituitary lobe on the fixed rat brain from day 15 of embryogenesis until day 10 of postnatal development using the retrograde diffusion method of the lipophilic fluorescent carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate along the neuronal membranes. The marker was applied onto the posterior pituitary lobe and, after incubation in a fixative, fluorescing bodies of nerve cells were visualized in the hypothalamus. Neuronal axons of the retrochiasmatic nucleus were the first of the accessory nuclei to ingrow in the posterior pituitary lobe (on days 16-17 of embryogenesis). Neurons of the circular and dorsolateral nuclei and the nuclei of the median bundle of the forebrain sent their axons to the posterior pituitary lobe starting from the first days of postnatal development. No direct connections of the anterior commissure and perifornical accessory nuclei with the posterior pituitary lobe were found in perinatal development. These facts are discussed in the light of concepts about the different functional role of accessory peptidergic hypothalamic nuclei in rats.     

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 hypothalamic-cortical interrelations in the ontogeny of the cat

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.     

Involvement of Accessory Neurosecretory Nuclei of Hypothalamus in the Formation of Hypothalamohypohysial System during Prenatal and Postnatal Development in Rats

We studied the development of direct axonal connections of the accessory neurosecretory hypothalamic nuclei with the posterior pituitary lobe on the fixed rat brain from day 15 of embryogenesis until day 10 of postnatal development using the retrograde diffusion method of the lipophilic fluorescent carbocyanine dye 1,1"-dioctadecyl-3,3,3",3"-tetramethylindocarbocyanine perchlorate along the neuronal membranes. The marker was applied onto the posterior pituitary lobe and, after incubation in a fixative, fluorescing bodies of nerve cells were visualized in the hypothalamus. Neuronal axons of the retrochiasmatic nucleus were the first of the accessory nuclei to ingrow in the posterior pituitary lobe (on days 16–17 of embryogenesis). Neurons of the circular and dorsolateral nuclei and the nuclei of the median bundle of the forebrain sent their axons to the posterior pituitary lobe starting from the first days of postnatal development. No direct connections of the anterior commissure and perifornical accessory nuclei with the posterior pituitary lobe were found in perinatal development. These facts are discussed in the light of concepts about the different functional role of accessory peptidergic hypothalamic nuclei in rats.     

Electrophoretic characteristics of nuclear proteins in the rat liver after electric stimulation of the hypothalamus

The liver nuclear proteins of 3- and 6-month old rats were studied by the gel-electrophoresis technique after electrostimulation of hypothalamus. In this case new nuclear proteins with low molecular weight were found. The electrophoretic rate of these proteins is higher than that of histone H4. A decrease in the content of histone H2B in the nuclear liver of 6-month old rats was also found after electrostimulation of hypothalamus. The mechanism of this phenomenon is discussed.