Postnatal Development of the Posterior Hypothalamic Theta Rhythm and Local Cell Discharges in Rat Brain Slices.

Theta rhythms have been recorded from rat brain slices of the posterior hypothalamic area (PHa), including the supramammillary and posterior hypothalamic nuclei. Additionally, in numerous studies theta-related neurons were identified in the PHa according to the classification of Bland and Colom (Progress in Neurobiology, 41, 157-208, 1993). It is currently widely accepted that the PHa contributes to the process of HPC theta frequency programming at least in certain behavioral states. The postnatal development of the HPC and its ability to generate theta has also been a subject of studies. Specifically, it was found that theta oscillations are present in the HPC of 8-10 days old rat pups and turn into a well-synchronized and high-amplitude activity in the following few days. In our current study, we therefore focused on the postnatal development of cholinergically-induced theta rhythm and theta-related neuronal activity in PHa slices obtained from 8 to 24 days old rat pups. Theta activity was observed in the PHa preparations at the age of 8-10 days and then progressively increased its probability of occurrence, amplitude and synchrony up to the age of 22-24 days when it reached a plateau phase. A steady increase in the number of recorded neurons correlated with local theta oscillations was also observed.

Regional distribution of benzodiazepine binding sites in the human newborn and infant hypothalamus. A quantitative autoradiographic study.

Using in vitro quantitative autoradiography and [3H]flunitrazepam we examined the rostrocaudal distribution of benzodiazepine binding sites in the human neonate/infant hypothalamus. The autoradiographic analysis shows the presence of a heterogeneous distribution throughout the rostrocaudal extent of this brain structure. High [3H]flunitrazepam binding corresponds primarily to the diagonal band of Broca and the preoptic region. The labelling in the preoptic region showed a rostrocaudal increase, contrasting in that with the other hypothalamic structures. Intermediate densities were present in the septohypothalamic, suprachiasmatic, periventricular and paraventricular nuclei as well as in the mammillary complex. Low binding was observed in the other hypothalamic structures. The benzodiazepine binding sites analyzed belong mostly to type II receptors. In an attempt to unravel possible differences related to age, we compared the autoradiographic distribution in three postnatal age ranges. The topographical distribution of these binding sites was almost identical in each period analyzed. We found, however, that benzodiazepine binding is generally low in the neonatal period and a tendency in increasing densities is observed during development. Taken together, these results provide evidence for a large distribution of benzodiazepine binding sites in neonate/infant hypothalamus, suggesting their implication in the development of this brain structure and the maintenance of its various functions.

Localization and developmental pattern of vasoactive intestinal polypeptide binding sites in the human hypothalamus.

Using a quantitative in vitro autoradiographic approach, vasoactive intestinal polypeptide (VIP) binding site densities were compared in the post-mortem hypothalamus of human neonate/infant and adult. The densities were similar during development in most of the hypothalamic nuclei and areas examined underlying the stability of 125I-VIP binding sites in the post-mortem hypothalamus of young and adult individuals. However, the ventral part of the medial preoptic area, the medial, lateral, and supramammillary nuclei were characterized by an increase of 125I-VIP binding with age. In young and adult individuals, the highest densities of hypothalamic 125I-VIP binding sites were detected in the supraoptic and infundibular nuclei; the ependyma; the organum vasculosum of the lamina terminalis; the horizontal limb of the diagonal band of Broca; the ventral part of the medial preoptic area (in adult); the suprachiasmatic, paraventricular, and periventricular nuclei; and the medial and lateral mammillary nuclei in adult. Moderate densities were found in the vertical limb of the diagonal band of Broca, the bed nucleus of the stria terminalis, the ventral part of the medial preoptic area in neonate/infant, the medial and lateral mammillary nuclei in neonate/infant, the supramammillary nucleus in adult, the dorsal hypothalamic area, and the ventromedial nucleus. Low to moderate binding site densities were observed in the other hypothalamic regions of young or adult individuals. The nonspecific binding ranged from 15% of the total binding in the anterior hypothalamus to 20% in the mediobasal and posterior hypothalamic levels. Taken together, these results provide evidence for a large distribution of VIP binding sites in neonate/infant and adult human hypothalamus suggesting the implication of VIP in the development of this brain structure and the maintenance of its various functions.

Asymmetry of brain aromatase activity: region- and sex-specific developmental patterns.

Developmental patterns of aromatase activity (AA) were characterized in individual forebrain regions of the rat at gestational day (GD) 22 and postnatal days (PN) 6 and 15. Aromatase activity was measured separately in homogenates of left and right preoptic area, anterior amygdaloid area, medial amygdaloid nucleus, anterior hypothalamic area and posterior hypothalamic area, by the tritiated water method with [1 beta-3H]-androstenedione as a substrate. Region- and sex-dependent asymmetries of AA with either left-to-right or right-to-left gradients were found. They change between GD22 and PN6 and PN15 according to region-specific patterns. Thus, AA of the male medial amygdaloid nucleus of the left side is higher at GD22, lower at PN6 and equal to the right side at PN15; in females, AA of the left side is lower than AA of the right side at GD22 and higher at PN6 and PN15. In preoptic area, a side difference (left side higher) was only detected in males. Asymmetries may result from differences in the expression of the enzyme by individual cell groups, or from differences in the number of cells per area expressing the enzyme. In either case, the stage-dependent patterns of asymmetry in AA would be expected to influence sex steroid-dependent differentiation processes in individual forebrain areas.

[Ascending effects of the posterior portion of the hypothalamus on electrical activity of the cerebral cortex in the rabbit during postnatal ontogeny]. / Voskhodiashchie vliianiia zadnego otdela gipotalamusa na élektricheskuiu aktivnost' kory bol'shikh polusharii golovnogo mozga krolikov v postnatal'nom ontogeneze.

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.

[Development of the hypothalamic-cortical interrelations in the ontogeny of the cat]. / Izuchenie razvitiia gipotalamo-korkovykh vzaimootnoshenii v ontogeneze koshki.

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.