A Working Module for the Neurovascular Unit in the Sexually Dimorphic Nucleus of the Preoptic Area.

The neurovascular unit (NVU) can be conceptualized as a functional entity consisting of neurons, astrocytes, pericytes, and endothelial and smooth muscle cells that operate in concert to affect blood flow to a very circumscribed area. Although we are currently in a "golden era" of bioengineering, there are, as yet, no living NVUs-on-a-chip modules available and the development of a neural chip that would mimic NVUs is a seemingly lofty goal. The sexually dimorphic nucleus of the preoptic area (SDN-POA) is a tiny brain structure (between 0.001~0.007 mm3 in rats) with an assessable biological function (i.e., male sexual behavior). The present effort was undertaken to determine whether there are identifiable NVUs in the SDN-POA by assessing its vasculature relative to its known neural components. First, a thorough and systematic review of thousands of histologic and immunofluorescent images from 201 weanling and adult rats was undertaken to define the characteristics of the vessels supplying the SDN-POA: its primary supply artery/arteriole and capillaries are physically inseparable from their neural elements. A subsequent immunofluorescent study targeting α-smooth muscle actin confirmed the identity of an artery/arteriole supplying the SDN-POA. In reality, the predominant components of the SDN-POA are calbindin D28k-positive neurons that are comingled with tyrosine hydroxylase-positive projections. Finally, a schematic of an SDN-POA NVU is proposed as a working model of the basic building block of the CNS. Such modules could serve the study of neurovascular mechanisms and potentially inform the development of next generation bioengineered neural transplants, i.e., the construct of an NVU neural chip.

Vascular Influence on Ventral Telencephalic Progenitors and Neocortical Interneuron Production.

The neocortex contains glutamatergic excitatory neurons and γ-aminobutyric acid (GABA)ergic inhibitory interneurons. Extensive studies have revealed substantial insights into excitatory neuron production. However, our knowledge of the generation of GABAergic interneurons remains limited. Here we show that periventricular blood vessels selectively influence neocortical interneuron progenitor behavior and neurogenesis. Distinct from those in the dorsal telencephalon, radial glial progenitors (RGPs) in the ventral telencephalon responsible for producing neocortical interneurons progressively grow radial glial fibers anchored to periventricular vessels. This progenitor-vessel association is robust and actively maintained as RGPs undergo interkinetic nuclear migration and divide at the ventricular zone surface. Disruption of this association by selective removal of INTEGRIN ß1 in RGPs leads to a decrease in progenitor division, a loss of PARVALBUMIN and SOMATOSTATIN-expressing interneurons, and defective synaptic inhibition in the neocortex. These results highlight a prominent interaction between RGPs and periventricular vessels important for proper production and function of neocortical interneurons.

[Participation of muscarinic and nicotinic cholinoreceptors of hypothalamus preoptic area in control of wakefulness and sleep states and of thermoregulation in pigeons Columbia livia].

By using electrophysiological methods, it has been established that muscarinic (M-) cholinergic mechanisms of the ventrolateral preoptic area (VLPA) of pigeon hypothalamus participate in maintenance of wakefulness, whereas nicotinic (N-) mechanisms--in maintenance of the slow-wave sleep. Activation of the VLPA M-cholinergic receptors has been found to be accompanied by an elevation of the brain temperature, by development of peripheral vasoconstriction, and by an increase in the muscle contractive activity. Activation of N-cholinoreceptors leads to a decrease in the brain temperature and development of peripheral vasoconstriction. It is suggested that the VLPA M- and N-cholinergic receptors are involved in different mechanisms of regulation of wakefulness and sleep states and brain temperature in pigeons.

Thread occlusion but not electrocoagulation of the middle cerebral artery causes hypothalamic damage with subsequent hyperthermia.

Moderate changes in body temperature can influence the outcome of cerebral ischemic insults and the effect of drugs. Body temperature was measured continuously for 24 hours in rats subjected to permanent occlusion of the middle cerebral artery (MCA) by either coagulation or thread insertion, and the results correlated with the histology of the hypothalamus. The body temperature did not change after MCA occlusion by coagulation and the hypothalamus was intact in all rats. In contrast, the body temperature rapidly increased from about 38 degrees C to more than 39.5 degrees C after MCA occlusion using intraluminal thread, and hyperthermia continued for at least 6 hours in all rats. Histological evaluation revealed neuronal damage in the preoptic area of the hypothalamus in all rats undergoing thread occlusion. Long duration hyperthermia must be prevented after permanent MCA occlusion when the intraluminal thread occlusion model is used in chronic experiments.

A PET study on brain control of micturition in humans.

Although the brain plays a crucial role in the control of micturition, little is known about the structures involved. Identification of these areas is important, because their dysfunction is though to cause urge incontinence, a major problem in the elderly. In the cat, three areas in the brainstem and diencephalon are specifically implicated in the control of micturition: the dorsomedial pontine tegmentum, the periaqueductal grey, and the preoptic area of the hypothalamus. PET scans were used to test whether these areas are also involved in human micturition. Seventeen right-handed male volunteers were scanned during the following four conditions: (i) 15 min prior to micturition during urine withholding: (ii) during micturition; (iii) 15 min after micturition; (iv) 30 min after micturition. Ten of the 17 volunteers were able to micturate during scanning. micuturition was associated with increased blood flow in the right dorsomedial pontine tegmentum, the periaqueductal grey, the hypothalamus and the right inferior frontal gyrus. Decreased blood flow was found in the right anterior cingulate gyrus when urine was withheld. The other seven volunteers were not able to micturate during scanning, although they had a full bladder and tried vigorously to do so. In this group, during these unsuccessful attempts to micturate, increased blood flow was found in the right ventral pontine tegmentum, which corresponds with the hypothesis, formulated from results in cats, that this area controls the motor neurons of the pelvic floor. Increased blood flow was also found in the right inferior frontal gyrus during unsuccessful attempts at micturition, and decreased blood flow in the right anterior cingulate gyrus was found during the withholding of urine. The results suggest that, as that of the cat, the human brainstem contains specific nuclei responsible for the control of micturition, and that the cortical and pontine micturition sites are predominantly on the right side.

Immunocytochemical evidence for noradrenergic regulation of estrogen receptor concentrations in the guinea pig hypothalamus.

The noradrenergic system interacts with steroid hormones to influence female sexual behavior and gonadotropin release in rodents. Using a double label immunocytochemical procedure for estrogen receptors and dopamine-beta-hydroxylase, we investigated the anatomical relationships between noradrenergic neurons and estrogen receptor-immunoreactive (ER-IR) cells in the brain of ovariectomized female guinea pigs. Dopamine-beta-hydroxylase-immunoreactive (DBH-IR) varicosities were closely associated with ER-IR cells throughout the hypothalamus and preoptic area. This anatomical relationship was observed with almost 80% of the ER-IR cells in the ventrolateral hypothalamus (VLH), an area involved in the regulation of female sexual behavior in guinea pigs. Furthermore, the presence of closely associated DBH-IR varicosities was related to staining intensity of ER-IR neurons. In the rostral VLH, ER-IR neurons with closely associated DBH-IR varicosities stained more darkly than ER-IR neurons lacking this association, suggesting noradrenergic regulation of basal levels of cellular estrogen receptors. These findings provide neuroanatomical evidence suggestive of noradrenergic regulation of estrogen receptor levels in the hypothalamus of female guinea pigs.

Appearance of neurons with glucocorticoid receptors and neurovascular links in the embryonal rat hypothalamus grafted in the third ventricle.

We have investigated the appearance of the transmitter phenotypes of hypothalamic neurons in grafts transplanted into the third ventricle of adult female rats. The grafts were the mediobasal hypothalamus and the preoptic area of 12.5-day-old rat embryos, and were examined 40-100 days later. Wheat germ agglutinin (WGA) was injected into the jugular vein of several animals for the examination of the existence of neurovascular associations. Three days after the injection, WGA appeared to have been incorporated into the neurons in the paraventricular, periventricular, and arcuate nuclei of the host animals. In the grafts, WGA was also seen incorporated in certain neurons which were found immunoreactive for tyrosine hydroxylase (TH), rat corticotropin-releasing factor (rCRF), substance P (SP), or somatostatin (SRIH). Neurons immunoreactive for neuropeptide Y (NPY) and ACTH did not seem to incorporate WGA. These findings suggest that the neurons containing TH, rCRF, SP, or SRIH link with fenestrated capillaries developed in the grafts. The immunoreactivity for glucocorticoid receptor (GR) was detected mainly in the nucleus of certain neurons and glial cells in the grafts as well as in the host hypothalamic neurons. In the grafts, strong GR immunoreactivity was detected in the cells immunoreactive for TH, NPY, and rCRF as in the host animals. It is concluded that the undifferentiated hypothalamic neurons differentiate to synthesize GR as well as definitive peptides and TH in the grafts.

[Morphometric analysis of the vascular network in the preoptic area of the brain in man]. / Morfometrijska analiza vaskularne mreze preopticke areje mozga coveka.

Twenty brains of human beings of both sex aged 17-64 were used for morphometric analysis of the vascular network of preoptic area. Blood vessels of the brain were filled by the mixture od India ink and gelatine. Serial resections 200 microns thick were illuminated by the method of Spalteholz. Standard stereologic parameters--volume density, surface density and the average half diameter of blood vessels were used for the quantification of capillary blood network density. By the comparative test of obtained mean values of males and females no statistically significant differences pertaining to sex and in respect to the size and density of capillary network in preoptic area were confirmed. This fact supported the assumption that although there were no morphologic differences in the blood network changes in various functional states, accompanying neuroendocrine events in the body of adults were in all probability the main and responsible factors inducing greater or less vascularization of specific organs.

[Dynamics of local blood flow in different areas of the hypothalamus during the sleep-wakefulness cycle]. / Dinamika mestnogo krovotoka v razlichnykh oblastiakh gipotalamusa v tsikle bodrstvovanie--son.

In cats with implanted electrodes, the local blood flow (LCBF) was studied in different hypothalamic areas using the electrochemically generated hydrogen. During paradoxical sleep (PS), the level of LCBF increases in the posterior hypothalamus, while decreasing in the anterior hypothalamus and preoptic area. In slow wave sleep (SWS), however, the level of LCBF increases in the anterior hypothalamus and preoptic area, while decreasing in the posterior hypothalamus. These shifts of LCBF during PS are supposed to reflect an enhancement of the posterior hypothalamus functional activity. During SWS the functional activity must be enhanced in the anterior hypothalamus and preoptic area, while being suppressed in the posterior hypothalamus.

Synaptogenesis in the neonatal preoptic area grafted into the aged brain.

The medial preoptic area (POA) of newborn female rats was transplanted into the third ventricle of young adult (2 months of age) and aged (27 months of age) female rats. The grafted POA tissues were examined ultrastructurally 2 months after transplantation. The mean numbers of axodendritic shaft and spine synapses in the POA transplants in both young adult and aged female rats were much greater than those in the medial POA of newborn female rats. These results suggest that the neuronal substrates in the medial POA grafts develop well in the brain of the aged female rats.

Light- and electron-microscopic characterization of electrophysiologically-identified, horseradish peroxidase-injected magnocellular neuroendocrine cells in goldfish preoptic nucleus.

We recorded intracellularly from neurons in the goldfish preoptic nucleus which were antidromically identified by electrical stimulation of the pituitary gland and marked by intracellular injection of horseradish peroxidase for subsequent localization. At the light-microscopic level, labeled neurons resembled profiles of Golgi-impregnated neurons and lay in the magnocellular portion of the preoptic nucleus. Densely labeled axons and dendrites projected to the lateral forebrain bundle, the medial forebrain bundle, fiber tracts in the preoptico-hypophysial tract, small blood vessels and capillaries, the ependymal lining of the third ventricle and toward the preoptic neurons. Occasionally, a lightly-labeled, large perikaryon lay adjacent to a large, heavily-labeled magnocellular neuron. Ultrastructural examination of these identified cells revealed dense reaction product in neuronal perikarya and processes. Heavily labeled perikarya had elaborate networks of endoplasmic reticulum, extensive Golgi apparatus, occasional somatic spines and infrequent axo-somatic contacts from unlabeled neurons. These labeled perikarya which were frequently in close somatic apposition with unlabeled profiles were sometimes adjacent to a large, lightly-labeled perikaryon. A thin glial sheath separated most labeled neurons and processes from brain capillary endothelium. Labeled dendrites had heavily labeled spines and axo-dendritic contacts from unlabeled neurons. Labeled axons abutted unlabeled-axons and -dendrites. Synaptic boutons innervating labeled structures always contained small clear synaptic vesicles and some boutons also contained large dense-core vesicles. These results demonstrate the complex connections of goldfish preoptic magnocellular neuroendocrine cells with other neurons, fiber systems, brain capillaries, ventricular ependyma and the pituitary and provide further support for non-endocrine as well as endocrine functions of magnocellular neurons.

Vascular anatomy of the preoptic region of the brain.

Most investigators are agreed that there are perforating vessels arising from the proximal segments of the anterior cerebral arteries and from the anterior communicating artery. However, there is a wide variation in description of the sites of irrigation of these perforators. Our own studies have led us to believe that these small perforating vessels from the most distal branch of the internal carotid artery are destined ony for the preoptic cellular region, the ventral portion of the most rostral part of the brain, the telencephalon.

[Interrelationships of the neurosecretory cells and capillaries in the preoptic nucleus of the carp]. / O vzaimootnosheniiakh neirosekretornykh kletok s kapilliarami v preopticheskom iadre karpa.

Three layers are tentatively recognized in the wall of a blood capillary of nucleus praeopticus (NP) of the carp, Cyprinus carpio L: the inner layer--endothelium, the middle layer--basement membrane with pericytes, and the outer broken layer containing mostly leucocytes and fibroblast-like cells. 1). The plasmalemma of the neurosecretory cells (NSC) makes a direct contact with a capillary: (a) with the plasmalemma of a sole-like process of the endothelial cell (0.1%), (b) with the basement membrane of the capillary (4.9%), (c) with the plasmalemma of the outer layer cells (41.3%). 2) The plasmalemma of the NSC is separated from the capillary by a glial process (53.7%). The first kind of the contact is frequent in the ventral part (3.7%), and the second one--in the dorsal part (29.4%) of NP. The different relations of the NSC--the capillary of the ventral and dorsal parts are due to heterochronism of their development in ontogenesis.

[Development of neuron-capillary interrelationships in the nuclei of the anterior portion of the human hypothalamus during ontogenesis]. / Osobennosti razvitiia neiron-kapilliarnykh vzaimootnoshenii v iadrakh perednego otdela gipotalamusa cheloveka v ontogeneze.

Three periods in the formation of the spatial arrangement of the neuronal nuclei have been stated: 1) from the prenatal period, infancy including--pronounced decrease in the density of the neuronal cells arrangement; 2) from the childhood up to adolescence--relative stabilization in the hypothalamic cellular composition; 3) mature and old age--secondary decrease in the dencity of the neuronal cells arrangement. Certain peculiarities in the nuclear capillary composition and in their neuronal-capillary relationships have been revealed: during the prenatal ontogenesis, the dencity of the neuronal cells arrangement decreases and their size increases that is followed by decrease in their capillary loops. In postnatal ontogenesis no proportional relationship between the dencity of neuronal cells arrangement and that of capillary network in the nuclei of the anterior hypothalamus was noted.

The arterial and venous blood supply of the preoptic region in the rat.

A study has been made of the arterial and venous circulation of the preoptic region in the rat, using the double Indian ink technique. A detailed description is offered on supply of the nucleus preopticus medialis, lateralis, suprachiasmatis and periventricularis, as well as of the nucleus interstitialis striae criminalis and of the preoptic portion of the medical forebrain bundle. The arteries of the region emerge from the anterior communicans artery and from the anterior cerebral artery. The blood of the region is collected by the anterior cerebral artery. Veins collected by the v. cerebri magna, are also running dorsalwards from the nucleus interstitialis striae terminalis. The blood supply of the organon vasculosum laminae terminalis is described with special regard to its vascular connection with the preoptic nuclei.

The fine structure of the hypothalamic secretory neurons of the white-crowned sparrow, Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae). II. Magnocellular and parvocellular nuclei of the rostral hypothalamus.

The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy. The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and dense-cored granules 1,500-2,200 A in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800-1,000 A in diameter and clear vesicles 500 A in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region. The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 A in diameter. The profiles of axons within the neuropil contain dense-cored granules 800-1,000 A in diameter and clear vesicles 500 A in diameter. The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 A in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya. Occasionally, neurons with granules 1,500-2,200 A in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system. The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 A in diameter.

Relationship between the preoptico hypophysial system and the vascular system in the teleost Rita rita (Ham.).

In Rita rita the internal carotid artery gives rise to hypothalamic and hypophysial arteries. The hypophysial artery directly enters the pituitary and largely contributes to the interface vasculature lying in between the neurohypophysis and the pars distalis which can be considered as an equivalent of the median eminence. Blood vessels from the interface vasculature enter the pars distalis. The hypothalamic artery gives rise to the primary capillary plexus in the infundibular floor and the portal vessels formed by it irrigate the glandular pituitary. Both, at the level of the hypothalamus and at the interface, neurosecretory material might get access to blood vessels. Thus, in Rita rita, not only the typical teleostean type of hypothalamo-hypophysial vascularization is present, but also an incipient tetrapodal pattern is evident.