The angiogenesis of the micrencephalic rat brains caused by methylazoxymethanol acetate. III. Internal angioarchitecture of cortex.

The intracortical angioarchitecture of normal and micrencephalic rat brains was examined. The neuroblast migration was disturbed by injection of the neurotoxin methylazoxymethanol acetate, administered on day E14. The internal vascularization of the malformed cortex showed severe damage to the layered distribution of vascular trunks in contrast to controls. A pathological course and marked variability in the density of the radial vessels were seen in the parieto-occipital areas, in which the neuroblast migration was most severely affected. These observations show the decisive role of neuroblast migration and maturation in the development of the cortical angioarchitecture.

Spatial correlation between sensory regions and the drainage fields of pial veins in rat cerebral cortex.

Visual and somatosensory evoked potentials were mapped in the cerebral cortex of adult rats and, after filling the cerebral arteries and veins with dye, the mappings were then compared to the distribution of pial veins. A close relationship was found between the position, size and shape of the occipital venous drainage field and the distribution of visual evoked potentials with high amplitudes and short latencies. Accordingly, such potentials evoked by stimulation of the forepaw and tailroot were confined to the fronto-parietal drainage field. In the case of individual variations in the expansion and shape of sensory areas, the medial and lateral borders of the occipital drainage field and the medial border of the fronto-parietal drainage field covaried. Only at the common border between these two drainage fields, visual evoked potentials with small amplitudes and long latencies extended into the parietal drainage field and overlapped with somatosensory evoked potentials. This overlapping area corresponds in position to the anterior part of the peristriate cortex. A comparison between the vascular organization and cytoarchitectonic maps of the rat cortex indicates that other parts of the characteristic pattern of venous drainage fields may also correlate with the cytoarchitectonic and functional organization of the cerebral cortex. These observations suggest that during morphogenesis the formation of sensory projections to the cerebral cortex may interact with the angiogenesis, mainly with the development of veins.

Constant position of the superficial cerebral veins of the rat: a quantitative analysis.

The normal anatomical position of the point of junction of the superficial cerebral veins with the superior sagittal and transverse sinuses of the rat was studied with an analytical mathematical method. There were eight fixed veins, each characterized by a constant point of juncture having minimal variance. The findings indicate that the points of juncture between large veins and sinuses are developmentally fixed and that there is a definite order in the number and the territories of the large veins.

The angiogenesis of micrencephalic rat brains caused by methylazoxymethanol acetate. I. Superficial venous system. A quantitative analysis.

The angiogenesis of the rat cerebrum was studied under pathologic conditions caused by the administration of the neurotoxin methylazoxymethanol acetate (MAMAc) in the time (E14) of neuroblast migration. The sinovenous junction of the main superficial cerebral veins and the morphological changes of the veins were examined by a quantitative analytic method. The hypoplastic areas of the brains showed extremely malformed venous systems with pathologic changes of the sinovenous junctions depending on the degree of disturbance of the neuroblast migration. These findings suggest the primary role of the neuronal maturation in the angioarchitectonic development and the direct dependency of the vascular differentiation on the neuroblast migration of the drained territory.

The angiogenesis of micrencephalic rat brains caused by methylazoxymethanol acetate. II. Superficial and basal arterial system.

The angioarchitecture of the superficial and basal arterial system of the hypoplastic rat brain caused by the administration of the neurotoxin, methylazoxymethanol acetate (MAMAc), at the time of neuroblast migration was studied. Increased variation of the arterial branching of the basal main stem of arteries and local vessel changes were observed. The findings suggest a close relationship between vascular and neuronal development, showing a generalized disturbance and local adaptation of vasculature to the altered neuronal architecture of the corresponding hypoplastic areas.

Blood supply of the rat hypothalamus. VII. The lateral hypothalamus (medial forebrain bundle).

Using the double ink-filling technique the arteries and veins of the lateral hypothalamus are described in detail. This region occupied mainly by the fibres and interposed cells of the medial forebrain bundle is supplied by some own arteries and branches of the large basal vessels. Most of the arteries running to the rostral part of the lateral hypothalamus originate from the internal carotid, others belong to the anterior and middle cerebral arteries. Blood supply of the middle part comes from the middle hypothalamic and three tuberal arteries. All arteries of the caudal part originate from the posterior communicans. The abundant drainage of the lateral hypothalamus is collected by the basal and anterior interpeduncular veins from the rostral two-thirds and the caudal one-third, respectively.

Blood supply of the rat hypothalamus. VI. Posterior region of the hypothalamus (nucleus hypothalamicus posterior, nuclei praemammillares, nucleus supramammilaris, mammilary body).

It was shown by the double ink-filling technique that the arteries of the rat premammillary region and mammillary body arise from the a. communicans posterior while these areas are drained by the anterior interpeduncular vein. Disregarding some minor overlaps and anastomoses, the blood supplies of the two territories are independent of each other and from the neighbouring areas of the hypothalamus, diencephalon and mesencephalon. Arteries of the premammillary region arise from the premammillary artery, except for some branches of the posterior tuberal and interpeduncular arteries. The mammillary body is supplied by three mammillary arteries (anterior, posterior and lateral). The premammillary region drains into the anterior and posterior premammillary veins. Venous blood of the mammillary body is collected by the anterior and posterior mammillary veins which end in the anterior interpeduncular vein. The circulation of individual premammillary and mammillary nuclei is described in detail.

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.

Blood supply of the rat amygdala.

The cerebral vessels of the rat were filled with inks of different colours. The topography of the vessels of the amygdala were reconstructed from serial sections. The circulation of the individual amygdaloid nuclei was studied in detail. The arteries of the amygdala arise from the deep and cortical branches of the internal carotid and middle cerebral arteries. Eight major arteries were found to supply blood to the amygdala. All amygdaloid nuclei receive branches from both arterial trunks. The vast majority of the veins are collected by the middle cerebral and basal veins. Only a small fraction drains into the hippocampal vein. Of particular importance are the veins ending in the basal vein and those cortical ones that run in the rhinal sulcus. All amygdaloid nuclei have a multidirectional drainage.

Blood supply of the rat hypothalamus. V. The medial hypothalamus (nucleus ventromedialis, nucleus dorsomedialis, nucleus perifornicalis).

Using the India ink double-perfusion technique, the blood vessels of the rat's medial hypothalamus were reconstructed from serial sections. The area studied comprised the ventromedial, dorsomedial and perifornical nuclei. The arterial supply of this territory comes from the middle hypothalamic and the anterior, middle and posterior tuberal arteries. The drainage is strictly undirectional: ventralward by the anterior, middle and posterior ventromedial, the posteromedial and posterolateral hypothalamic veins, all ending in the basal vein. The arteries of the ventromedial and dorsomedial nuclei are distinct from those of the arcuate nucleus and median eminence, and their drainage is not connected with the portal vessels. The nuclei studied, even at the levels of their subdivisions, possess own arteries whose territories of supply can well be distinguished with a minimum of overlap. The topography of these arteries is described in detail. The medial hypothalamus has no vascular connections with other regions of the diencephalon including the thalamus.

Blood supply of the rat hypothalamus. IV. Retrochiasmatic area, median eminence, arcuate nucleus.

The vascular supply of the rat hypothalamo-hypophyseal complex was studied by aid of a double injection technique (two dyes different in colour injected successively). The vascular bed of the median eminence, the arcuate nucleus, and the retrochiasmatic area are intimately interconnected among themselves, but isolated from the vascular system of all other parts of the hypothalamus. The arterial supply of this ensemble of the medial basal hypothalamus is common from the hypophyseal arteries, via the primary plexus and the specific vascular loops of the median eminence. From here a separation of the vascular bed leads the blood flow towards the pituitary portal vessels on the one hand, and over a subependymal vascular network towards the arcuate nuclei on the other. The venous drainage of the arcuate nuclei and the retrochiasmatic area is secured by a special set of tuberal and retrochiasmatic veins. --The unity of the vascular bed of the median eminence, arcuate nucleus, retrochiasmatic area complex, with a blood flow largely in the direction indicated by this sequence, is of considerable importance for the interpretation of the results of experimental interference with this region.

The arterial and venous blood supply of the septum pellucidum in the rat.

The arterial and venous systems of the rat's septum pellucidum has been studied by means of the perfusion technique. The arteries may be classified into three groups. The branches of each of the three groups originate from the a. hemispherica and enter the septum from the frontal direction. The veins may be divided into an anterior and a posterior group. The anterior veins flow through the v. subcallosa into the sinus cavernosus, the posterior veins into v. cerebri magna. The arterial and venous blood supply of the individual nuclei of the septum are compar independent.

Blood supply of the rat hypothalamus. III. Anterior region of the hypothalamus (nucleus suprachiasmatis, nucleus hypothalamicus anterior, nucleus periventricularis).

The arterial and venous blood supply of the anterior hypothalamus was studied by means of double perfusion technique. The angiotopography and cytoarchitecture of the hypothalamus were compared on serial sections by accounting for the three-dimensional coordinates. A detailed description is given of the arteries and veins contributing to the blood supply of the suprachiasmatic, the anterior hypothalamic and the periventricular nuclei. The topography of the arterial and venous trunk on the base surface of the rat diencephalon is described, as well as that of the larger branches which enter from below and pass through the anterior hypothalamus.