Identification of the suprachiasmatic nucleus venous portal system in the mammalian brain.

There is only one known portal system in the mammalian brain - that of the pituitary gland, first identified in 1933 by Popa and Fielding. Here we describe a second portal pathway in the mouse linking the capillary vessels of the brain's clock suprachiasmatic nucleus (SCN) to those of the organum vasculosum of the lamina terminalis (OVLT), a circumventricular organ. The localized blood vessels of portal pathways enable small amounts of important secretions to reach their specialized targets in high concentrations without dilution in the general circulatory system. These brain clock portal vessels point to an entirely new route and targets for secreted SCN signals, and potentially restructures our understanding of brain communication pathways.

Assessment of Arterial Configurations of the Suprachiasmatic Region from the Endoscopic Endonasal Perspective: A Cadaveric Anatomical Study.

BACKGROUND: Endoscopic endonasal surgery has proved to offer a practical route to treat suprasellar lesions, including tumors and vascular pathologies. Understanding the different configurations of the anterior cerebral communicating artery (ACoA) complex (ACoA-C) is crucial to properly navigate the suprachiasmatic space and decrease any vascular injury while approaching this region through an endonasal approach. METHODS: An endoscopic endonasal transplanum-transtubercular approach was performed on 36 cadaveric heads (72 sides). The variations of the ACoA-C and feasibility of reaching its different components were analyzed. The surgical area exposure of the lamina terminalis was also quantified before and after mobilization of the ACoA-C. RESULTS: The typical ACoA-C configuration was found in 41.6% of specimens. The following 2 main variations were identified: accessory anterior cerebral artery segment 2 (5, 13.9%) and common trunk of anterior cerebral artery with absence of ACoA (5, 13.9%). Of 101 recurrent arteries of Heubner, 96 (95.0%) were identified within 4 mm proximal or distal to the ACoA. The mean lamina terminalis exposure area was 33.1 ± 16.7 mm2, which increased to 59.9 ± 11.9 mm2 after elevating the ACoA. CONCLUSIONS: A considerable amount of variation of the ACoA-C can be found through an endoscopic endonasal transplanum-transtubercular approach. These configurations determine the feasibility of lamina terminalis exposure and the complexity of reaching the ACoA. Assessment of ACoA morphology and its adjacent structures is crucial while approaching the suprachiasmatic through a transnasal corridor.

[Relationship between vascular senescence and impaired circadian rhythmicity].

Aging is associated with impairment of various circadian rhythms of body, including daily rhythms of blood pressure, core body temperature, and the sleep-waking cycle. In mammals circadian rhythmicity is under control of molecular pacemaker that is composed of products of clock genes. Recent evidence suggests that cellular senescence impairs circadian rhythmicity and contributes to various age-associated diseases. Senescence decreases the ability of cells to transmit circadian signals such as nitric oxide to their clocks. The regulation of clock gene expression may be a novel strategy for treatment of age-associated impairment of circadian rhythmicity.

The cortisol awakening response in context.

The cortisol awakening response (CAR) is a crucial point of reference within the healthy cortisol circadian rhythm, with cortisol secretion typically peaking between 30 and 45 min post awakening. This chapter reviews the history of investigation into the CAR and highlights evidence that its regulation is relatively distinct from cortisol secretion across the rest of the day. It is initiated by awakening, under the influence of the hypothalamic suprachiasmatic nucleus, and "fine tuned" by a direct neural input to the adrenal cortex by the sympathetic nervous system. This chapter also examples the CAR in relation to other awakening-induced processes, such as restoration of consciousness, attainment of full alertness, changes in other hormones, changes in the balance of the immune system, and mobilization of the motor system, and speculates that there is a role for the CAR in these processes.

Transient short free running circadian rhythm in a case of aneurysm near the suprachiasmatic nuclei.

A free running circadian rest-activity cycle is rare in sighted individuals living in a normal environment. Even more rare is a periodicity shorter than 24 hours, as observed in actigraphic recordings in a female patient during convalescence after a whiplash injury in a car accident. The documented free running period was 22.5 hours for 19 days. During the subsequent weeks re-entrainment occurred following re-establishment by a social zeitgeber, with a slightly early circadian phase of nocturnal melatonin onset relative to a late sleep period. Magnetic resonance imaging and cerebral angiography showed an aneurysm at the bifurcation of the right internal carotid artery, close to the circadian pacemaker structure (the suprachiasmatic nuclei), which was later occluded.

Suprachiasmal carotid-ophthalmic artery aneurysm--report of two cases.

Two rare suprachiasmal carotid-ophthalmic artery aneurysms, one large and one giant, were discovered incidentally. The patients had no visual disturbances. Angiography showed superomedial projection of the sac. The aneurysms were clipped via an ipsilateral pterional approach. A suprachiasmal carotid-ophthalmic artery aneurysm is indicated when preoperative angiography reveals a superomedial carotid-ophthalmic artery aneurysm without visual disturbances. Direct surgery to clipp a suprachiasmal aneurysm should be carried out to prevent rupture of these frequently large aneurysms.

[Morphometric analysis of the vascular network of the suprachiasmatic and paraventricular nucleus in the human brain]. / Morfometrijska analiza vaskularne mreze suprahijazmaticnog i paraventrikularnog jedra mozga coveka.

The aim of the study is to discover, the sources of vascularization, vascular areas, the size and density of the capillary network in the suprachiasmatic and the paraventricular nuclei of postnatal human brains of both sexes. The brain blood vessels under examination were filled with a mixture of India ink and gelatin. The serial paraffin sections of 200 microns cleared after Spalteholz. In the vascularization of the suprachiasmatic and the paraventricular nuclei, two arterial stems, take part with their branches (a. cerebri anterior and a. communicans anterior). In order to quantify the density of the capillary network, the authors used the standard stereologic parameters - volume density, surface density and mean radius of blood vessels. The comparative testing of the mean values obtained in male and female subjects did not reveal any significant sex - dependent differences regarding the size and density of the capillary network in the suprachiasmatic and the paraventricular nuclei of the human brain.