Microangioarchitecture of rat parietal cortex with special reference to vascular "sphincters". Scanning electron microscopic and dark field microscopic study.

Abstract

SUMMARY Microangioarchitecture of the rat parietal cortex was studied by means of scanning electron microscopy and dark field microscopy. The richest supply of blood vessels in the parietal cortex was found in layer HI + IV and layer V, where 2 isolated plexuses of microressels were prominent. Tbe appearance of the plexuses was quite different between motor and sensory areas. In the motor area the capillary plexuses were narrow and compact, while in sensory area the plexuses were wide and diffuse.Characteristic ring formations, called ring-shaped-compressions in the present study, were frequently observed at branching sites of arterioles. The ring-shaped-compression probably corresponds to the precapillary sphincter. A similar structure was also seen in capillaries and venules and, therefore, it is likely that not only arterioles, but also capillaries and eren venules, can actively change diameter to control cerebral blood flow. Stroke, Vol 12, No 5, 1981BLOOD FLOW in the cerebral cortex changes under conditions such as cerebral thrombosis, 1 ' intracranial hypertension 4 '' and abnormal systemic blood pressure.* 17 It is important to understand the underlying mechanisms which control blood circulation within the cerebral cortex. There is a lack of morphological studies of small intracortical blood vessels which are responsible for cerebral microcirculation, although much has been known about extrinsic vessels and their neurogenic" 1 " and metabolic 10 ' " reactions. In the present study the basic differences of angioarchitecture of the somatomotor and somatosensory cortical areas have been studied by means of the scanning electron microscopy (SEM) and dark field microscopy. New information has been obtained about the active site in microvessels which constrict or dilate to control the cerebral microcirculation. Materials and MethodsTwenty albino rats of the Wistar strain (20O-250g) were used. The abdominal aorta and the inferior vena cava were cannulated with polyethylene catheters under sodium pentobarbital anesthesia (50 mg/kg, i.p.). The animals were then kept in an oxygen chamber filled with 95% O, and 5% CO,. Concurrently with exsanguination from the inferior vena cava, perfluochemical artificial blood" (Fluosol-43, The Green Cross Corporation) was injected through the abdominal aorta. The Po, and Pco, were kept at 400-500 mm Hg and 35-40 mm Hg, respectively. When the total circulating blood was exchanged with Fluosol-43, the animal was perfused with 250 ml of mixed solution of 4% glutaraldehyde and 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4) for 7 m at room temperature. After perfusion fixation, the whole body of the animal was immersed in the same solution for 2 days (postfixation). The materials were further processed for dark field microscopy and SEM, as described below. Dark Field MicroscopyAfter fixation the brain was cut into coronal serial 80 nm thick sections with a vibratome. Serial sections were mounted on gelatine-coated glass slides and dried at room temperature. Sections were obser...

The Vascularization of the Pituitary Gland of the Chicken (Gallus domesticus). A Scanning Electron Microscope Study of Vascular Corrosion Casts.

“…On arteriolar branches of the infundibular and neural-lobe arteries, we found circular constrictions indicating the sites of structures capable of regulating blood flow toward the median eminence and neural lobe. Similar structures have been described at branching sites of cast arterioles in the rat parietal cortex (NAKAI et al, 1981). Conspicuous deep constrictions, caused by intra-arterial cushions at these sites, have also been noted at the origin of the hypophyseal arteries in the rat (MURAKAMI et al, 1993).…”

Control of Brain Capillary Blood Flow

“…Peppiatt et al (2006) revealed that this portion (capillary junction) is rich in pericytes. The term precapillary sphincter has been used to imply the functional significance of the area; that is, a region of varied lengths, up to 100 mm or more, which controls blood flow to the capillary bed under physiological conditions (Nakai et al, 1981). Whether ECs on the precapillary arterioles have an essential role in the mechanisms controlling the precapillary sphincter has never been evaluated in vivo.…”

Layer-Specific Dilation of Penetrating Arteries Induced by Stimulation of the Nucleus Basalis of Meynert in the Mouse Frontal Cortex

“…Of the three types of penetrating arteries reported, 19 we focused on relatively large penetrating arteries that travel to deep cortical layers, to measure precisely the diameter of the arteries, and to analyze the depth dependence of diameter changes. It was shown that small diameter arteries had a territory of only the upper layer cortex.…”

“…It was shown that small diameter arteries had a territory of only the upper layer cortex. 19 A total of six penetrating arteries from five animals were used for analysis of the time course of response to the NBM stimulation by cross-sectional imaging 20 at each cortical depth, including the cortical surface, in a 50-mm step. A train of 500 electrical pulses (50 Hz for 10 seconds) were repeated with an interval of 1 minute, according to a previous result showing that increased blood flow after 10-second stimulation of the NBM returns to control level within 20 to 30 seconds after the end of stimulation.…”