In vivo microscopy of the cerebral microcirculation using neonatal allografts in hamsters.

Abstract

Studies were performed to characterize the morphology and vascular reactivity of the allografted cerebral microcirculation. Cerebral cortical tissue was allografted into the cheek pouch of the hamster so that cerebral parenchymal vessels could be studied. The vascular morphology was characterized by a large number of looping vessels. The ultrastructural examination indicated viable cerebral tissue containing typical vessels, that is, "tight" junctions, not like those of the cheek pouch. Also, the microvasculature was impermeable to 150, 70, and 20 kDa fluorescein isothiocyanate dextrans. Angiotensin II and norepinephrine caused constriction of the cerebral vessels whereas adenosine caused dilation. Isoproterenol did not affect cerebral arterioles; however, it dilated cheek pouch arterioles. Thus, this preparation provides a satisfactory model for studying the living cerebral microcirculation. V isualization of the surface vessels of the in situ brain has been used extensively to study the cerebral microcirculation. With this technique, it has been shown that topical application of norepinephrine 1 and angiotensin II 2 -3 constricts, whereas adenosine 4 dilates, pial vessels. However, because of the lack of a suitable experimental preparation, no information is available concerning the responsiveness of in vivo cerebral parenchymal vessels to various vasoactive drugs. The present study describes such a preparation in terms of its microvascular morphology and its vascular reactivity to several endogenous agents. The preparation provides a unique model for studying the cerebral microcirculation in normal and pathological states. Materials and Methods Allograft ProcedureNeonatal hamsters (<24 hours old) were used as donors for the cerebral tissue that was subsequently allografted into the cheek pouches of adult female hamsters weighing 120-160 g. This allograft procedure, described by Greenblatt et al 5 and modified by Click et al, 6 was completed under sterile conditions. Using sterile techniques, longitudinal slices of cerebral cortex from decapitated neonate hamsters were placed in sterile lactated Ringer's solution. The recipient hamster was anesthetized with sodium pentobarbital (6.0 mg/100 g body wt i.p.); the hair on the left side of the head was shaved and the skin was cleaned with water, washed with hexachlorophene detergent cleanser, and covered with povidone-iodine. After the cheek pouch was everted and cleaned with warm water, a baseplate attached to a holder was inserted into the cheek pouch. A longitudinal incision was made in the skin exposing the underlying cheek pouch membrane, and the avascular layers were removed. A small slice (<1 x 1 mm square) of cerebral cortex was positioned on the cheek pouch membrane and penicillin G (6,000 units) was placed around the edge of the membrane. The top plate, containing a plastic wrap-covered window, was inserted over the baseplate and sealed. The skin was secured around the top plate with a purse-string suture, and the top plate was sealed with surgical tape. ...

Reduced angiotensin II levels cause generalized vascular dysfunction via oxidant stress in hamster cheek pouch arterioles

“…low PRA associated with low renin hypertension and increased cardiovascular mortality in humans (68), often goes unnoticed. In the present study, the role of ANG II in maintaining vascular function and preventing oxidant stress in the terminal microcirculation was directly tested for the first time in a novel experimental model that is also suitable for investigation of microvascular function with implanted chambers and in allografts of multiple parenchymal tissues (8, 21, 32, 33). …”

Prostaglandins Contribute to Impaired Angiotensin II–Induced Cerebral Vasodilation after Brain Injury

“…Some reports indicate that regionally infused or topically applied AII results in generalized or local cerebral vasoconstriction in rabbits (Reynier-Rebuffel et al, 1983), hamsters (Joyner et al, 1988), and cats (Mayhan et al, 1988;Wei et al, 1978). Conversely, others reported that AII elicits moderate pial vasodilation in the newborn pig (Meng and Busija, 1993), rabbit (Haberl et al, 1991), and rat (Haberl et al, 1990).…”

Escherichia coli 0111 B4 Lipopolysaccharide Given Intracisternally Induces Blood-Brain Barrier Opening during Experimental Neonatal Meningitis in Piglets

“…This is the first in vivo study determining both the time needed for BBB leakage and the quantitative severity of the permeability disturbances of the brain microvasculature during experimentally induced meningeal bacterial infections in newborns. The suitability of pial-arachnoid vessels for the study of BBB function has previously been demonstrated (15,16,20). The affected vessels with increased NaF permeability are the postcapillary venules, which are the most vulnerable vascular structures with regard to permeability within the CNS and which also behaved similarly to other noxa, such as hypertension, acidosis, and hypoxemia, and to challenge with bradykinin and histamine (14, 15, 2 1).…”

“…The permeability of the BBB can also be followed intravitally by a fluorescence photomacroscope (15)(16)(17). The BBB is tight for intravascular tracers physiologically, but certain injuries induce a BBB leakage.…”