{'fraction_non_alphanumeric': 0.02349570200573066, 'fraction_numerical': 0.011461318051575931, 'mean_word_length': 5.0625, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
An improved closed cranial window technique for investigation of blood-brain barrier function and cerebral vasomotor control in the rat.

A modification of the closed cranial window technique for small laboratory animals is presented. The method facilitates investigation of blood-brain barrier permeability in association with studies of the cerebrovascular response under normal and pathological conditions. Following trephination and preparation of the pia-arachnoid surface, the skull defect is closed again by sealing a cover glass onto a wall of dental cement surrounding the cranial window. The intracranial pressure can then be studied and experimentally manipulated. Care is taken to maintain normal blood-brain barrier function to a small barrier indicator (Na(+)-fluorescein, MW: 376). This is accomplished by opening the skull and dura mater under a column of paraffin oil to avoid exposure of brain tissue to atmospheric pressure. Reactivity of the cerebral surface vessels was assessed during hypercapnia at an arterial PaCO2 of 50.8 +/- 1.1 mm Hg. It was found that small arterioles of 20-50 microns phi had a significantly larger CO2-response than large arterioles of 50-100 microns phi. Pial venules did not respond at all. Superfusion of the cranial window preparation at a rate of 5 ml/h with buffered artificial CSF was tolerated for hours. No alterations of arteriolar or venular diameters nor opening of the blood-brain barrier to Na(+)-fluorescein was observed. These technical modifications enable us to employ a closed cranial window model in small laboratory animals for studies of cerebral microcirculation and blood-brain barrier function under normal as well as under pathological conditions related to brain damage.