摘要:

In experiments carried out on adult rabbit "chest-head" preparations the volume changes of the exposed brain (BrV) were determined in repeated tests during a controlled increase of the systemic venous pressure (SVP) of about 13 mm Hg. The changes of both SVP and BrV were usually parallel at the onset of the experiments, but when the brains became preedematous hysteresis appeared in the plots of their relationships. The hysteresis increased gradually (sometimes with periods of partial decrease) thus indicating a delay in the draining of blood from the brain's venous system and in the removal of excess extracellular fluid from the cerebral tissue. Evidence for water filtration through the capillary walls during increase of the SVP, and, thus, of brain intravascular pressure, was obtained by detecting the dynamics of [Na±] and [K ±] in the extracellular fluid of the cerebral cortex by ion-selective electrodes. This process appeared reversible in normal brains while in the preedematous ones the excessive water filtration resulted in brain edema. The preedematous state of the brain is believed to be caused by changes of the mechanical properties of brain tissue and/or by changes in osmolarity.

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Adenosine and adenine compounds (AMP, cyclic AMP, ADP and ATP) markedly dilated feline and human pial arteries in vitro, the effect being more prominent with increasing tone of the vessel (active tonic contraction induced by prostaglandin F2r, or serotonin). In contrast, the various adenine compounds were unable to produce any dilatation of extracranial arteries tested (branches of lingual, external maxillary, and superficial temporal arteries). The degree of dilatation depended upon the perivascular potassium concentration, so that low potassium increased Emax and reduced ED60 values. Possible involvement of adenine compounds in the vasodilatory phase of the migraine attack is discussed.

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Local cerebral blood flow (LCBF) in the conscious rat was estimated with one of 3 radiotracers -14C-antipyrine, 14C-iodoantipyrine or 3H-nicotine. A tracer was infused intravenously at a constant rate and blood concentration was followed until the animal was killed by decapitation. Tracer concentration was then measured in each of 14 brain regions. The Kety-Schmidt analysis was applied to the data with UCantipyrine and "C-iodoantipyrine. The results confirmed findings of Sakurada et al. (1978) that 14C-iodoantipyrine provides LCBF's that are twice those obtained with uC-antipyrine and that approximate LCBF's found with an inert gas. LCBF was calculated from the 3H-nicotine data by assuming complete extraction of tracer from blood by brain. This assumption was approximated for infusion times of 50 sec or less, when LCBF's derived with 3H-nicotine generally did not differ significantly from LCBF's obtained with "C-iodoantipyrine. Fifty-sec 3H-nicotine-derived flows for the pineal and pituitary glands were, respectively, 2.59 ± 0.36 (SEM) cm3 g ' min1 and 1.28 ± 0.08 cm3 g l min 1. LCBF's calculated for 70 sec to 240 sec of 3H-nicotine infusion were lower than 50-sec values due to back-diffusion, but nevertheless were as high as "C-antipyrine LCBF's due to the marked binding of tracer by brain tissue. The results supported the conclusion of Sakurada et al. (1978) that iodoantipyrine is the non-gaseous agent of choice for measuring LCBF precisely, but also showed that short infusion schedules with nicotine provided good estimates of LCBF.

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1979

数据来源: OVID