Abbott N J, Bundgaard M, Cserr H F
J Physiol. 1985 Nov;368:213-26. doi: 10.1113/jphysiol.1985.sp015854.
Cephalopod molluscs have complex brains and behaviour, yet little is known about the permeability of their blood-brain interface. The accompanying paper characterized the fluid compartments of the brain and presented evidence for restricted permeability of the blood-brain interface to albumin. The present paper investigates the permeability of the interface to small non-electrolytes. [14C]Polyethylene glycol (PEG, mol. wt. 4000), and [51Cr]EDTA (mol. wt. 342) were injected intravenously or intramuscularly, and their penetration into brain and muscle studied up to 48 h. Tracers equilibrated with muscle interstitial fluid (ISF) at relatively short times, but in brain ISF reached only 0.5-0.65 X their plasma concentration. This is qualitative evidence for the presence in brain of a barrier to these molecules and an efficient drainage mechanism for ISF. Quantitative treatment of the uptake data allows calculation of the permeability X surface area product (PS) and the permeability coefficient (P). For the brain PS and P are in the range 1-3 X 10(-4) ml g-1 min-1 and 1-3 X 10(-8) cm s-1 respectively, (PEG), and 3 X 10(-4) ml g-1 min-1 and 3-4 X 10(-8) cm s-1 respectively (Cr-EDTA). The P values are close to those reported for mammalian brain. Assuming that the lack of equilibration in brain is due to ISF flow, the rate of flow can be calculated. Values for vertical and optic lobe are approximately 0.2 microliter g-1 min-1, again close to those reported for mammalian brain. It is concluded that the tightness of the Sepia blood-brain barrier approaches that of mammals, and a flowing ISF system is present. An association between a tight barrier and higher central nervous system integrative function is suggested. The significance of these findings for the evolution of control of the brain microenvironment is discussed.
头足类软体动物拥有复杂的大脑和行为，但人们对其血脑屏障的通透性却知之甚少。随附的论文描述了大脑的体液区室，并提供了证据表明血脑屏障对白蛋白的通透性受限。本文研究了该屏障对小的非电解质的通透性。将[¹⁴C]聚乙二醇（PEG，分子量4000）和[⁵¹Cr]乙二胺四乙酸（EDTA，分子量342）静脉内或肌内注射，并在长达48小时内研究它们向大脑和肌肉的渗透情况。示踪剂在相对较短的时间内与肌肉组织间液（ISF）达到平衡，但在大脑ISF中仅达到其血浆浓度的0.5 - 0.65倍。这是这些分子在大脑中存在屏障以及存在ISF有效引流机制的定性证据。对摄取数据的定量处理可以计算通透性×表面积乘积（PS）和通透系数（P）。对于大脑，PS和P分别处于1 - 3×10⁻⁴毫升·克⁻¹·分钟⁻¹和1 - 3×10⁻⁸厘米·秒⁻¹的范围内（PEG），以及分别为3×10⁻⁴毫升·克⁻¹·分钟⁻¹和3 - 4×10⁻⁸厘米·秒⁻¹（铬 - EDTA）。这些P值与报道的哺乳动物大脑的值相近。假设大脑中缺乏平衡是由于ISF流动所致，则可以计算流速。垂直叶和视叶的值约为0.2微升·克⁻¹·分钟⁻¹，同样与报道的哺乳动物大脑的值相近。结论是，乌贼血脑屏障的紧密程度接近哺乳动物，并且存在一个流动的ISF系统。有人提出紧密屏障与更高的中枢神经系统整合功能之间存在关联。讨论了这些发现对大脑微环境控制进化的意义。
