The temperature-dependent compartmentation of the ‘extracellular space’ in mouse brain slices as revealed by the markers: Inulin, sucrose, d-mannitol, d-sorbitol and sulfate

Abstract

Summary A new HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid)-buffered medium for incubating brain slices is described. The penetration of the ‘extracellular space markers’, inulin, sucrose, d -mannitol, d -sorbitol and sulfate into mouse cerebrum slices is greater at 37°C than at 0°C, indicating the existence of asecond marker (inulin) space for these substances. This second space is a tissue compartment which is accessible to the marker substance at 37°C but not at 0°C. At both temperatures, the smaller the marker molecule the larger the indicated extracellular space. A second inulin space also exists in cat and guinea pig brain slices. The penetration of d -glutamate into mouse cerebrum slices at 0°C is equal to the penetration of inulin at 37°C. This shows the continuing existence at 0°C of a tissue compartment corresponding to the 37°C inulin space. Other amino acids studied at 0°C penetrate more than d -glutamate. l -Arginine and l -histidine show concentrative uptake after 80 min incubation. The second marker space may consist of a ramifying system of tubules extending throughout a cell body and connecting to the extracellular space by a micropore.