REGIONAL DISTRIBUTION OF COLCHICINE‐BINDING (MICROTUBULAR) PROTEIN IN THE RAT BRAIN

— The relative concentrations of microtubular protein (tubulin) in regions of rat brain were determined by taking advantage of its specific property of binding colchicine. In comparison with other tissues, all regions of the brain were rich in tubulin. The cerebral cortex, thalamus and hypothalamus had essentially the same concentration. The cerebellum and brain stem had a lower concentration (about 60 per cent of the cortical level). Although the functional significance of these differences is not clear, they may relate to two proposed functions of microtubules–cytoskeleton and cytoplasmic transport. The complex geometry of neurons and many glial cells with ramified processes must require extensive systems for maintaining shape and an active cytoplasmic transport.