For half a century, the human brain was believed to contain about 100 billion neurons and one trillion glial cells, with a glia:neuron ratio of 10:1. entire human brain, and a range of 40C130 billion glial order KU-55933 cells. We evaluate how the claim of one trillion glial cells originated, was perpetuated, and eventually refuted. We compile how numbers of neurons and glial cells in the adult human brain were reported and we examine the reasons for an erroneous consensus about the relative large quantity of glial cells in human brains that persisted for half a century. Our review includes a brief history of cell counting in human brains, types of counting methods that were and are employed, ranges of previous estimates, and the current status of knowledge about the number of cells. We also discuss implications and effects of the new insights into true numbers of glial cells in the human brain, and the promise and potential impact of the newly Rabbit Polyclonal to AP2C validated isotropic fractionator for reliable quantification order KU-55933 of glia and neurons in neurological and psychiatric diseases. and this web is probably the principal seat of inteligence. (page 171, Nansen, 1886, his italics).Glees, 1955: It is well worth mentioning Nansens opinion that this material [Leydigs dotted material = plaiting of nerve-tubes and fibrillae] was the seat of intelligence as it increases in size from the lower to the higher forms of animal. (cites Nansen, 1886)Galambos, 1961: Nansen said neuroglia was the seat of intelligence, as it increases in size from the lower to the higher forms of animal. (cites Glees 1955 footnote)Fields, 2009: Nansen observed in 1886 that glia might be the seat of intelligence, as [their number] increase in size from the lower to the higher forms of animal. (cites Galambos, 1961)Verkhratsky and Butt, 2013: Nansen postulated that neuroglia was the seat of intelligence, as it increases in size from the lower to the higher forms of animal (cites Galambos, 1961). Open in a separate window *Nerve-tubes are present in great plenty in the dotted material (Nansen, 1886, page 124) Accordingly, Franz Nissl was the first to notice the prevalence of glial cells in mammalian cortices (Nissl, 1898; also reviewed in Herculano-Houzel, 2014), while the GNR was first calculated and reported for a major part of the human brain by Mhlmann (1936). Mhlmann established that this approximate GNR (Prozentgehalt der Nerven und der Gliazellen) of the grey matter of the human cerebral cortex is about 1.5, a value that since has been widely confirmed (Table 2). He also conducted a detailed developmental study that revealed how the GNR in cortex changes from your newborn (GNR = 0.3:1) to the aged adult (GNR = 2:1). This showed that this GNR is usually age-specific and that glia-neuron relations switch as the brain matures. From your 1950s until the 1980s, the GNR was called glia index (Friede, 1953, 1954), glia/neuron index (Brizzee and Jacobs, 1959), or glia/nerve cell index (Hawkins and Olszewski, 1957). Altman (1967) was the first to use interchangeably the terms glia index and glia-neuron ratio (GNR), while Bass et al. (1971) order KU-55933 and some subsequent investigators advocated the use of the reciprocal of the GNR: the neuron/glia ratio (Th?rner et al., 1975; Diamond et al., 1985; Terry et al., 1987; Leuba and Garey, 1989), the rationale being that this neuronal density varies much more than the glial cell density (Bass et al., 1971; Reichenbach, 1989). Bass et al. (1971) C incorrectly as it turned out C assumed that the number of endothelial cells in brains was negligible: since the vascular cell portion is relatively small, the neuron/non-neuron ratio(n) essentially equals the neuron/glia ratio. Others work showed that as much as one third of non-neuronal cells were endothelial cells in mammalian, including human, CNS (Blinkov and Glezer, 1968; Brasileiro-Filho et al., 1989; Bjugn and Gundersen, 1993; Davanlou and Smith, 2004; Lyck et al., 2009; Garca-Amado and Prensa, 2012). Work by Friede as well as others in the 1950s rapidly confirmed Nissls suspicion and revealed that.