Distance of target search of isolated rat hippocampal neuron is about 150 mu m

Although the survival of neuronal cells is highly dependent on neural conne ctions with afferents or targets,(10,14,15) little is known about the survi val of immature neurons that have not yet encountered the partners. Herein, using cultures of isolated hippocampal neurons of rat embryos, we have att empted to elucidate the contribution of neurite outgrowth to neuron surviva l and found that neurons died at a certain degree of neurite length with ap optotic characteristics in cases of no contact with other neurons, The thre shold was 143.4 mu m, which was about five times as long as the cell body d iameter. It was altered by depolarization or in the presence of basic fibro blast growth factor. Thus, neurons may be designed to kill themselves if th ey cannot find their targets after exploration within a particular area, th e extent of which is variable due to cellular conditions. (C) 2000 IBRO. Pu blished by Elsevier Science Ltd.