Cell and explant culture of olfactory chemoreceptor cells.

An in vitro system for the study of maturation of rat and chick embryonic olfactory receptor cells is presented. A variety of dissociating agents, culture media and substrata were tried in attempts to obtain a preparation of mature living olfactory receptor cells readily visible in the microscope. Maturation was judged by the development of axons greater than 1 mm long, by the presence of cilia at the end of the dendrites and, in the rat, by the presence of immunohistochemically demonstrable olfactory marker protein, a protein present only in olfactory receptor cells. By these criteria, dissociated cells did not mature in vitro, though occasional bipolar cells with relatively short axons were seen. In explant culture, small fragments of rat tissue were positive for all 3 criteria after 6 days. In 9-day cultures, the axons had grown up to 3 mm long in both rat and chick cultures. Olfactory bulb fragments co-cultured close to the olfactory epithelium had no influence on the direction of outgrowth of axons from the olfactory receptor cells. Preliminary experiments with intracellular electrodes on the fragment cultures suggest that there are two cell types in the epithelium; one with a potential of -25 to -30 mV and, the other, -12 to -15 mV.