Excitability and chemosensitivity properties of a somatic cell hybrid between mouse neuroblastoma and sympathetic ganglion cells

A somatic cell hybrid line, NX-31, formed by fusion of mouse neuroblastoma and mouse sympathetic ganglion cells has been studied for its electrophysiologic properties and its chemosensitivity to iontophoretically applied acetylcholine (ACh). The cell lines (parent and hybrid) were treated and studied in media containing mM dibutyryl cyclic AMP (db-cAMP) in order to obtain them in a maximally differentiated state. The hybrid cell line was electrically excitable and its excitability characteristics were found to be closer to those of its putative neuronal parent than were those of its neuroblastoma parent. In particular, increases were observed in the percentage of cells giving action potentials when electrically stimulated at their resting membrane potentials, in the maximal rate of rise (dV/dt) of the elicited spikes, and in the percentage of cells displaying repetitive-firing ability. Fifty percent of the hybrid cells were sensitive to ACh. Two types of depolarizing responses were evoked—an early, rapidly developing response and, less frequently, a late, slowly developing response. The first type of depolarization appears to be mediated by a nicotinic cholinergic receptor while the latter type does not. Neuroblastoma cells may exhibit only the early, rapid response; sympathetic neurons show depolarizations corresponding to both types of responses. These findings suggest that the phenotypes expressed by NX-31 hybrid cells more closely resemble those of sympathetic neurons than do those of their neuroblastoma parents. The possibility is raised of further exploiting the strategy of hybridizing a dividing cell line with other types of neurons to obtain new neuronal cell lines.