Pharmacologic responses of cells of a neuroblastoma x glioma hybrid clone and modulation of synapses between hybrid cells and mouse myotubes

Cells of the hybrid clone NG108-15 responded to 5-hydroxytryptamine (5-HT), dopamine or acetylcholine with graded depolarizations involving membrane conductance increase. Responses desensitized during continuous application of the neurotransmitters, and responses to 5-HT and dopamine cross-desensitized: a desensitizing application of one neurotransmitter also desensitized the hybrid cell to the other neurotransmitter. 5-HT and acetylcholine did not cross-desensitize. The hybrid cell 5-HT response was not attenuated by d-LSD, and was blocked by 10 −5 M morphine, although not via binding to naloxone-sensitive opiate receptors. 5-HT or the prostaglandin PGF 2α caused the release of acetylcholine at the synapses of hybrid cells with mouse myotubes. Application of 5-HT or PGF 2α also facilitated the synaptic release elecited by hybrid cell action potentials. Following treatment with the antimitotic agent cytosine arabinoside, co-cultures of hybrid cells and mouse myotubes exhibited plentiful synaptic connections only if maintained in medium containing 1 m M dibutyryl cAMP (dBcAMP). After X-irradiation, co-cultures were synaptically active even in the absence of dBcAMP. Thus, methods have been found to regulate both the short-term and long-term synaptic activity of NG108-15 hybrid cells.