ANNUAL REPORT OF THE LABORATORY OF BIOCHEMICAL GENETICS NATIONAL HEART, LUNG, AND BLOOD INSTlTUTE

Twenty-three neuroblastoma or hybrid cell lines were tested for their ability to synthesize and release acetylcholine and form synapses with rat striated muscle cells and clonal muscle cells. Six cell lines form synapses with muscle cells with high frequency; whereas, 17 cell lines were found which have defects in synapse formation. Of the 19 cell lines found that synthesize and release acetylcholfne into the.medium, six cell l,ines form synapses with high frequency, whereas three cell lines form few or no* syhapses. Rates of acetylcholine synthesis were 34-463 pmol acetylcholine/min/mg/homogenate protein; intact cells incubated with [3H]-cholin@rFoptp&ed 55-1,600 pmol [8H]-acetylcholine/mg/protein and released 80-6,J$O@ f:lol j3H]-acetylcholine /min/mg protein into the medium. Five kindsof defects were detected with cell lines that form few or no synapses: (1) little or no acetylcholine synthesis, (2) large dense core vesicles present but not clear vesicles, (3) clear vesicles present but not large dense core vesiciles, (4) little or no action potential Ca* ionophore activity, and (5) a defect in another step r required fqJt..s&.$mulus-dependent acetylcholine secretion.