Fig. 1.

α7 subunit transcript levels increase during preganglionic and postganglionic synapse formation and then plateau in embryonic CG neurons in situ. Absolute amounts of α7 subunit mRNAs were measured in individual ganglia at landmark stages of synaptogenesis by using quantitative RT-PCR with a mutated α7 cRNA internal standard. Values are normalized to the number of transcript copies per neuron to account for developmental changes in neuron number. Each value represents the mean ± SEM of the number of separate determinations indicated for each time point. For comparison, synaptic α3 subunit mRNA levels were measured at three key stages of preganglionic and postganglionic synapse formation. α7 transcript levels increase ninefold from E5 to E15 and are twofold greater than α3 mRNA levels at all stages of synaptogenesis examined.