Cyclic AMP and ultrastructural organization of the nerve cell nucleus: stimulation of nuclear microtubules and microfilaments assembly in sympathetic neurons.

As we have previously shown for electrical stimulation, in vivo cyclic AMP analogues and theophylline induce an increase (up to 8.5-fold) in the frequency of microtubular-microfilamentous inclusions in the nucleus of sympathetic neurons. These drugs, like electrical stimulation, do not modify the ultrastructural organization of such inclusions, which is briefly reviewed in the present study with the help of tilting experiments. Such data consistent with our previous opinion that microtubules and microfilaments are normal nuclear constituents of these nerve cells, their frequency being related to physiological activity. Moreover, our results may now be discussed in terms of the relationship between these nuclear inclusions and the physiological modulation of transmission through the sympathetic ganglion. Finally, as recently demonstrated in the cytoplasm, the present study shows for the first time that cyclic AMP promotes the assembly of microtubules and microfilaments in the nuclear compartment.