SELECTIVE DOWN-REGULATION OF AN INACTIVATING K-CELLS( CONDUCTANCE BY ANALOGS OF CAMP IN MOUSE SCHWANN)

1. Voltage-dependent K+ conductances on Schwann cells in organotypic c ultures of mouse dorsal root ganglia were classified as inactivating o r sustained (responsible for currents I-A and I-K, respectively). I-A is known to be much reduced on Schwann cells that contact neurites. 2. In the absence of neurones, I-A and I-K were present. I-A, but not I- K, was markedly reduced (by 80% after 105 h of treatment) by 2 mM 8-(4 -chlorophenylthio)-cAMP (cpt-cAMP), a weakly hydrolysable analogue of cAMP. The effect did not appear for at least 2 h and was maximal after about 100 h. 3. The effect of 1 mM cpt-cAMP was abolished in the pres ence of an inhibitor of protein kinases, mocinnamyl(amino)ethyl]-5-iso quinolinesulphonamide (H-89, 10 mu M) 4. Other analogues of cAMP, but not an analogue of cGMP (8-bromo-cGMP), also reduced I-A. 5. We conclu de that I-A, but not I-K, can be downregulated by activation of the pr otein kinase A pathway.