[Restoration of potential-dependent anti-brain antibody-inhibited calcium current by cyclic adenosine monophosphate].

A two-microelectrode voltage clamp method was used for measuring the voltage-dependent calcium current (ICa) in isolated nonidentified snail neurons. Intracellular injection of cyclic adenosine monophosphate (cAMP, 10nA, 5 min) and extracellular application of dibutyryl-cAMP (dcAMP, I mmol/l, 10-20 min) did not change the normal ICa or reversibly decreased the ICa amplitude by 10-20%. Extracellular application of antibodies against S-100 proteins resulted in a Ca2+-dependent inactivation of the ICa: the ICa amplitude dropped to 15 +/- 12% of its initial level; cAMP and dcAMP restored an amplitude of the inhibited ICa up to 50 +/- 11%. It is shown that the effect of cAMP on ICa of intact neurons depends on the cytoplasmic Ca2+-level.