[Effect of intracellular injection of cyclic adenosine monophosphate on the calcium current in identified snail neurons].

The effect of intracellular cyclic adenosine monophosphate (cAMP) injection and extracellular theophylline application on calcium current were investigated in Helix RPa3 and LPa3 neurons. It was found that iontophoretic cAMP injection (current 10-35 nA, duration about 1 min) caused a decrease in the amplitude of calcium current which restored to the initial level following the cessation of injection. Its current-voltage characteristic was not displaced along the potential axis in the presence of cAMP injection indicating that the calcium current decrease was due to the fall of maximum calcium conductance. Extracellular theophylline application in concentration of 1 mM/1 caused a decrease in the calcium current amplitude by 50-75% from the initial level. The hypothesis is discussed about the participation of cytoplasmic factors in regulation of calcium current in mollusc neurons.