Cyclic AMP enhances calcium-dependent potassium current inAplysia neurons

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Abstract
1. The effect on the Ca-dependent potassium current,IK(Ca), of procedures that increase intracellular cAMP levels was studied inAplysia neurons using three different pharmacological approaches. 2. Exposure to cAMP analogues which were either resistant to or protected from phosphodiesterase hydrolysis caused an increase inIK(Ca) from 30 to 50% in 10 min. The degree of reversibility of this effect varied from complete with db cAMP to very little with pcpt cAMP. 3. Exposure to cholera toxin, which stimulates the synthesis of endogenous cAMP, increasedIK(Ca) 25% in 10 min and the effect was not reversible. Both approaches were effective in all seven neuron types studied. 4. Application of serotonin plus phosphodiesterase inhibitor caused an increase inIK(Ca) in neuron R15 but not in the other neuron types. Application of pentylene tetrazole (PTZ) led to a decrease inIK(Ca). 5. It is proposed that elevation of cyclic AMP mediates an increased sensitivity of theIK(Ca) channel to Ca ions.