“To test whether a conductance increase to potassium … mediated adenosine action, the K-channel blockers, 3,4-diaminopyridine (1-100 mumol/l) or 4-aminopyridine (100-500 mumol/l) were … or Cs partially substituted for K. These substances reduced or prevented adenosine from having its depressant … on synaptic transmission.”
“When the increased excitability was counteracted by high Mg or low concentrations of tetrodotoxin, 3,4-diaminopyridine still blocked adenosine action.”