Extracellular levels of ATP and acetylcholine during lithium-pilocarpine induced status epilepticus in rats

• Extracellular levels of ATP and acetylcholine were measured in rat hippocampus.
• ATP release is reduced by calcium-free conditions, but not by neostigmine or tetrodotoxin.
• Status epilepticus leads to an increase of extracellular ATP which is only measurable when 5′-endonucleotidase is inhibited.
• There was no evidence of crosstalk between acetylcholine and ATP.

Acetylcholine (ACh) and ATP are rapidly acting neurotransmitters with a putative role in epileptic seizures. In the present study we investigated extracellular concentrations of both neurotransmitters in parallel by microdialysis in rat hippocampus. We found that infusion of neostigmine increases, while calcium-free perfusion and infusion of tetrodotoxin (TTX) decreases, ACh levels. Calcium-free perfusion also decreased ATP levels which were, however, not affected by neostigmine or TTX. During status epilepticus, ACh levels were increased threefold but returned to baseline after the termination of seizures by diazepam. ATP levels were unchanged during status epilepticus but a several-fold increase was seen when AOPCP, an inhibitor of 5′-endonucleotidase, was infused. The results demonstrate an increase of ATP levels during epileptic seizures which, however, was not of neuronal origin.