Direct measurement of the release of ATP and its major metabolites from the nerve fibres of the guinea-pig taenia coli.

1. The release of adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate and adenosine from guinea-pig taenia coli in response to electrical stimulation of intramural nerves was measured directly using high performance liquid chromatography separation and fluorometric detection. 2. Purines were released in a frequency-dependent manner by trains of transmural electrical pulses at 1-30 Hz. 3. Electrically evoked release of ATP was abolished by tetrodotoxin (10(-6)mol/L) but was not affected by nicardipine (10(-6)mol/L). 4. The release of purines was reduced in the presence of atropine. 5. Pituitary adenylyl cyclase-activating peptide did not evoke the release of any purines and did not modify the electrically evoked release of purines. 6. The results suggest that ATP and its major metabolites are released from a neuronal source, possibly the enteric inhibitory nerves, in the guinea-pig taenia coli.