Changes in neutrophil met-enkephalin containing peptides in episodic cluster headache

We have previously demonstrated an increase in plasma met-enkephalin levels during the pain attacks in episodic cluster headache. The present study was undertaken in order to clarify the source of the plasma met-enkephalin increase. Recent evidence has shown that peripheral blood polymorphonuclear cells contain peptides derived from the proenkephalin A system, which can be released by specific stimuli. We studied neutrophil met-enkephalin containing peptides (NMECP) in 27 episodic cluster headache patients: 24 in a cluster period (6 of them during a pain attack), and 3 in the remission period. Neutrophil met-enkephalin containing peptide levels (after sequential enzymatic digestion with trypsin and carboxypeptidase B) were determined by radioimmunoassay with specific antiserum. Neutrophil peptide concentration (pmol/mg prot) was lower (p less than 0.01) in patients during the pain attack (14.4 +/- 0.36) than after their pain had subsided (36.7 +/- 0.31) and lower than in the remission period patients (35.8 +/- 0.4). We conclude that neutrophil met-enkephalin containing peptides decrease during pain in episodic cluster headache, and that they may be involved in the concomitant plasma met-enkephalin increase.