High-dose adenosine infusion provokes oscillations of chest pain without correlation to opioid modulation: a...

Adenosine is a neuromodulator with both excitatory and inhibitory effects in different organs. High-dose adenosine infusion provokes chest pain in patients and healthy volunteers. This study examines the nature of chest pain and whether it is modified by the mu opioid receptor agonist (beta-endorphin) or a nonselective opioid antagonist (naloxone). Ten healthy volunteers with a mean age of 26 +/- 3 years participated in the study. The study was performed during 3 sessions. During every session the subjects were given a high dose of adenosine infusion (140 microg/kg/min) for 22 minutes. After 5 minutes, the subjects were randomized in a double-blind order on 1 of the 3 categories: (1) as placebo, NaCl bolus for 2 minutes followed by NaCl infusion for 15 minutes; (2) beta-endorphin bolus followed by infusion; and (3) naloxone bolus followed by NaCl infusion. Hemodynamic and pain parameters were monitored. During adenosine infusion, all volunteers experienced chest pain with oscillations of pain intensity. The oscillations continued during beta-endorphin and naloxone. There were no significant differences between hemodynamic and pain parameters during beta-endorphin or naloxone compared to adenosine infusion. High-dose infusion of adenosine provokes chest pain with oscillations of algesia and pain-free intervals. Peripheral opioid administration did not influence the adenosine-provoked chest pain.

Adenosine-induced oscillations of pain and pain-free intervals could theoretically be a sign of neuronal reflex activity dependent on spatiotemporal summation of adenosine excitatory and inhibitory properties. This could contribute to the complex nature of angina pectoris. Peripheral opioid receptors might not be involved in the oscillations.