The Journal of Neuroscience, October 31, 2007, 27(44):11934-11939; doi:10.1523/JNEUROSCI.3330-07.2007
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Brief Communications
Opioid-Mediated Placebo Responses Boost Pain Endurance and Physical Performance: Is It Doping in Sport Competitions?
Fabrizio Benedetti,
Antonella Pollo, and
Luana Colloca
Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, 10125 Turin, Italy
Correspondence should be addressed to Fabrizio Benedetti, Dipartimento di Neuroscienze, Università di Torino, Corso Raffaello 30, 10125 Torino, Italy. Email: fabrizio.benedetti{at}unito.it
The neurobiological investigation of the placebo effect has shown that placebos can activate the endogenous opioid systems in some conditions. So far, the impact of this finding has been within the context of the clinical setting. Here we present an experiment that simulates a sport competition, a situation in which opioids are considered to be illegal drugs. After repeated administrations of morphine in the precompetition training phase, its replacement with a placebo on the day of competition induced an opioid-mediated increase of pain endurance and physical performance, although no illegal drug was administered. The placebo analgesic responses were obtained after two morphine administrations that were separated as long as 1 week from each other. These long time intervals indicate that the pharmacological conditioning procedure has long-lasting effects and that opioid-mediated placebo responses may have practical implications and applications. For example, in the context of the present sport simulation, athletes can be preconditioned with morphine and then a placebo can be given just before competition, thus avoiding administration of the illegal drug on the competition day. However, these morphine-like effects of placebos raise the important question whether opioid-mediated placebo responses are ethically acceptable in sport competitions or whether they have to be considered a doping procedure in all respects.
Key words: placebo; pain; opioids; conditioning; sport; doping
Received July 23, 2007;
revised Sept. 20, 2007;
accepted Sept. 20, 2007.
Correspondence should be addressed to Fabrizio Benedetti, Dipartimento di Neuroscienze, Università di Torino, Corso Raffaello 30, 10125 Torino, Italy. Email: fabrizio.benedetti{at}unito.it