Apparently, in this experiment they did not use actual opioid drugs but instead used a placebo protocol (to avoid side effects), but they did produce the empathy reduction effect. And this effect was cancelled out by giving the test subjects naltrexone, so it does seem to be dependent on the opioid receptors.
Apparently, in this experiment they did not use actual opioid drugs but instead used a placebo protocol (to avoid side effects), but they did produce the empathy reduction effect. And this effect was cancelled out by giving the test subjects naltrexone, so it does seem to be dependent on the opioid receptors.