In animal studies the investigators have discovered a previously unrecognized effect of opioids, the reversal of long-term potentiation (LTP) at C-fibre synapses, i.e. an opioid-induced depotentiation. In principle, synaptic depotentiation may be permanent or transient. In our study the clinically used ultra-short acting MOR agonist remifentanil normalized synaptic strength after wash-out of the drug. At present it is not known whether opioid-induced depotentiation can be used to the benefit of pain patients.