Defining pain as a concept is very difficult. Pain is a very important protective mechanism of the body. A widely accepted definition of pain is that drafted by the International Association for the Study of Pain (IASP) and accepted by the American Pain Society and World Health Organization: “Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage”.

Pain transmission starts when tissue is damaged after being exposed to:

  1. Chemical
  2. Mechanical
  3. Thermal noxious stimuli.

After this the nociceptors are activated.syn

Although pain is a protective mechanism, it is a very unpleasant event in the patient’s life, sometimes affecting very much his lifestyle. The “treatment” of pain is made by a class of drugs called analgesics.

The most potent group of analgesics are the opioid drugs. These drugs act on the μ opioid receptor (MOR). Using these drugs chronically or in high doses has side effects: respiratory depression, nausea, constipation, hypotension, urinary retention and one of the biggest problems is that are very addictive drugs.

Our organism produces a group of substances called the endogenous opioids, called endomorphin. Endomorphins help to biologically regulate and moderate pain. Endomorphins are tetrapeptides and this group is subdivided in: endomorphines -1 and endomorphines-2.

For many years it hasn’t been possible to produce these substances in laboratory, largely due to their specific linear structure, which makes them unstable.

In a recent experiment a group of scientists from Tulane University has produced endomorphin variants. These endomorphin variants have improved stability and solubility thanks to their ring structure.

During the experiment was observed that rat’s breathing was not disrupted by endomorphines. Additionally was observed that endomorphines showed antinociceptive effects in rats that were tolerant to morphine.  The team of scientists concluded that at doses giving equal (or even greater) antinociception than morphine in rat, these analog drugs reduced:

  1. Respiratory depression
  2. Impairment of motor coordination
  3. Tolerance and hyperalgesia

These results suggest that this group of drugs can be the new gold standard pain relief, but further studies are needed to test if these drugs have any possible side effects.