Are pain and pleasure receptors the same

Single receptor blockers can turn pain into pleasure

Linköping / Innsbruck - Pleasant and unpleasant perceptions are processed in the brain by the same hormone docking point - and this has decisive consequences for well-being in the experiment, as the Austrian psychologist Michael Fritz has now found out using the example of mice. If this receptor was blocked, the rodents no longer perceived fever, pain and nausea as negative, for some these experiences might even have felt good.

The results hold opportunities for new therapeutic paths. For example, these docking points could be covered with certain active ingredients and thus relieved the chronically ill from malaise.

Fritz, who works at Linköping University in Sweden, and colleagues used genetic manipulation to prevent the formation of the melanocortin-4 receptor (MC4R) in mice. In contrast to their unaltered conspecifics, animals treated in this way were not deterred by a chamber in which they were confronted with some unpleasant substances: bacteria that cause fever, nausea-inducing solutions and active substances that negatively affect their mood. The experiment even showed - on the contrary - that the mice without this hormone docking site could be found there more often than in another chamber, where they had nothing to fear.

Positive pain perception

The researchers obtained the same results after nasal administration of an active ingredient that blocks MC4R. Animals treated in this way did not care much, even pain. The researchers found that pain, nausea and fever in these animals did not lead to a decrease in the amount of the "happiness hormone" dopamine, as in normal mice, but that it actually increased in a certain brain region (nucleus arcuatus). "As a result, the animals perceive things like nausea, infections or internal stress as positive," explained Fritz.

"The brain has developed a nerve connection in which both positive and negative perceptions are processed under the control of a single type of receptor," says the native Tyrolean. Possibly this was important in evolution in order to quickly change the perception of certain environmental stimuli if necessary, the scientists write in the journal "The Journal of Clinical Investigation".

New solutions for the chronically ill

The discovery also has clinical relevance. In patients with chronic inflammatory diseases, the level of suffering caused by malaise is very great, leads to a loss of motivation and increases the risk of depression as a side effect. It may be possible in the future to alleviate this with a simple nasal spray that contains melanocortin-4 receptor blockers. (red, APA, July 31, 2018)