Endogenous oxytocin release helps the mind to deal with pain

Basic research in rats showed that the endogenous release of oxytocin altered the perception and evaluation of pain, but did not induce physical analgesia.

The hypothalamic neuropeptide oxytocin exerts not only prominent pro-social and anxiolytic effects but also has a role in pain processing. PhD student Stephanie Küppers (Central Institute of Mental Health Mannheim, Germany) aimed to get more insight into the mechanisms by which oxytocin is involved in the alleviation of pain perception [1].

In a transgenic rat model, Ms Küppers demonstrated the presence of projections of oxytocin neurons –originating in the paraventricular and the supraoptic nucleus– to the anterior insular cortex. Because the anterior insular cortex integrates pain processing and emotional valence, this brain area is considered a target structure for oxytocin action in pain conditions.

Next, using chemogenetic stimulation of local axonal oxytocin release and conditioned place preference, Ms Küppers showed that oxytocin release in the anterior insular cortex alleviated pain perception behaviour in the rat model. Interestingly, local oxytocin release in the anterior insular cortex did not decrease the physical pain stimulus. It was the altered perception of the pain that changed the behaviour of the rats.

In another experiment, rats were presented with the choice to self-administer a sugar solution paired with a light foot-shock in an operant conditioning setup. In line with the conditioned place-preference-test results, evoked local oxytocin release doubled lever pressing behaviour despite the simultaneously delivered electric shocks. In other words, oxytocin release increased the willingness to endure pain.

Altogether, these results suggest that endogenous oxytocin release alters the perception and evaluation of pain, but does not induce physical analgesia. “Because it is known that endogenous oxytocin release can be induced by social touch, these results suggest that it is important to hold hands or hug a person whenever they are going through a painful event,” concluded Ms Küppers.

1. Küppers S, et al. Oxytocin improves positive emotional valence to painful stimuli via action in the insular cortex. Abstract S10.03, ECNP Congress 2022, Vienna, 15–18 October, Austria.

 

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Posted on 28 November, 2022