Effects of intranasal oxytocin on fear, pain and aversive memory

Oxytocin plays an important and well-known role in promoting social interaction in maternal, sexual and interpersonal behaviors. In addition, it has been increasingly linked to the modulation of pain, fear and cognitive processes such as attention and memory, which seems to be supported by the presence of oxytocin receptors in various brain areas. With this in mind, this study aims to investigate the effects of inhaled oxytocin on fear, pain perception and aversive memory in humans, as well as the relationship between them. The study involved 65 healthy female volunteers who were randomly assigned to receive either intranasal oxytocin (40 IU) or a placebo. The participants were divided into two experimental designs, A and B, with within-subject comparisons conducted. Its effects on pain were investigated by means of the Cold Pressor Test, keeping records of pain threshold and tolerance, as well as of its intensity using the Visual Analog Scale (VAS) and its classification using the McGill Pain Questionnaire. The effects on fear were investigated using the Trauma Film Paradigm, with the intensity of fear measured by means of the VAS, as well as aversion, attention and immersion in the film. A questionnaire was deployed to assess aversive declarative memory at different intervals. Intrusive aversive memories were analyzed by means of quantitative and qualitative records taken over 7 days. Our results showed that oxytocin increased dislike of pain when the painful stimulus occurred in an aversive context, which may have contributed to a negative mood state. In addition, oxytocin attenuated intrusive memories in such a way as to reduce their frequency and the suffering they caused. Altogether, the results suggest that intranasal oxytocin can modulate the subjective perception of pain, fear and aversive memory in humans, depending on the context in which the stimuli occur and their biopsychosocial relevance.