MALAGA — Scientists at the Department of Cell Biology of the University of Malaga published a study concerning morphine treatments in The Journal of Pain on July 9, 2026. The study found that activating the D4 dopamine receptor enhanced the analgesic effect of morphine and prevented the development of tolerance to it.

The research team proposes using the D4 receptor as a potential drug target for complementing morphine treatments. Alicia Rivera, a professor at the Faculty of Sciences of the University of Malaga, stated, "Our research group have been addressing the addictive aspects of morphine for more than 15 years, while its role in analgesic tolerance is a more recent line of research." The research was conducted using experimental models.

Rivera noted that prolonged administration of morphine can carry risks such as dependence, loss of efficacy, severe constipation, and decreased cardiorespiratory function. "What we have achieved is a potential way to prolong the efficacy of morphine, without having to progressively increase the dose and without increasing the risk of tolerance or pain hypersensitivity," Rivera said.

Rivera also stated that the effects are conditioned by adaptive changes in the neural circuits of the spinal cord. The 'IREM' R+D group of the University of Malaga led the study, which began in the context of Marina Ponce's doctoral thesis. Researchers from the Department of Zoology and the Department of Human Physiology of the Faculty of Medicine at the University of Malaga, along with a professor from the International University of La Rioja, participated in the study.

Mª Ángeles Real, Adrián Ruiz, Belén Gago, Iván Fatuarte, Mireya Moreno, Ismael Aranda, and Carolina Roza are listed as co-authors. The journal publication is titled "Dopamine D4 receptor activation preserves morphine analgesia and attenuates tolerance by enforcing inhibitory spinal tone in rats," with the DOI 10.1016/j.jpain.2026.106308.