02:16 PM ET 09/23/98 Synthetic marijuana-like drug eases pain - study By Patricia Reaney LONDON, Sept 23 - American researchers have shown that a synthetic drug that mimics the main active ingredient in marijuana works like morphine to reduce pain, they said on Wednesday. In a letter to the science journal Nature, Dr Ian Meng and researchers from the University of California in San Francisco explained how compounds in marijuana, known as cannabinoids, affect cells in an area of the brain that controls pain. Marijuana has been touted as a pain killer for a variety of medical conditions but studies of humans have produced inconsistent results and its use for medicinal purposes is still controversial. Meng's finding from his research on rats raises the possibility that marijuana-like drugs could be used to treat pain. ``These results indicate that the marijuana-like drug can reduce pain by affecting the same pain modulating neurons (brain cells) as morphine, but through separate mechanisms,'' Meng said. Unlike morphine and other opiates which can cause nausea and respiratory depression, marijuana increases appetite without uncomfortable or serious side effects. The addiction potential of marijuana is also much lower. ``The implications for future development or treatment would be looking at different combinations of therapies, a lower dose of morphine combined with a low dose of cannabinoid,'' Meng said in a telephone interview. ``Perhaps you could eliminate the nausea or at least reduce it and increase the pain-killing effects,'' he added. The research is the latest study into the medicinal properties of marijuana. It follows a report by the National Institute of Mental Health in the United States in July that showed cannabinoids could protect the brain from the damage caused by injuries and stroke. Meng and his colleagues tested the effects of the synthetic drug on a region of the brain called the rostral ventromedial medulla (RVM). By measuring the time it took for rats to move their tails away from a heat source they showed the pain-relieving effects of cannabinoids. Rats given the drug kept their tails on the heat much longer than rats which didn't receive it. In a second experiment the researchers tested the effect of the drug on the neurons in the RVM of anesthetized rats and found it produced the same changes as morphine, but in a different way. Some sufferers of arthritis have used marijuana to relieve their symptoms. Cancer patients also claim it alleviates the nausea from chemotherapy treatments and medical evidence has shown it increases the appetite of AIDS sufferers with wasting diseases.