Pain Therapy – Extra Hot

22. July 2008

The Hungarian pharmacologist Nikolaus Jancso was one of the first to isolate Capsaicin the hot substance from chili and paprika to experiment with it. He set the basis for Capsaicin research with it in medicine at the University of Graz/Austria among others. But lately the pain therapy with the chilli extract sustains bitter setbacks.

Capsaicin as the alert system of the stomach mucosal lining

The conclusion that only nozi-receptors, i. e. pain conducting nerve fibers, are stimulated by Capsaicin goes back to Jancso’s account as well. That was back in the early eighties. Since then, researchers count on the promising possible applications of the active ingredient in pain therapy. Professor Dr. Peter Holzer, head of the research unit for translational neurogastroenterology at the Institute of Experimental and Clinical Pharmacology
of the Medical University Graz, deals with Capsaicin for the past three decades. In the eighties he and his team were able to identify sensitive respectively noziceptive nerve fibers as an important alert system of the stomach mucosal lining. This discovery was possible due to Capsaicin. DocCheck spoke with the Professor in Graz/Austria.

Capsaicin defends the stomach against damaging material

According to Holzer the study of the alert system is very important since it must be assumed that a dysfunction might lead to gastritis and ulcer, especially in older age. The pharmacologist pits on strengthening of the defence mechanism with drugs. Experimental studies at the Graz institute had shown that Capsaicin strengthens the resistance respectively the defence mechanism against aspirin, alcohol or acids. A study in Singapore where people were treated with chilli extract came up with the same results. The protective results come from the stimulation of the pain- and acid sensors with Capsaicin. This increases the blood flow in the stomach and activates local protective mechanisms.

Capsaicin-receptor as a weapon against pain

In an initial large wave of research, scientists learned that Capsaicin-sensitive nerves are essential for inflammation pain. In many cases gastritis and ulcer come along with indisposition and pain. The same symptoms might appear in case of functional dyspepsia as well. Just how the stomach ache develops is mostly unknown.
But in the late nineties when they nailed down the capsaicin-receptor called TRPV1 everybody talked about a quantum jump in pain therapy. The receptors are located in all those places where pains might develop such as for example in the skin, the muscles, the heart or the stomach and intestines. It is a very important sensor, says Holzer, transmitting the pain caused by heat or acid. But is appears to be a whole lot more complex than assumed before which was confirmed by recent research results.

Problems with the switched-off pain-receptors

During a second wave of research many antagonists were developed to switch off the function of TRPV1 receptors. Thus chronic inflammatory pains can be relieved, explains Holzer. Researchers observed earlier that painful skin diseases like pruritus and zoster improve after a temporary elimination of Capsaicin sensitive nerves. But this is always a matter of symptomatic treatment, as the pharmacologist reports, meaning that the root remains, only the pain perception is being suppressed. And since the protective mechanism which for example stimulates the blood flow in the stomach, is crippled as well – the question appears just how desirable this therapy actually is.

Another unsolved problem was discovered last year. During phase-I studies, the body temperature of some of the test persons went up to 40 degrees Celsius. The Professor in Graz explains that the reactions are very individual: "The challenge of all TRPV1 antagonists is to find a way to switch off the unwanted functions of the Capsaicin receptors (pain), but at the same time to obtain the desired functions (protection of the mucous membrane, regulation of the temperature). The preliminary findings are overall helpful for a better understanding of the coherences of pain transmittance. But in research of pain therapies you have to proceed a lot more subtle and differentiated." From his point of view it will take at least five more years until antagonists without any serious side effects will be available.

Putting a questions mark over the selectivity of capsaicin
Pain research just recently was put into its place again by researchers at the Brown University in Rhode Island/USA. Helen Gibson and Julie Kauer and their team found out that the TRPV1 receptor does not only register pain but is also involved in storing memories. During tests with rodents it showed that switching off the receptor influences the generation of memory. Here looms a considerable demand for research.

Here’s to all chilli fans out there – hot is healthy! And according to Holzer it even improves the protective mechanism of the stomach mucosa.

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