A new study suggests that a form of marijuana that occurs naturally in our lungs may hold the key to fighting all kinds of coughs.

An international research team reports the marijuana-related chemical in our lungs controls how our airways expand and contract. They say the findings could lead to new treatments for a variety of respiratory problems, without the addictive qualities of marijuana or codeine, a traditional cough treatment.

Scientific studies from the 1970s had shown that delta-9-tetrahydrocannabinol -- the active ingredient in marijuana -- improved chronic asthma symptoms for some patients but worsened symptoms in others. Why this happened remained a puzzle until publication of the study in the Nov. 2 issue of Nature.

Senior author Daniele Piomelli, a professor of pharmacology at the University of California at Irvine, says the researcher found that rats and guinea pigs have a chemical called anandamide, which is similar to marijuana's active ingredient, that causes the dual effect.

Anandamide locks onto the surface of lung muscle cells and controls how the lungs respond to various chemical agents that trigger dry coughing. Piomelli found anandamide's influence depends on how much the lungs already are contracted.

For example, if the lungs were already tense, anandamide relaxed them. Yet if the airways were relaxed, the chemical triggered lung constriction. While seeming paradoxical, Piomelli says anandamide's true function may be as a regulatory mechanism.

"What we want with our muscles is not for them to be completely relaxed or completely contracted. We want them to be always at a certain level of contraction, ready to go further up or further down," Piomelli says. Anandamide may control that balance.

To test that theory, the researchers severed the vagus nerve, which keeps lung muscles contracted to a certain tone, relaxing the lung. When anandamide was given to these animals, the lungs contracted again, while it had no effect on animals with an intact vagus nerve.

"It looks like it's some sort of compensatory factor," says Piomelli.

Piomelli says the findings could lead to new treatments for chronic cough, asthma, hay fever, certain cancers and chronic obstructive pulmonary disease. In animals with a cough produced by capsaicin, the active ingredient in red pepper, giving anandamide orally stopped the cough.

"There are receptors within the mucosa that recognize these irritants like capsaicin, and those receptors also seem to recognize anandamide," says Eric Barker, an assistant professor of medicinal chemistry and molecular pharmacology at Purdue University. "So in terms of pharmacology, there's clearly some overlap there. It seems that [the researchers] are able to block bronchospasm or the irritation that occurs from capsaicin with anandamide."

Piomelli says anandamide shows promise as an alternative to current cough treatments.

"Codeine, the mother of all cough suppressants, acts on the cough center in the brain," says Piomelli. "Because it's a central effect, codeine, which is basically a derivative of morphine "produces sedation, respiratory depression -- you can even die of codeine intoxication."

However, since anandamide acts on nerves in the trachea and lungs and is quickly eliminated from the body, an inhaler could potentially control the cough without any side effects, Piomelli says.

(From HealthScout)