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THE poison from the spurs of the duck-billed platypus could point to ways of
designing new types of painkiller, physiologists say. They believe that a toxin
in the poison acts directly on our pain receptors.

The male of this strange Australian species has spurs on its hind legs that
contain at least four different toxins. They are thought to help the animals
defend their breeding territory. 鈥淚t鈥檚 an unusual venom that鈥檚 not designed to
kill or paralyse its victims,鈥� says Rosemary Martin of the Australian National
University in Canberra. Humans that are pricked by the platypus experience
intense pain that can sometimes last for several weeks, she adds. 鈥淚t seems
designed as a deterrent to induce pain.鈥�

Martin and her colleagues, led by Greg de Plater, have now pinned down how at
least one component of the poison of the platypus鈥檚 spurs behaves. The
researchers tested the effects of a protein in the toxin on the neurons of
laboratory mice. It turned out that the protein binds to a channel in the
membranes of the neurons which allows positive ions to enter and leave the
cells.

The researchers say that these channels are also activated when we feel pain.
鈥淭his is an example of a natural toxin acting directly on pain receptors,鈥� says
de Plater, who reported the results at a meeting of the Physiology Society in
Cambridge last month. 鈥淭hat has never been found in a venom before.鈥�

De Plater and the team suspect that the molecules which normally activate
pain in the body might be chemically similar to the toxin protein. This may be
the key to finding new painkillers. 鈥淚f you could find agents that inhibit this
toxin, then it鈥檚 not inconceivable they could be developed into analgesics,鈥�
says Rod Scott, an electrophysiologist at the University of Aberdeen.