Human pain treatment comes from crocodiles

Sydney University researchers have identified how crocodiles and other reptiles detect temperature - shedding new light on their adaptation to environmental changes and pointing to new pain treatments for humans.

Dr Frank Seebacher and Dr Shauna A Murray from Sydney University's School of Biological Sciences have shown that reptiles possess a family of genes that code for proteins which act as external heat sensors as well as providing an internal thermometer. These proteins, 'transient receptor potential ion channels', are closely linked with sensory nerves at the animal's surface as well as in their liver, heart and muscles.

According to the researchers, information about internal temperatures and environmental conditions is fed back to the brain via these receptors. The brain is then able to direct the behaviour of the animal depending on how warm or cold it is relative to the environment.

"Until now it was unknown exactly how cold-blooded (ectothermic) animals sensed heat in their environment, which is an important step in our understanding of the biological functions governing an animal's ability to regulate their body temperature," said Seebacher.

"This capacity to sense environmental and internal temperatures is a prerequisite for the evolution of the kind of thermal regulation we find in warm-bodied (endothermic) animals, such as ourselves.

"The functioning of all organisms depends on temperature, and we as humans know very well that when our body temperature deviates by only 3°C from normal we are in serious trouble. Other animals are more tolerant, but must still regulate their body temperature so that their cells and organs can function effectively," said Seebacher.

"Interestingly, similar proteins exist in mammals where among other things they are responsible for "tasting' the heat in chillies. Hence, the detection of environmental heat and "hot' chillies depends on the same mechanism, and both are closely linked to perception of pain."

"Transient receptor potential ion channels are therefore of enormous interest to medicine because they could be the target for new pain relieving drugs."