| French scientists using an innovative microscopic scanning technique say they have discovered that nerve cells almost buzz with molecular agitation when they communicate with each other. The work sheds light on how cells operate at the synapse - the minute gap between neurons, as nerve cells are called. Neurons communicate by sending chemical signals across the synapse, which then latch on to specific targets, known as receptors, on the membrane of the adjoining cell. The chemicals activate an electrical signal in that cell, which then sends on a chemical signal to its neighbour, and so on down the line, eventually triggering the desired response or movement in the finger, hand, limb or other organ. Until now, little was known about receptor movement, and it was thought that these vital "locks" that open to the heart of the cell were largely static. But nanotechnology, harnessed to a video camera by French researchers, shows the receptors to be extraordinarily active and that they even move around dynamically on the membrane surface. The discovery is important, because it highlights the complex, highly mobile mechanism by which a receiving cell is able to detect just a single molecule. The team, led by Antoine Triller, head of an Inserm unit that specialises in synapse research, and Maxime Dahan, of the Kastler Brossel Laboratory at Paris's Ecole Normale Superieure, publishes its work in Friday's issue of Science, the US scientific weekly. Their observations were made on spinal cord tissue from rats, and used a probe called quantum dots - fluorescent semiconductors, with a cadmium-selenium core and a zinc sulphide shell - to tag receptors for glycine, a key synapse signalling chemical. The "dots" measure just five to 10 billionths of a metre across, and are just a quarter of the smallest nanoparticle tracers used so far. Those particles, made of gold or latex, range from 40 to 500 billionths of a metre, which means they are too big to reveal the single-molecule properties of living cells. The movement given by the fluorescing quantum dots was filmed in real time, and for long durations, using a videomicroscope. |