On and Off Switches for Cells (image) Stanford University Medical Center Caption In the excitatory opsin (left), the red depicts a channel of negatively charged amino acids that draws positive sodium ions into the neuron to turn it on. The new bioengineered inhibitory opsin (right) is more blue to denote its channel of positively charged amino acids that draws in negative chloride ions to turn the neuron off. Credit Deisseroth lab Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.