Q: " I have some Gi-DREADDs that I got from UNC and am preparing to inject an aliquot of them into the cortex. Can you tell me if the sample I got from UNC should be diluted or should it be used as is? If diluted, what do you recommend and how much?" A1: " We look at the titer and generally inject 10^9/uL--so it may need to be diluted to 10^9/ul" Explanation: we try to inject virus with a titer generally ~ 10^9/ul A2: " It depends on what kind of experiments you are going to do. Some experiments you need to dilute the virus just like Bryan said. Some are not. You can aliquot the virus into 5ul/tube after thawing the virus on ice, and store it in -80. Try your injection with different dilutions of virus. Check the expression and then decide what dilution is good for you. "