Optimizing techniques for injecting DiI into the brain nuclei of neonatal mice P6 - C57Bl6/CBA

Abstract DiI (1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate) is a lipophilic dye used to research the intracerebral connections of neonatal animals. This dye is most frequently used in the form of dry crystals, but injections of the marker in this state into the mouse brain nuclei, such as MHb (2 cases), LHbM (2 cases), LPA (3 cases) and TS (1 case), clearly revealed excessive lateral diffusion marker into the tissue. Eventually, all the investigated cases except the LPA gave a false positive result. To find the optimal method of marker injection,DiI-kerosene liquid films (3 cases in the MHb); DiI-kerosene gelatinous paste (3 cases in the MHb); injections of insoluble DiI crystals from a solution of 99% dmso (3 cases in the MHb) and 70% ethanol (3 cases in the MHb, 2 cases in the LHbM, 4 cases in the TS) were tested. Injections of DiI in the form of undissolved crystals from a 70% ethanol solution gave a minimal level of side diffusion in all the studied cases. This method of injection is optimal and recommended for use.