Interrogation of neuromedin U and neuromedin S release in vivo using optogenetic stimulation and mass spectrometric quantification

In order to recover large molecules, dialysis membranes with larger pores must be employed. However, larger pores allow the perfusate to leak from the probe into the surrounding tissue. One solution is to use a “push-pull” perfusion technique that minimizes the pressure across the membrane. Nonetheless, low and inconsistent recovery rates, due to the slower diffusion of large molecules and fluctuations in the pressure across the membrane in free-moving animals, remain a major obstacle. Minor pressure fluctuations that occur during sampling may cause air bubbles to form inside the tubing and probe. To overcome these problems, Takeda et al. (Neuroscience186 (2011): 110-119) developed a new microdialysis probe with a structure that allows consistent recovery of brain peptides and proteins in the awake, free-moving mouse. This microdialysis system allows rapid equalization of the pressure inside the probe with the atmospheric pressure through a “vent” hole. The result is minimal leakage and bubble formation during in vivo experiments. This system is commercialized by Eicom.
This system includes to pumps, i.e. a microsyringe pump to deliver the requested flow of perfusion fluid and a separate peristaltic pump to remove the sample from the probe. Furthermore, a rotating microdialysis cage and fraction collector are also included. Moreover, they can also provide the necessary equipment for optodialysis start-up.
Moreover, consumables for the analytical system are demanded, including columns, peptides and reagents. No funding is asked for the animals as specific funding for the generation, maintenance, validation and the neuroanatomical characterization of the NMU-Cre knockin mouse line is available.