An ex vivo Perifusion Method for Quantitative Determination of Neuropeptide Release from Mouse Hypothalamic Explants

The hypothalamus is a primary brain area which, in mammals, regulates several physiological functions that are all related to maintaining general homeostasis, by linking the central nervous system (CNS) and the periphery. The hypothalamus itself can be considered an endocrine brain region of some sort as it hosts in its different nuclei several kinds of neuropeptide-producing and -secreting neurons. These neuropeptides have specific roles and participate in the regulation of homeostasis in general, which includes the regulation of energy metabolism, feeding behavior, water intake and body core temperature for example. As previously mentioned, in order to exert their effects, these peptides have to be produced but also, and mostly, to be secreted. In this context, it is of great importance to be able to assess how certain conditions, diseases, or treatments can actually influence the secretion of neuropeptides, thus the function of the different neuropeptidergic circuits. One method to assess this is the perifusion of hypothalamic explants followed by quantification of peptides within the collected fractions. Here, we explain step-by-step how to collect fractions during ex vivo perifusion of hypothalamic explants in which one can determine quantitatively neuropeptide/neurohormone release from these viable isolated tissues. Hypothalami perifusion has two great advantages over other existing assays: (1) it allows pharmacological manipulation to dissect out signaling mechanisms underlying release of different neuropeptides/neurohormones in the hypothalamic explants and, (2) it allows simultaneous experiments with different conditions on multiple hypothalami preparations, (3) it is, to our knowledge, the only method that permits the study of neuropeptide secretion in basal conditions and under repeated stimulations with the same hypothalami explants.