Kisspeptin Synaptic Input to POMC Neurons

Oregon Health & Science University, Portland OR

Investigators

Abstract

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to understand the role of kisspeptin in the regulation of energy homeostasis through its modulation of hypothalamic anorexigenic neurons that control food intake and energy expenditure. Abnormalities in the central signaling of peripheral metabolic cues such as leptin and insulin have led to disorders in energy homeostasis such as the metabolic syndrome and anorexia-cachexia. Pro- opiomelanocortin (POMC) neurons play a critical role in energy homeostasis and mediate, at least in part, the central signaling of these two metabolic hormones. In addition, kisspeptin neurons have been shown to express leptin and insulin receptors, and kisspeptin administration directly stimulates POMC neurons. Therefore, kisspeptin neurons may play an integral role in the control of energy homeostasis through their synaptic input to POMC neurons. The central hypothesis of this proposal is that arcuate kisspeptin neurons, also known as KNDy (kisspeptin/neurokinin B/dynorphin) neurons, directly excite POMC cells in the arcuate nucleus through activation of canonical transient receptor potential (TRPC) channels, and this excitation is reduced in the fasted state. To address this hypothesis, I have designed two specific aims, which include a creative combination of transgenic and optogenetic tools in conjunction with molecular biology (aim 1) and electrophysiology (aim 2). In aim 1, I will elucidate the kisspeptin signalng components in POMC neurons of fed and food restricted POMC-EGFP male mice by dispersing and harvesting pools of POMC neurons for quantitative PCR analysis. Our lab has been in the forefront in the development and implementation of this technique, which gives us an extremely powerful tool to characterize signaling molecules (e.g., receptors and ion channels) in neurons. In aim 2, I will interrogate the functional connection between KNDy neurons and POMC neurons in the arcuate nucleus by using the innovative tool of optogenetics to selectively photoactivate KNDy neurons while simultaneously recording from arcuate POMC neurons. By using selective antagonists I will determine if the kisspeptin-induced activation of POMC neurons occurs via TRPC channels, as we have shown for kisspeptin-induced activation of other hypothalamic neurons (i.e., GnRH neurons). Together, the investigation of the gene expression and cellular pathways specific to th functional connectivity between KNDy and POMC neurons will help identify cellular targets for therapeutic interventions to counteract disorders associated with energy homeostasis.