Project Summary/Abstract The Electrophysiology Core will provide centralized services for electrophysiological studies, including preparation of in vitro brain slices, patch-clamp recordings, immunohistochemistry, and the associated data analysis. Project 1 (Saper), Project 2 (Scammell) and Project 4 (Chamberlin) will use this Core facility. We will use patch- clamp recordings and channelrhodopsin2 (ChR2)-assisted circuit mapping (CRACM) to determine, for Project 1, functional synaptic connectivity between CGRP expressing neurons of the external lateral parabrachial nucleus (PBel) and neurons of the basal forebrain (BF), lateral hypothalamus (LH), supramammillary nucleus (SUM) and central amygdala (CeA). For Project 2 we will determine functional synaptic connectivity between cholinergic, glutamatergic and GABAergic neurons of the laterodorsal and pedunculopontine tegmental nuclei (LDT/PPT) and neurons of the BF, midline thalamus and SUM, and for Project 4 between glutamatergic premotorneurons of the parahypoglossal zone and hypoglossal motoneurons. In these experiments we will define the neurotransmitters and postsynaptic receptors involved in these inputs. In addition, the Core will be continuing the validation and optimization of the stimulation paradigms for the opto-genetic and pharmaco-genetic tools (ChR2 and ArchT excitatory and inhibitory DREADDs) used by these Projects. The Projects will benefit from the expertise and shared resources of the Core.