Maintenance of glucose homeostasis is essential for health, and is tightly regulated by peripheral and central counter-regulatory mechanisms. The mechanisms underlying central counter-regulation are not fully understood, although the hypothalamus is thought to play a key role. Corticotrophin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVH) regulate cortisol release via the pituitary-adrenal axis and may also project to the autonomic nervous system, although this has not been definitively established(1). In addition, although glucose-sensitivity has been shown for uncharacterized PVH neurons in the rat, it is unclear whether CRH neurons contribute to hypothalamic glucose sensing(2). We used a genetically modified mouse strain expressing TdTomato under the control of the CRH promotor(3) to identify CRH neurons. After terminal anaesthesia with isoflurane, hypothalamic slices were cut in 10mM glucose for recordings of CRH neuronal properties and sensitivity to glucose levels. Data is presented as mean±S.E.M., unpaired t-test. Whole cell recordings (n=68 CRH neurons) revealed two distinct populations: group 1 (n=59) fired spontaneous action potentials in 10mM glucose (7.3±0.67 Hz,), whilst group 2 were silent under the same conditions (n=9). Group 2 also had lower input resistance (385±63 vs 753±51 MΩ, p<0.0001) and larger cell capacitances (51.1±6.4 vs 30.4±2.8 pF, p<0.001). We observed heterogeneous responses to a glucose step from 10 to 2.5mM. Of the group 1 population, 8/23 neurons showed a reversible fall in firing frequency (glucose excited) and a further 2/23 neurons showed an increase (glucose inhibited). All of the group 2 neurons tested were depolarised by the step, indicating glucose-induced inhibition (n=4). Recordings in the presence of TTX to block synaptic inputs suggest many CRH neurons (7/11) are also intrinsically glucose inhibited, depolarising by 7.5±1.2mV on stepping to 2.5mM glucose. The group 2 neurons were located in more caudal and ventral parts of the PVH, areas associated with autonomic projecting neurons(4). To establish whether PVN CRH neurons project to brainstem autonomic control centres we stereotaxically injected a canine adenoviral vector(5) into the nucleus of the solitary tract/dorsal vagal motor nucleus complex (recovery surgery performed under ketamine 70mg/kg and medetomidine 0.5mg/kg i.p anaesthesia, n=2). This enabled retrograde tracing to the PVH and revealed the presence of CRH neurons with brainstem projection in the caudal region (11-13% of the autonomic projecting neurons co-localised with TdTomato, range). These data indicate that subpopulations of CRH neurons are glucose sensitive and have the necessary anatomical connectivity to play a role in the counter-regulatory response to hypoglycaemia.