The lab of Elena Gracheva is interested in somatosensation (all the sensory inputs received by the skin) and thermoregulation, and particularly how the somatosensory and thermoregulatory systems adapt to the environmental and behavioral needs of an organism. To examine these systems, her lab takes advantage of the process of hibernation in thirteen-lined ground squirrels. These tiny mammals spend about 7 months in torpor, during which they experience plummeting heart, respiratory, and overall metabolic rates. Every few weeks, the animals return to an active-like state (called interbout arousal, or IBA) for about 24-48 hours. Surprisingly, squirrels do not eat and demonstrate little interest in food during these periods despite winter-long starvation – a phenomenon known as hibernation anorexia.
Work led by Sarah Mohr (a 2019-2020 Kavli graduate student) sought to understand hibernation anorexia by comparing squirrels in the active season to squirrels during IBA periods. Her efforts showed that hibernating squirrels exhibit reversible resistance to the appetite-stimulating hormone ghrelin and reduced signaling by the satiety hormone leptin. Their findings support that this hormone sensitivity change is due to a deficiency in the thyroid hormone triiodothyronine in the hypothalamus, while thyroid function is preserved peripherally. In this study, Maryann Platt (2022 Kavli Postdoctoral Fellowship, Gracheva and Eichmann labs) confirmed that the observed ghrelin insensitivity was not due to a change in permeability of the blood-brain barrier (BBB).
In an independent project, Dr. Platt is currently deciphering how the BBB adapts to such low temperatures during hibernation, which could provide insights into possible neuroprotective strategies for therapeutic use.
This article is part of a special series highlighting the impact of the Kavli Institute for Neuroscience at Yale. The series will be published ahead of the Kavli 20th Anniversary Symposium, taking place on Friday, September 20th in TAC.