Ghrelin Plays a Critical Role in Blood Pressure Reduction During Torpor

Torpor (a state of reduced metabolic activity) is a fascinating physiological adaptation in many animals, characterized by significant drops in body temperature, heart rate, and crucially, blood pressure. While the overall mechanisms enabling torpor are well-studied, the precise hormonal regulators of these profound cardiovascular changes, particularly the induction of hypotension (low blood pressure), during this state are not fully understood. This study specifically aimed to elucidate the essential role of ghrelin in mediating the significant blood pressure reduction observed during torpor.

The study yielded compelling evidence that ghrelin is indeed indispensable for the characteristic blood pressure reduction during torpor. A striking difference was observed: ghrelin-deficient mice exhibited a significantly attenuated drop in blood pressure, with their systolic blood pressure decreasing by only 15-20 mmHg during torpor. In stark contrast, wild-type control mice demonstrated a robust and physiologically expected reduction of 35-40 mmHg, highlighting a 50% less effective hypotensive response in the absence of ghrelin (p<0.001). Beyond blood pressure, other cardiovascular parameters were also affected; notably, the heart rate in ghrelin-deficient animals remained approximately 20% higher throughout the torpor state, indicating broader cardiovascular dysregulation. > Crucially, the administration of exogenous ghrelin to the ghrelin-deficient mice completely rescued this deficit, restoring the typical torpor-induced blood pressure drop to an impressive 38 mmHg, a level statistically indistinguishable from that observed in wild-type controls (p<0.005). These findings unequivocally establish ghrelin as a pivotal hormonal mediator in the cardiovascular adaptations essential for successful entry into and maintenance of torpor.