Autonomic Neurophysiology Laboratory
Description of Research
The Autonomic Neurophysiology Laboratory, hosted in Noll Laboratory, is devoted to the study of neural control of blood flow and blood pressure in health and disease.
Graduate Students: Sara Jarvis
Undergraduate Students: John Staffi, Erik Goserud
Areas of Research
Blood Pressure Regulation
Up to 500,000 Americans experience orthostatic intolerance (OI), the inability to maintain blood pressure in the upright position. Nearly 70% of Space Shuttle crew members have similar problems after spaceflight. Interestingly, the vase majority of astronauts and people in the general population who experience OI are women. We are currently conducting several investigations to help elucidate the mechanisms of OI in men and women, and to develop methods that will ameliorate OI in the general population and after spaceflight.
Cardiovascular regulation is dynamic and rhythmic; a key technique to quantify these relations is microneurographic recording of sympathetic activity in human volunteers.
What modifies our predisposition to syncope?
Does nutrition play a role in blood pressure regulation during orthostasis?
Astronauts consume fewer calories during spaceflight and return to earth with an increased risk of orthostatic intolerance. Whether a caloric deficiency modifies orthostatic responses is not understood. Having completed a 2-year investigation combining 14 days of 6° head down bedrest deconditioning with 25% caloric restriction (CR) in younger men, we show that hypocaloric intake decrease tolerance to lower body negative pressure (LBNP), independent of bedrest. Preliminary evidence suggest that CR, and the resulting decline in plasma fatty acids, may diminish the gain of sympathetic reflexes important to cardiovascular regulation.
Alternatively, obesity or caloric surfeit, and the resulting elevation in plasma fatty acids, may promote hypertension by stimulating the sympathetic nervous system. Preliminary data from our lab demonstrate augmented blood pressure, heart rate, and sympathetic nervous activity following acute elevation of fatty acids vs. placebo in healthy younger individuals.
Do women differ from men in their ability to respond to orthostatic stress?
We are currently investigating the role of blood volume distribution as a potential mechanism accounting for sex differences seen in OT between men and women. Recent findings in our laboratory have shown that women have lower splanchnic blood flow (i.e., women are more constricted in this region) at rest; however, they are less able to further constrict the splanchnic region during an orthostatic stress. Octreotide, a somatostatin analog that causes splanchnic vasoconstriction, effectively increases head-up tilt tolerance in both sexes.
A qualitative analysis of blood volume distribution
In this investigation we are seeking to locate the volume indifferent point (VIP) before and after the administration of a somatostatin analog, in order to quantify the improvement in head-up tilt tolerance observed in our previous studies. The VIP is the point, located as the vertical distance from the feet in the transverse plane, in which blood volume does not change during tilting at different tilt angles. Its location should dictate the filling gradient for the heart, therefore, a VIP that is closer to the heart should translate into better head-up tilt tolerance.
We measure bioelectrical impedance in four segments along the torso and legs during baseline (0°), 15°, 30°, and 50°.
Want to get involved?
We are looking for undergraduate and graduate students to help out as research assistants and subject volunteers. For more information, contact Sara Jarvis or call 814.865.0476