Hydrogen Sulfide Decreases Blood Pressure by Influencing the Excitability of Area Postrema Neurons

Abstract

Hydrogen sulfide (H2S), an endogenous gaseous transmitter, has been shown to act in the central nervous system (CNS) to influence cardiovascular (CV) function. Microinjection of H2S into central autonomic control centers such as the paraventricular nucleus and subfornical organ has been shown to increase blood pressure (BP) and electrophysiological studies have demonstrated that H2S depolarizes neurons in these same regions. Depolarizing effects of H2S have also been demonstrated in the nucleus tractus solitarius, a medullary autonomic control center with reciprocal connections to the immediately adjacent area postrema (AP). The AP is a circumventricular organ (CVO) with well documented roles in cardiovascular regulation.The present study was undertaken to examine the cardiovascular effects of microinjection of the H2S donor, sodium hydrogen sulfide (NaHS), into the AP of urethane anesthetized male Sprague Dawley rats and the cellular consequences of bath application of NaHS on the excitability of dissociated AP neurons. Microinjection (0.5 μl) of NaHS (10 μM) caused rapid, short duration (<90 sec) decreases in BP (mean area under the curve (AUC) =−389.2 ± 82.6 mmHg*sec, n=6) and HR (mean AUC = −6.6 ± 1.4 beats, n=6) while whole cell perforated patch electrophysiology revealed that bath application of NaHS (1mM) elicited solely hyperpolarizing responses (mean Δ in membrane potential = −3.6 ± 0.8 mV, n=8) in the majority (n=8/13) of AP neurons tested. These observations identify the AP as a CNS location at which H2S may act to influence cardiovascular regulation.Support or Funding InformationSupported by Canadian Institutes of Health Research