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Keywords:

  • calcium channel blocker;
  • static magnetic field;
  • geomagnetic field;
  • baroreceptor;
  • baroreflex sensitivity;
  • sensory transduction

Abstract

Previously we found an opposite effect of artificial static magnetic field (SMF) and natural geomagnetic field (GMF) on arterial baroreceptors. A 0.35 T SMF increased baroreflex sensitivity (BRS), whereas GMF disturbance decreased BRS. Here, we investigated interrelated impacts on arterial baroreceptors of 0.35 T SMF, generated by Nd2-Fe14-B alloy magnets, GMF, and verapamil, a Ca2+ channel blocking agent. We measured BRS in rabbits before and after local SMF exposure of sinocarotid baroreceptors or after simultaneous SMF and verapamil application, in conjunction with geomagnetic disturbance during actual experimental run (determined by K-index) and geomagnetic disturbance over the preceding 24 h of each experiment (Ak-index). BRS was estimated from peak responses of mean arterial pressure (MAP) and heart rate, expressed as percentages of the resting values preceding each pair of pressure (phenylephrine) and depressor drug (nitroprusside) injections. Prior to verapamil and/or SMF application we found a significant positive correlation of K-index with MAP (t = 2.39, P = .021, n = 44), but negative with BRS (t = −4.60, P = .0003, n = 44), and found a negative correlation of Ak-index with BRS (t = −2.7, P = 0.01, n = 44). SMF induced an increase in BRS (0.79 ± 0.1 vs. 1.15 ± 0.1 bpm%/mmHg%, initial value vs. SMF exposure, P < .0002, n = 26). Verapamil infusion blocked the SMF and GMF effect on BRS, indicating Ca2+ channels as a possible site of both fields' impact. SMF and GMF probably affect baroreceptor sensory transduction, modulating baroreceptor membranes' Ca2+ channel permeability. Bioelectromagnetics 23:531–541, 2002. © 2002 Wiley-Liss, Inc.