title: [Effect of NO on automaticity of rabbit sino-atrial node].
abstract: OBJECTIVE
  To investigate the effects of exogenous NO donors sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1) on automaticity of the rabbit sino-atrial node in vitro and the action mechanism.
  
  
  METHODS
  The intracellular microelectrode technique is used to record the action potentials of rabbit sino-atrial node and APA (amplitude of AP), V(max) (maximal rate of depolarization), VDD (velocity of diastolic depolarization), RPF (rate of pacemaker firing) are analyzed.
  
  
  RESULTS
  SNP(10(-5) - 10(-2) mol/L) increased its RPF and VDD dose-dependently. 10(-3) mol/L SNP increased RPF (beats/min) from 163 +/- 10.8 to 195.0 +/- 13.1 increased VDD (mV/s) from 50.3 +/- 9.6 to 70.2 +/- 12.1 (P < 0.01). SIN-1(10(-3) - 10(-2) mol/L) also increased RPF and VDD (P < 0.01).10(-4) mo/L Methylene blue (MB), a blocker of GMP cyclase, prevented the positive chronotropic effect and increasement of VDD induced by 10(-3) mol/L SNP totally (P < 0.01). 2. CsCl (2 mmol/L), a blocker of I(f) prevented the increasement of RPF and VDD in part (P < 0.05). 3. NIF (0.46 micromol/L), a blocker of I(Ca-L, had no significant effects on chronotropic effect and increasement of VDD (P < 0.01).
  
  
  CONCLUSIONS
  Exogenous NO can increase the automaticity of rabbit sino-atrial node in vitro. The chronotropic effect is involved in NO-cGMP pathway and results from increasement of I(f) in the sino-atrial node at least in part; I(ca-L) is unlikely to play a major role in this effect.
authors.affiliation: Department of Physiology, Guangzhou Medical College, Guangzhou 510182, China.
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Si
authors.forename: Sheng-Ai
authors.initials: SA
authors.lastname: Hu
authors.forename: Qing-Shan
authors.initials: QS
authors.lastname: Wang
mesh_terms: D000200:Action Potentials; D000818:Animals; D006339:Heart Rate; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000187:drug effects* / Q000502:physiology
chemical_list: D009599:Nitroprusside; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine