Chronotropic and dromotropic actions of acetylcholine on the developing fetal heart.
We studied the effect of acetylcholine (ACh), 1 x 10(-8) to 5 x 10(-7) M, on electrophysiologic characteristics of the isolated (Langendorf), perfused fetal canine heart. ACh induced concentration-dependent decreases in sinoatrial (SA) rate and recovery from overdrive pacing and in atrioventricular (A-V) conduction. These effects of ACh were greater in mid-gestation than late-gestation hearts. The effects of ACh were potentiated by inhibition of acetylcholinesterase by neostigmine, 1 x 10(-7) M, in the late- but not the mid-gestation fetal heart. Decreasing the pH of the perfusion solution from 7.3 to 6.8 potentiated the response to ACh of SA rate and A-V conduction more in mid- than in late-gestation hearts. The response to ACh of the late-gestation fetal canine heart is more sensitive to cholinesterase inhibition whereas the response of the mid-gestation heart is more sensitive to the action of ACh in the presence of acidosis.
Danilo
P
P
Department of Pharmacology, Columbia University, College of Physicians and Surgeons, New York, N.Y. 10032.
Binah
O
O
Hordof
A
A
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001283:Atrioventricular Node / Q000187:drug effects; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D006321:Heart / Q000187:drug effects* / Q000196:embryology*; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009388:Neostigmine / Q000494:pharmacology; D011247:Pregnancy; D012849:Sinoatrial Node / Q000187:drug effects
D002800:Cholinesterase Inhibitors; D009388:Neostigmine; D000109:Acetylcholine