title: Interaction of the autonomic nervous system with intrinsic cardiac rate regulation in the guinea-pig, Cavia porcellus.
abstract: In the denervated mammalian heart a change in right atrial pressure will still alter heart rate (intrinsic rate response, IRR). We have examined the IRR in isolated right atria of the guinea-pig maintained in oxygenated Krebs-Henseleit solution at 37 degrees C, to compare with and extend studies in other species, and to determine whether the guinea-pig is a suitable model for electrophysiological studies of the IRR. Baseline diastolic transmural pressure was set at 2 mmHg. A 6-mmHg increase in right atrial pressure (RAP) caused an increase in atrial rate that reached a steady value of 15 min(-1) after 1-2 min. This response was enhanced by carbamylcholine and attenuated by isoprenaline. The influence of RAP on the rate response to vagal stimulation was examined. With RAP set at 8 mmHg, the reduction in atrial rate following vagal stimulation was 72+/-5% of that at 2 mmHg (n=6, mean+/-S.E., P<0.005). Continuous vagal stimulation produced a sustained bradycardia, and the effect of this bradycardia on the IRR was examined. When atrial rate was reduced 6% by vagal stimulation, the IRR was augmented to 202+/-21% of the control (n=6, P<0.005). This augmentation was larger (P<0.05) than that seen when atrial rate was reduced 8% by carbamylcholine (130+/-8% of control; n=7, P<0.05). Overall, the IRR in the guinea-pig is similar to that in the rabbit, and shows similar interactions with the autonomic nervous system.
authors.affiliation: Department of Physiology and the Centre for Neuroscience, School of Medical Sciences, University of Otago, P.O. Box 913, Dunedin, New Zealand.
authors.forename: S J
authors.initials: SJ
authors.lastname: Wilson
authors.forename: C P
authors.initials: CP
authors.lastname: Bolter
mesh_terms: D000818:Animals; D016275:Atrial Function; D001341:Autonomic Nervous System / Q000378:metabolism*; D001919:Bradycardia; D002217:Carbachol / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D004594:Electrophysiology; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate; D007545:Isoproterenol / Q000494:pharmacology; D011312:Pressure
chemical_list: D002316:Cardiotonic Agents; D002217:Carbachol; D007545:Isoproterenol