Chemical modulation of in situ intrinsic cardiac neurones influences myocardial blood flow in the anaesthetised dog.
OBJECTIVE
The aim was to determine whether modulation of intrinsic cardiac neurones influences the distribution of myocardial blood flow in canine anaesthetised open chest experimental preparations.


METHODS
Intrinsic cardiac neurones were modified by locally applied nicotine (100 micrograms) or bradykinin (50 micrograms) while changes were recorded in cardiac haemodynamics and myocardial blood flow (radiolabelled microspheres). Right and left ventricular intramyocardial tissue pressures were measured with high fidelity microtip transducers.


RESULTS
Control injections of saline (vehicle; 0.1 ml) into active loci did not produce cardiovascular responses. Nicotine modulation of intrinsic cardiac neurones did not change coronary artery conductance, but total myocardial blood flow [116(SEM 17) v 532(97) ml.min-1.100 g-1; p = 0.001 v baseline] and oxygen consumption [7.92(1.10) v 20.14(1.86) ml.min-1.100 g-1; p = 0.001] increased in direct relation to heart rate-blood pressure product changes. Locally administered bradykinin increased coronary artery conductance [2.62(0.39) v 4.71(1.07) ml.min-1.100 g-1.mm Hg-1], total myocardial blood flow, to 263(72) ml.min-1.100 g-1, and oxygen consumption, to 14.9(4.4) ml.min-1.100 g-1; however, heart rate-blood pressure product did not change.


CONCLUSIONS
These results support earlier findings that intrinsic neurones are involved in cardiac regulation. Furthermore, modification of intrinsic cardiac neurones by nicotine or bradykinin significantly alters the distribution of myocardial blood flow, possibly because of increased myocardial metabolism.
Kingma
J G
JG
Department of Medicine, Faculty of Medicine, Laval University, Ste-Foy, Quebec, Canada.
Armour
J A
JA
Rouleau
J R
JR
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D004285:Dogs; D005260:Female; D006321:Heart / Q000294:innervation*; D008297:Male; D009474:Neurons / Q000187:drug effects*; D009538:Nicotine / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects
D009538:Nicotine; D001920:Bradykinin