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Mammalian differences in vagal‐cholinoceptor control of coronary conductance
Author(s) -
Hamut Mutalip,
Quail Anthony,
Seah Peng,
McLeod Damian,
Cottee David,
White Saxon
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1025.10
Subject(s) - vasoconstriction , coronary arteries , medicine , vasodilation , anesthesia , vagus nerve , stimulation , efferent , cardiology , artery , anatomy , afferent
Although there is no consistency of vagal‐cholinoceptor coronary control mechanisms between species, the anatomical pattern of coronary blood supply in sheep is similar to the dog. The vasodilatation to both acetylcholine (ACh) infusion and electrical stimulation of vagus nerve in the dog, therefore, may also be expected in the sheep. Pulsed Doppler flow probes were implanted on the right (R), circumflex (Cx) and anterior descending (AD) coronary arteries of the sheep. Pressure catheters were placed via the superficial cervical vein and artery in the right atrium and in the aorta respectively. In awake sheep, ACh caused vasodilatation in all three coronary beds. There was a 3‐fold conductance increase in R (p<0.001) compared to 2.5 fold in left‐sided beds (p<0.001). Effective dose 50% (ED50) for Cx was less than that in AD (p<0.05) and in R (p<0.05). In the same sheep under isoflurane anaesthesia and pacing at 150 min −1 direct efferent vagus nerve stimulation caused frequency‐dependent simultaneous vasoconstriction in all three coronary beds. The vasoconstriction was greatest in Cx (p<0.001), intermediate in AD (p<0.001), and least in R (p<0.001). These findings suggest that there are qualitative and quantitative differences between mammalian species. In awake sheep, constrictor cholinoceptors in the media of coronary arteries may play a dominant role. Funding: Hunter Medical Research Institute.