Key result
5-hydroxytryptamine produced contraction in large and medium canine coronary arteries, but small arteries (<1 mm OD) were unresponsive under resting conditions.
Unlike larger epicardial arteries, small canine coronary arteries (<1 mm outside diameter) do not contract to 5-hydroxytryptamine under resting conditions, and this lack of response is not due to endothelial inhibition.
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May caution against extrapolating serotonergic effects across coronary sizes in humans; leaves open endothelial modulation in vivo.
Gutterman et al. (2008) studied this question. 5-hydroxytryptamine (5HT) was evaluated on Contraction response to 5HT. 5-hydroxytryptamine produced contraction in large and medium canine coronary arteries, but small arteries (<1 mm OD) were unresponsive under resting conditions.
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