Regional differences in serotonergic contractile sensitivity mediated by 5-HT2 receptors in rat aorta.

The present studies examined serotonergic contractile sensitivity mediated by 5-HT2 receptors in thoracic and abdominal regions of rat aorta. Increasing concentrations of 5-HT (10 nM-100 microM) in the presence or absence of the selective 5-HT2 antagonist ketanserin (5 nM) produced differential concentration-response curves in thoracic and abdominal aortic ring preparations. Abdominal aortic preparations were significantly more sensitive to 5-HT than thoracic regions. Regional variations in maximal response produced by 5-HT were not observed. Ketanserin produced distinct rightward shifts in the 5-HT concentration-response curves, revealing a similar profile of sensitivity in thoracic and abdominal aorta. These data suggest that regional patterns in 5-HT-induced contractile responses in rat aorta are mediated by 5-HT2 sites exhibiting differential, site specific sensitivity.