Blockade of Vasoconstrictor Responses by Prostacyclin (PGI2), PGE2, and PGE1 in the Rabbit Hindquarters Vascular Bed

The effects of infusions of prostacyclin (PGI2), PGE2 and PGE1 on responses to pressor hormones and sympathetic nerve stimulation were investigated in the hindquarters vascular bed of the rabbit. During infusions of PGI2, PGE2 and PGE1 vasoconstrictor responses to norepinephrine, nerve stimulation and angiotensin II were decreased. Responses to the pressor hormones and nerve stimulation were decreased to a similar extent by PGI2 and responses returned to control value 30 min after the infusion. During infusions of PGE2 and PGE1 responses to nerve stimulation were decreased to a somewhat greater extent than responses to pressor hormones and the inhibitory action of these substances had a longer duration of action than PGI2. Indomethacin in doses that blocked depressor responses to arachidonic acid was without consistent effect on responses to nerve stimulation and pressor hormones. The present data show that E series prostaglandins and PGI2 possess the ability to modulate responses to nerve stimulation and pressor hormones; however, experiments with indomethacin suggest that endogenous prostaglandins do not modulate vasoconstrictor responses in the rabbit hindquarters.