Cardiovascular effects of prostaglandins mediated by the central nervous system of the dog.

1. Prostaglandins A(1), E(1), F(1alpha) and F(2alpha) were infused into the vertebral artery of the chloralose-anaesthetized greyhound and the resulting cardiovascular responses were compared with those obtained on intravenous and intracarotid infusions in the same dose range.2. Infusions of PGF(2alpha) intravertebrally (4-64 (ng/kg)/min) caused an increase of blood pressure, tachycardia and a fall of central venous pressure. Cardiac output was increased and peripheral resistance was essentially unchanged. There was never any response to intravenous or intracarotid PGF(2alpha) infusions in this dose range.3. PGF(1alpha) was found to have similar effects to PGF(2alpha) but it was much less potent.4. PGE(1) infusions (4-360 (ng/kg)/min) into the vertebral artery caused a tachycardia which was greater than that obtained with intracarotid or intravenous infusions, but there was no significant effect on blood pressure.5. Infusions of PGA(1) caused a small fall of blood pressure accompanied by an increase of heart rate and the dose response relationships were similar for all three routes of administration.6. It is concluded that some prostaglandins can activate cardioregulatory centres within the territory of distribution of the vertebral artery. Prostaglandin F(2alpha) is the most potent of these.