“…Pharmacological actions of prostaglandin E1 (PGE1) on the central nervous system (CNS) have been demonstrated in cats by injection into the cerebral ventricles (Horton, 1964;Horton & Main, 1965), by micro-iontophoretic application (Avanzino, Bradley & Wolstencroft, 1966), by intravenous injection (Horton & Main, 1967) and by close-arterial injection to the spinal cord (Duda, Horton & McPherson, 1968). Although only relatively small doses are required to produce these effects in cats and also on intravenous injection in young chicks (Horton, 1964;Horton & Main, 1965, 1967, it has been shown in other species (rats, mice and sheep) that little or no tritium-labelled prostaglandin E1 reaches the CNS following intravenous injection (Hansson & Samuelsson, 1965;Samuelsson, 1964Samuelsson, , 1965.…”