Prostaglandin E 1-induced alterations in visually-evoked response and production of epileptiform activity

Abstract

The effects of supracortically applied prostaglandin (PG) E 1 on the visually-evoked response (VER) and the spontaneous electrocorticogram (ECoG) were studied in conscious rabbits before and after systemic pretreatment with inhibitors of PG transport or synthesis. (1) Within a few minutes after injection of bromcresol green or probenecid, suprafusion of 8 μg of PGE, over the visual cortex produced alterations in the VER frequently followed by epileptiform activity. Before, or 24 hr after bromcresol green or probenecid administration, suprafusion of PGE 1 had no observable effect on cortical electrical activity. (2) Similar or even more pronounced PGE 1-induced effects were observed 90 min to 24 hr after, but not less than 90 min after, pretreatment with PG synthesis inhibitors, indomethacin or paracetamol. (3) Essentially similar results were obtained with PGE, while suprafusion of 8 μg of PGF 2, after pretreatment with a PG transport or synthesis inhibitor had no observable effect on the VER or ECoG. (4) It is concluded that accumulation of high levels of exogenous PGE within the cortical layers of PG transport inhibitor-pretreated rabbits, or development of supersensitivity to PGs in PG synthesis inhibitor-pretreated animals, can render the brain vulnerable to E type PGs with resulting alterations in the VER and production of epileptiform activity. It is suggested that the observed effects maybe due to PGE-induced modulation of normal inhibitory pathways.