ENHANCEMENT OF MESSENGER-RNA EXPRESSION OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR BY L-THREO-3,4-DIHYDROXYPHENYLSERINE IN ASSOCIATION WITH OCULAR DOMINANCE PLASTICITY

Tissue-type plasminogen activator (tPA) plays important roles in the r egulation of synaptic plasticity in the hippocampus and cerebellum. We found that the expression of tPA mRNA in the visual cortex was increa sed significantly by the peripheral administration of L-threo-3,4-dihy droxyphenylserine (L-threo-DOPS; 100 mg/kg, i.p.), which we had previo usly shown to have a promotive effect on ocular dominance (OD) plastic ity. When plasminogen activator inhibitor-1 (PAI-I; 100 mu M in an osm otic minipump) was infused into the kitten visual cortex, OD plasticit y was suppressed; i.e. a significantly large number of binocular cells was recorded in the PAI-1-infused cortex following monocular deprivat ion. These results, therefore, suggest that the PA system is involved in the promotive effect of L-threo-DOPS in OD plasticity.