SENSITIVITY OF PLASMINOGEN ACTIVATOR SYSTEM TO CHANGES IN VISUAL STIMULATION

F. FUENTES; V. SÁNCHEZ; A.L. ORTALLI; J. LUJILDE; A. SCICOLONE; M. RAPACIOLI; G. SCICOLONE; V. FLORES

New Orleans, USA

Congreso; Society for Neuroscience. 33rd. Annual Meeting; 2003

Society for Neuroscience

To study the developmental pattern of plasminogen activator (PA) system and possible plastic changes related to alterations in visual stimulation we used optic lobes of White Leghorn chiken embryos and postnatal chicks rearedunder different conditions: 1) a cycle of 12h light – 12h darkness and 2) a cycle of 12h dim light – 12 h darkness. We used a Triton treated fraction derived from a crude membrane fraction to quantify PA activity with a fibrinolytic assay and urokinase (uPA) and PA inhibitor 1 (PAI1) expression with ELISA. PA activity shows peaks at 12 and 18 days of incubation (E12/18) and persists at high levels for the 12 first postnatal days (P) as synaptic plasticity is a main event. There is a peak between P6 and P12. uPA expression increases since E10 and shows a similar postnatal profile to PA activity. PAI1 shows a peak at E14 as PA activity decreases and presents a transitory decrease between P6 and P12. These results suggest that the decrease of PA activity at E14 could depend on an increase of PAI1 and that the increase of PA activity between P6 and P12 could be caused by an increase in uPA and a decrease in PAI1 levels. Subnormal stimulated chicks do not show the increase in PA activity and these agrees with the lack of increase in uPA and decrease of PAI1 expression at the same period. As these animals are returned to normal conditions, they show an increase in uPA and a decrease of PAI1 expression. Results suggest that visual stimulation produces an increase in PA activity that could be mediated by an increase in uPA and a decrease in PAI1 expression. This peak in PA activity coincides with important events of synaptic plasticity and allows us to postulate that it could participate in synaptic remodeling by degrading extracellular matrix. Besides, the system keeps the plasticity to recover the normal level of uPA activity during early postnatal life.