Decreased phosphorylation of synaptic glycoproteins following hippocampal kindling

Rats with chronic electrode implants to region CA3 of the hippocampus were rapidly kindled by stimulation with a 10 s, 10 Hz train of biphasic square waves presented every 5 min, until generalized seizures developed (60-70 stimulations). The hippocampi were isolated from the brains of control animals (implanted but not stimulated), and experimental animals which had developed generalized seizures. Synaptic membranes (SM) were prepared. SM were incubated with [gamma-32P]ATP and the incorporation of 32P into proteins and glycoproteins isolated by affinity chromatography on concanavalin-A-agarose was investigated. There was no difference in the phosphorylation pattern of total SM proteins between groups. In contrast, the phosphorylation of a glycoprotein with an apparent molecular weight of 180,000 was decreased 20-40% in kindled animals. This result was replicated in three independent experiments. The results suggest that the phosphorylation of glycoprotein 180 may be related to neuroplastic events.