Changes in synaptic membrane phosphorylation after tetanic stimulation in the dentate area of the rat hippocampal slice.

Slices of rat brain hippocampus were stimulated electrically in the perforant pathway. After electrical stimulation, known to produce long-lasting post-tetanic potentiation, endogenous phosphorylation of membrane proteins was measured in a crude mitochondrial fraction, prepared from stimulated and unstimulated slices. Tetanic stimulation specifically enhanced the incorporation of [32P]phosphate into a protein band with apparent molecular weight of 50K. When the same number of pulses were given, but at a much slower rate (1 pulse per 4 sec instead of 15 pulses per sec) no posttetanic stimulation and concomitantly, no enhanced incorporation of [32P]phosphate were observed into the 50K band. When the stimulation of the slices was performed in Ca2+-free medium, again no potentiation and no enhanced incorporation into the 50K protein band were observed. It is suggested that electrical stimulation enhances the activity of the protein kinase that phosphorylates the 50K protein.