Endocytotic activity of the presynaptic membrane and the morphometric differences of cortical synapses during the excitability changes in the initial phases of kindling.

Cortical sensorimotor areas of the laboratory rats was repeatedly stimulated at 10 min intervals. It led to progressive lengthening of the self-sustained after discharges (SSAD). Ten minutes after termination of the third SSAD the synapses of type I were examined. The ten minutes interval corresponds in electrophysiological experiments with a marked increase of excitability of the investigated cortical area. At the some time, it coincides with the intensification of endocytotic activity on the presynaptic membrane, and with an increase of complex and dense-core vesicles. The exocytotic activity was not changed. The area of the presynaptic elements increased together with their perimeter and maximal diameter. Mitochondria within the presynaptic bags had larger section area. Also the postsynaptic elements became larger, their section area, perimeter and maximal diameter increased. We consider the theory of presynaptic membrane recycling, ion permeability changes, activity of proteosynthesis and the role of contractile proteins during the repeated hyperfunction.