[A statistical assessment of the membrane area and of the number of active zones in presynaptic terminals].

Geometrical features of electron microgram profiles of presynaptic terminals (PTs) in the dorsal horn of the cat spinal cord were studied. The statistical approach which has permitted estimating the surface area of the closed membrane on the basis of parameters of its plane random sections is described. Mean surface area of the plasma membrane of observed PTs is estimated. The probability estimate of the mean number of active zones per each presynaptic bouton is considered. The obtained quantitative data are discussed for the possibility to describe physical processes occurring in presynapses.