[Ultrastructure of a mechanoreceptor neuron with acceleration of its adptation to an adequate stimulus]

Ultrastructural changes were followed in the isolated mechanoreceptor neurons of the crayfish during post-excitational short-term trace processes (i.e. acceleration of the adaptional state), after repeated adaquate excitations. Fibrillar rearrangements of the mitochondrial cristae in the axonal mitochondria took place at the moderate excitation, no visible changes being seen in the somatic mitochondria and other organelles. However, the swelling of periaxonal areas and the rupture between strands of microtubules and electrogenic membrane occurred at the end of the fatique stimulation. In addition, the swelling of somatic mitochondria in the perinuclear zone and of the reticulum was noticed. Besides, the survival time of the excited isolated neurons strongly depended on the functional state of the surrounding glial cells. It is suggested that energetic processes are strongly involved in the postexcitational short-term traces.