Changing of an isolated neurone ultrastructure during a prolonged impact of mediator

We investigated the influence of prolonged excitation or combined excitation/inhibition on the ultrastructural changes in an isolated stretch receptor neurone from crayfish abdomen. Excitatory impulse activity was achieved by mechanical stimulation of a neurone for 10 or 120 min and inhibition of the activity was obtained by perfusion with gamma-aminobutyric acid (GABA, 2.5 x 10(-5) M) for the same periods. Changes in the ultrastructural components were observed following both excitatory and inhibitory stimulation for 120 min. Neuronal adaptation to excitatory or inhibitory stimuli after 120 min resulted in the appearance of an increased number of the giant mitochondria. Thus, the number of giant mitochondria may serve as an ultrastructural index of the degree of neuronal adaptation to external stimulation.