FLUORESCENT INVESTIGATION OF THE LIVING MOTOR NERVE ENDING OF THE FROG BY ENDOCYTOTIC
MARKER FM 1-43
A. L. Zefirov,1 * P. N. Grigoryev,1 A. M. Petrov,2
M. G. Minlebaev,1 G. F. Sitdikova 2
1 Department of Normal Physiology, Medical State University, Kazan and
2 Department of Physiology of Animals and Plants, State University, Kazan;
* e-mail: zefirov@kmu-mf.kcn.ru
In our experiments on motor nerve endings of the frog cutaneous pectoris muscle, using fluorescent marker FM 1-43,
the intensity and topography of endocytosis were investigated after the initiation of massive exocytosis of synaptic vesicles by increasing
the extracellular potassium concentration. Using FM 1-43, fluorescent spots were shown to appear, looking as accumulations of
synaptic vesicles in the active zone region. The forms and sizes of luminous spots and the distances between them were analysed.
Considerable variations in brightness and total areas of fluorescent spots per a length unit in different regions of the nerve ending
were revealed in addition to a proximal-distal gradient of these parameters along the nerve terminal. Peculiarities of topography and
intensities of luminescence in the most terminal regions of the nerve ending are described. The obtained data are discussed in terms
of the exo- and endocytosis cycle of synaptic visicles in the active zone region, and from the point of view of the plasticity of the motor
nerve ending and active zones. The factors involved in the transmitter release nonuniformity are analysed.
Key words: neuromuscular junction, nerve ending, active zone, endocytosis, exocytosis, optical me-thods, fluorescence,
FM 1-43
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