Exocytosis is known to provide such a vital processes as the release of neurotransmitters in synaptic transmission or release of hormones during secretion. The main mechanism of exocytotic process occurs through the specialized protein complex called the SNARE-complex. Due to its activity the fusion of vesicular and plasma membrane occurrs and fusion pore is formed through which a content of vesicles is released outside. It is believed that just synaptotagmins which are Ca2+-dependent proteins, responsible for initiation of the process of Ca2+-dependent exocytosis. Synaptotagmins are located at the membrane of the vesicles and can bind two or three Ca2+ ions. In our research, we studied the role of one of the most common isoform of synaptotagmines - synaptotagmin-1. For this we used an injection of antibodies arised to synaptotagmin-1 (anti-STg-1) into isolated rat adrenal chromaffin cells to depress the function of this protein. Catecholamine secretion was measured by amperometric method. Our results showed that an exclusion of synaptotagmin-1 function in tested cells resulted in significant supression of secretion. These data allow us to conclude that synaptotahmin-1 is a key protein which is needed for Ca2+-dependent exocytosis in chromaffin cells.