Is the catecholamine secretion chaotic?*

Exocytosis is the release of cellular substances contained in cell vesicles by fusion of the vesicular membrane with the plasma membrane. Adrenaline is a catecholamine released via exocytosis in chromaffin cells. Each exocytosis event exhibits a current spike of adrenaline secretion, which can be detected experimentally through oxidation of adrenaline molecules. Although the form of spikes identifies specific phases of exocytosis, the long-term behavior has not being fully characterized. In this contribution, adrenaline secretion is measured from a set of nine single chromaffin cells via amperometry. Phase space is reconstructed by delay coordinates, power spectrum density is computed using Fast Fourier Transform (FFT) and Maximum Lyapunov Exponent (MLE) is estimated by means of classical algorithms. Thus, this contribution provides preliminary evidence about the possible chaotic behavior in time series from catecholamine secretion.