Melatonin and N-acetyl-serotonin cross the red blood cell membrane and evoke calcium mobilization in malarial parasites. C.T. Hotta, R.P. Markus and C.R.S. Garcia. Brazilian Journal of Medical and Biological Research, 36 (11): 1583, 2003.

Figure 2. Ca2+ mobilization by melatonin and N-acetyl-serotonin (NAS) in red blood cells (RBC) infected with P. chabaudi parasites. Infected RBC at the trophozoite stage were loaded with Fluo-3 AM. The reaction medium contained 2 mM Ca2+. Where indicated, 0.1 µM melatonin (MLT) or 0.1 µM NAS was added to the cell suspensions. Experiments were performed with a Hitachi F-4500 spectrofluorometer (A,B) or a Zeiss LSM-510 confocal microscope (C-J). C and G, Phase contrast. Fluorescence of infected RBC before the addition of 0.1 µM MLT (D) or 0.1 µM NAS (H). E and I, Co-localization of the previous images. Fluorescence after the addition of 0.1 µM MLT (F) or 0.1 µM NAS (J). K,L, Fluorescence intensity (DF/F0) normalized as a function of time.