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 1. Ca2+ mobilization by N-acetyl-serotonin (NAS) in intact P. chabaudi parasites. Intact parasites at the trophozoite stage were loaded with Fluo-3 AM (see Material and Methods). The reaction medium contained 2 mM Ca2+ in panel A and 12 mM EGTA in panel B. Where indicated, 0.1 mM NAS, 0.1 mM melatonin (MLT) or 100 nM thapsigargin (THG) was added to parasite suspensions (A-G). Addition of 0.1 mM NAS to cells pretreated with 250 mM luzindole (F, 50 min) or with 20 mM U73122 (G, 1 min) did not elicit a Ca2+ response. However, the addition of thapsigargin released Ca2+. Results are typical of at least three independent cell preparations. ER = endoplasmic reticulum.