Effects of huwentoxin-I on catecholamines in cultured PC12 cells.

The measurement of catecholamines in biological samples remains a current analytical challenge in the study on neurotransmitter release, although much effort has been devoted toward the relevant methodology. Here we first established a fluoresence-based method for the quantitative determination of catecholamines and then applied it to the investigation of effects of huwentoxin-I (HWTX-I), a peptide neurotoxin, on catecholamines in cultured PC12 cells. The results showed that treatment with HWTX-I at different concentrations (10, 50, 100 and 1000 nM) for 20 min significantly increased dopamine (DA) content in the culture medium (p < 0.01), with ∼1.6-fold increase compared with that of the control at the highest concentration tested. Within 20 min, DA content in the medium increased with increasing the treatment time. In contrast, HWTX-I decreased norepinephrine (NE) content in the medium. However, after the PC12 cells were treated with HWTX-I, the intracellular contents of both DA and NE were kept at a relatively constant level. These data suggest that HWTX-I differentially affects the DA and NE of the neuroendocrine cells, with enhancing the actions of DA and weakening those of NE.