Polygodial-induced noradrenaline release in human neuroblastoma SH-SY5Y cells

Polygodial is a natural sesquiterpene which exhibits pronounced pungency and a powerful antifeedant activity. At low concentrations, which do not alter general cell membrane permeability, polygodial increases the intracellular concentration of free calcium ([Ca(2+)](i)). Sensory neurotransmission depends on noradrenaline (NA) release, and vesicular exocytosis, in turn, is dependent on an increase in [Ca(2+)](i). The nociceptive response induced by polygodial could therefore be directly linked to intracellular calcium levels. Consequently, the objective of this work was to investigate the effect of polygodial on NA release. The human neuroblastoma cell line SH-SY5Y was selected as an in vitro model for sensory neurones. Semiconfluent cells were preloaded with tritiated NA ([(3)H]NA). After 3 min exposure of polygodial to the cells, released and unreleased radioactivity were measured. Polygodial induced a significant [(3)H]NA release at concentrations between 0.1 and 0.5 mug/ml with a maximum effect at 0.2 mug/ml (40% increased release of [(3)H]NA as compared with unstimulated control cells). No polygodial-induced transmitter release was seen at 3.5 and 5 mug/ml. For comparison, carbachol (1 rim) increased [(3)H]NA release by 10% and the KCl-induced (100 mm) [(3)H]NA release increased by 8% as compared with unstimulated SH-SY5Y cells. In conclusion polygodial, at the concentrations 0.1-0.5 mug/ml (equal to 0.4-2 mum), induces NA release which is dependent on polygodial-induced increase in [Ca(2+)](i).