Inhibitory effects of fucoidan on NMDA receptors and l-type Ca channels regulating the Ca responses in rat neurons.

CONTEXT

Fucoidan, a sulphated polysaccharide extracted from brown algae [Fucus vesiculosus Linn. (Fucaceae)], has multiple biological activities.

OBJECTIVE

The effects of fucoidan on Ca responses of rat neurons and its probable mechanisms with focus on glutamate receptors were examined.

MATERIALS AND METHODS

The neurons isolated from the cortex and hippocampi of Wistar rats in postnatal day 1 were employed. The intracellular Ca responses triggered by various stimuli were measured in vitro by Fura-2/AM. Fucoidan at 0.5 mg/mL or 1.5 mg/mL was applied for 3 min to determine its effects on Ca responses. RT-PCR was used to determine the mRNA expression of neuron receptors treated with fucoidan at 0.5 mg/mL for 3 h.

RESULTS

The Ca responses induced by NMDA were 100% suppressed by fucoidan, and those induced by Bay K8644 90% in the cortical neurons. However, fucoidan has no significant effect on the Ca responses of cortical neurons induced by AMPA or quisqualate. Meanwhile, the Ca responses of hippocampal neurons induced by glutamate, ACPD or adrenaline, showed only a slight decrease following fucoidan treatment. RT-PCR assays of cortical and hippocampal neurons showed that fucoidan treatment significantly decreased the mRNA expression of NMDA-NR1 receptor and the primer pair for l-type Ca channels, PR1/PR2.

DISCUSSION AND CONCLUSIONS

Our data indicate that fucoidan suppresses the intracellular Ca responses by selectively inhibiting NMDA receptors in cortical neurons and l-type Ca channels in hippocampal neurons. A wide spectrum of fucoidan binding to cell membrane may be useful for designing a general purpose drug in future.