Crambescins and crambescidins are two families of
guanidine alkaloids from the marine sponge Crambe crambe. Although very little information about their
biological effect has been reported, it is known that
crambescidin 816 (Cramb816) blocks
calcium channels in a
neuroblastoma X
glioma cell line. Taking this into account, and the fact that
ion channels are frequent targets for natural toxins, we examined the effect of Cramb816 and three compounds from the crambescin family,
norcrambescin A2 (
NcrambA2),
crambescin A2 (
CrambA2), and
crambescin C1 (CrambC1), in the main voltage-dependent
ion channels in neurons:
sodium,
potassium, and
calcium channels. Electrophysiological recordings of voltage gated
sodium,
potassium, and
calcium currents, in the presence of these
guanidine alkaloids, were performed in cortical neurons from embryonic mice. Different effects were discovered: crambescins inhibited K(+) currents with the following potency:
NcrambA2 > CrambC1 >
CrambA2, while Cramb816 lacked an effect. Only CrambC1 and Cramb816 partially blocked Na(+) total current. However, Cramb816 partially blocked Ca(2+) , while
NcrambA2 did not. Since the blocking effect of Cramb816 on
calcium currents has not been previously reported in detail, we further pharmacologically isolated the two main fractions of HVA Ca(2+) channels in neurons and investigated the Cramb816 effect on them. Here, we revealed that Cav1 or
L-type calcium channels are the main target for Cramb816. These two families of
guanidine alkaloids clearly showed a structure-activity relationship with the crambescins acting on
voltage-gated potassium channels, while Cramb816 blocks the voltage-gated
calcium channel Cav1 with higher potency than
nifedipine. The novel evidence that Cramb816 partially blocked CaV and NaV channels in neurons suggests that this compound might be involved in decreasing the
neurotransmitter release and synaptic transmission in the central nervous system. The findings presented here provide the first detailed approach on the different effects of crambescin and crambescidin compounds in voltage-gated
sodium,
potassium, and
calcium channels in neurons and thus provide a basis for future studies.