Acute actions of marine toxin latrunculin A on the electrophysiological properties of cultured dorsal root ganglion neurones

The effects of latrunculin A, isolated from the nudibranch Chromodoris sp., on the excitability of neonatal rat cultured dorsal root ganglion neurones were investigated using patch-clamp recording and Ca2+ imaging techniques. Under current-clamp conditions, acute application of latrunculin A (100 μM) reversibly induced multiple action potential firing and significantly increased action potential duration. No significant effects on action potential peak amplitude, threshold of action potential firing, resting membrane potential and input resistance were observed. Under voltage-clamp conditions, significant and dose-dependent suppression of K+ current was seen with 10–100 μM latrunculin A. Additionally, a significant difference between inhibition of the current measured at the peak and the end of a 100 ms voltage step was seen with 100 μM latrunculin A. Fura-2 fluorescence Ca2+ imaging revealed that latrunculin A (100 μM) significantly inhibited Ca2+ transients evoked by KCl-induced depolarisation in all neurones. In 36% of DRG neurones, latrunculin A alone had no effect on intracellular Ca2+. In 64% of neurones, latrunculin A alone evoked a transient rise in intracellular Ca2+. Moreover, latrunculin A (10–100 μM) significantly inhibited the mean high voltage-activated Ca2+ current. The effects of latrunculin A on action potential firing and K+ currents were attenuated by intracellular phalloidin, an indication that these effects are mediated through actin disruption.