Abstract
Application of dopamine (DA) induces a slow Na+ current response in the identified neurons of Aplysia ganglia under voltage clamp. This type of response is produced by the activation of trimeric G-protein sensitive to cholera toxin. We previously reported that the Na+ current response to DA is facilitated by the activation of monomeric G-protein Aplysia Rho which is closely homologous to RhoA, RhoB or RhoC in mammalian neuron. In the present study, we investigated possible effector molecules located at the downstream of the Rho in facilitation of the DA-induced response. The Na+ current response to DA was gradually depressed after intracellular injection of α-synuclein, an inhibitory protein for phospholipase D (PLD). Furthermore, extracellular application of butan-1-ol, which is known to inhibit PLD activity, significantly depressed the DA-induced current response, whereas butan-2-ol, an inactive isomer of butan-1-ol, had no significant effect appreciably. These results suggest that the facilitating effect of Rho on the DA-induced Na+ current response may be mediated by the activation of PLD. [J Physiol Sci. 2007;57 Suppl:S145]
