Abstract
Stimulation of D1 type of dopamine (DA) receptor induces a slow Na+ current response in the identified neurons of Aplysia ganglia under voltage clamp. We previously reported that the Na+ current response to DA is facilitated by the activation of small GTP-binding protein RhoB or C but not RhoA, and subsequent phospholipase D (PLD). In the present study, we investigated the regulatory mechanism of the DA-induced Na+ current response by Rho and PLD. The Na+ current response to DA was significantly augmented by extracellular application of monodancylcadaverine, an inhibitor of clathrin-mediated endocytosis. In contrast, extracellular application of monensin, an inhibitor for recycling of endocytosed protein to the cytoplasmic membrane, significantly depressed the DA-induced current response. Furthermore, intracellular application of botulinum toxin type B, which cleaves the SNARE protein SNAP-25, also inhibited the Na+ current response to DA. These results suggest that Rho and subsequent PLD may regulate the DA-induced Na+ current response through recycling of the D1 receptor. [J Physiol Sci. 2008;58 Suppl:S56]
