title: Voltage Dependence of a Neuromodulator-Activated Ionic Current.
abstract: The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca(2+), but that, in conditions of low Ca(2+), calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca(2+)/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR.
authors.affiliation: Behavioral and Neural Science Graduate Program, Rutgers University-Newark, Newark, New Jersey 07102; Federated Department of Biological Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102.
authors.forename: Michael
authors.identifier: 0000-0002-5969-5631
authors.initials: M
authors.lastname: Gray
authors.affiliation: Federated Department of Biological Sciences, New Jersey Institute of Technology , Newark, New Jersey 07102.
authors.forename: Jorge
authors.identifier: 0000-0002-6183-3175
authors.initials: J
authors.lastname: Golowasch
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000502:physiology*; D001703:Biophysics; D003386:Brachyura; D002116:Calcitonin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000166:cytology*; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D009842:Oligopeptides; D010446:Peptide Fragments; C412708:calcium-like peptide CALP1; C011536:proctolin; C037553:katacalcin; D002116:Calcitonin; D003620:Dantrolene; D002118:Calcium
keywords: activity; calcium sensing receptor; calcium-dependence; central pattern generation; crustacean; stomatogastric