title: Alteration of calcium conductances and outward current by cyclic adenosine monophosphate (cAMP) in neurons of Limax maximus.
abstract: Membrane responses to cyclic adenosine monophosphate (cAMP) injections have been studied by means of voltage clamp, Ca-indicator dye, and ion substitution techniques in identified neurons from the abdominal ganglion of Limax maximus. The ventral abdominal giant cell (AGC) displayed a response consisting of a decrease in outward current usually accompanied by a smaller enhancement of voltage-gated Ca2+ influx. Both responses were eliminated by external Cd2+ or Mn2+ and required membrane voltages more positive than -40 mV for expression. The enhanced influx persisted in Ba2+-substituted saline, while the decrease in outward current was blocked. A group of dorsal neurons (RD1-3, LD1) showed a mixed Na-Ca influx induced by cAMP that could be activated over a wide range of membrane potentials (less than -100 to greater than -20 mV). This flux caused a measurable increase in internal Ca2+. The influx was insensitive to Cd2+ and Mn2+ but was reduced by prolonged exposure to Co2+. The relative magnitude of the Na-Ca flux ratio showed considerable variation between specimens. In immature animals the Ca component was absent. The results demonstrated that elevation of intracellular cAMP can cause cell-specific changes of membrane conductance within closely associated neurons.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology*; D005724:Ganglia / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials; D008974:Mollusca; D009431:Neural Conduction / Q000187:drug effects; D012964:Sodium / Q000378:metabolism
chemical_list: D007473:Ion Channels; D012964:Sodium; D000242:Cyclic AMP; D002118:Calcium