Kinetic properties of cholinergic desensitization in Aplysia neurons.
The kinetic properties of desensitization onset of excitatory cholinergic responses were studied in isolated, voltage-clamped Aplysia neurons. Desensitization of the acetylcholine (ACh)-induced current in response to microperfused acetylcholine occurred in two phases, and was best modelled as the sum of two exponential components plus a constant. Both exponential components were accelerated by increasing ACh dose. At the higher ACh doses the current decline was dominated by the fast exponential component, and the ratio of the plateau-peak current was reduced. Over the range of membrane potentials -50 to -110 mV, no change in the kinetics of desensitization onset was observed. The mean time constants of both exponential components were doubled by cooling from 20 degrees C to 5 degrees C. These results demonstrate that, as at the vertebrate neuromuscular junction, the onset of desensitization of this ACh response involves at least two processes which are dose- and temperature-sensitive. The lack of voltage dependence contrasts with results from vertebrate preparations, and indicates a fundamental difference between the properties of the excitatory ACh response in Aplysia neurons and the vertebrate neuromuscular junction.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001048:Aplysia; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D013696:Temperature
D000109:Acetylcholine; D011188:Potassium