Modulation of potassium current kinetics in bag cell neurons of Aplysia by an activator of adenylate cyclase.
The bag cell neurons of Aplysia are neurosecretory cells which control egg-laying behavior. In their resting state, the cells have a high resting potential and show no spontaneous activity. In response to brief stimulation of a neural input, the cells depolarize and fire repetitively for up to 60 min. This afterdischarge is thought to be controlled by elevations of intracellular adenosine 3':5'-monophosphate (cAMP). A voltage clamp study of bag cells in primary culture was undertaken in order to characterize the effects of cAMP on the cells' electrical properties. The transient outward potassium current (A-current) was studied before and after the application of forskolin (an activator of adenylate cyclase) and RO20-1724 (a phosphodiesterase inhibitor). These drugs reduced the amplitude of the A-current, primarily by speeding the inactivation process. The time constants for inactivation were speeded at all potentials, but the largest effects were seen at the more positive potentials (-40 to -15 mV), where the time constants were reduced 5-fold. Neither the activation process nor the steady-state parameters of inactivation were altered by the drugs. It is suggested that these changes in the A-current could explain the ability of the bag cells to fire repetitively during the afterdischarge.
D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone / Q000494:pharmacology; D000200:Action Potentials; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D002478:Cells, Cultured; D005576:Colforsin; D000242:Cyclic AMP / Q000502:physiology; D004224:Diterpenes / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D009474:Neurons / Q000502:physiology*; D009490:Neurosecretory Systems / Q000502:physiology; D011188:Potassium / Q000378:metabolism*
D004224:Diterpenes; D007473:Ion Channels; D005576:Colforsin; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D011188:Potassium