Identification and characterization of a Ca(2+)-sensitive nonspecific cation channel underlying prolonged repetitive firing in Aplysia neurons.
The afterdischarge of Aplysia bag cell neurons has served as a model system for the study of phosphorylation-mediated changes in neuronal excitability. The nature of the depolarization generating the afterdischarge, however, has remained unclear. We now have found that venom from Conus textile triggers a similar prolonged discharge, and we have identified a slow inward current and corresponding channel, the activation of which seems to contribute to the onset of the discharge. The slow inward current is voltage-dependent and Ca(2+)-sensitive, reverses at potentials slightly positive to O mV, exhibits a selectivity of K approximately equal to Na >> Tris > N-methyl-D-glucamine (NMDG), and is blocked by high concentrations of tetrodotoxin. Comparison of these features with those observed in channel recordings provides evidence that a Ca(2+)-sensitive, nonspecific cation channel is responsible for a slow inward current that regulates spontaneous repetitive firing and suggests that modulation of the cation channel underlies prolonged changes in neuronal response properties.
Wilson
G F
GF
Department of Pharmacology, Yale University, New Haven, Connecticut 06510, USA.
Richardson
F C
FC
Fisher
T E
TE
Olivera
B M
BM
Kaczmarek
L K
LK
D000818:Animals; D001048:Aplysia; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002412:Cations / Q000378:metabolism; D002478:Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D020916:Conotoxins; D004594:Electrophysiology; D017952:Ganglia, Invertebrate / Q000187:drug effects; D008978:Mollusk Venoms / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D012680:Sensitivity and Specificity; D013779:Tetrodotoxin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002412:Cations; D020916:Conotoxins; C059360:Conus textile toxin; D008978:Mollusk Venoms; D010455:Peptides; D013779:Tetrodotoxin