PMID:9120560

Citation	Wicher, D and Penzlin, H (1997) Ca2+ currents in central insect neurons: electrophysiological and pharmacological properties. J. Neurophysiol. 77:186-99
Abstract	Ca2+ currents in dorsal unpaired median (DUM) neurons isolated from the fifth abdominal ganglion of the cockroach Periplaneta americana were investigated with the whole cell patch-clamp technique. On the basis of kinetic and pharmacological properties, two different Ca2+ currents were separated in these cells: mid/low-voltage-activated (M-LVA) currents and high-voltage-activated (HVA) currents. M-LVA currents had an activation threshold of -50 mV and reached maximal peak values at -10 mV. They were sensitive to depolarized holding potentials and decayed very rapidly. The decay was largely Ca2+ dependent. M-LVA currents were effectively blocked by Cd2+ median inhibiting concentration (IC50 = 9 microM), but they also had a remarkable sensitivity to Ni2+ (IC50 = 19 microM). M-LVA currents were insensitive to vertebrate LVA channel blockers like flunarizine and amiloride. The currents were, however, potently blocked by omega-conotoxin MVIIC (1 microM) and omega-agatoxin IVA (50 nM). The blocking effects of omega-toxins developed fast (time constant tau = 15 s) and were fully reversible after wash. HVA currents activated positive to -30 mV and showed maximal peak currents at + 10 mV. They were resistant to depolarized holding potentials up to -50 mV and decayed in a less pronounced manner than M-LVA currents. HVA currents were potently blocked by Cd2+ (IC50 = 5 microM) but less affected by Ni2+ (IC50 = 40 microM). These currents were reduced by phenylalkylamines like verapamil (10 microM) and benzothiazepines like diltiazem (10 microM), but they were insensitive to dihydropyridines like nifedipine (10 microM) and BAY K 8644 (10 microM). Furthermore, HVA currents were sensitive to omega-conotoxin GVIA (1 microM). The toxin-induced reduction of currents appeared slowly (tau approximately 120 s) and the recovery after wash was incomplete in most cases. The dihydropyridine insensitivity of the phenylalkylamine-sensitive HVA currents is a property the cockroach DUM cells share with other invertebrate neurons. Compared with Ca2+ currents in vertebrates, the DUM neuron current differ considerably from the presently known types. Although there are some similarities concerning kinetics, the pharmacological profile of the cockroach Ca2+ currents especially is very different from profiles already described for vertebrate currents.
Links	PubMed
Keywords	Animals; Calcium Channel Agonists/pharmacology; Calcium Channel Blockers/pharmacology; Calcium Channels/drug effects; Calcium Channels/physiology; Electrophysiology; Ganglia, Invertebrate/cytology; Ganglia, Invertebrate/drug effects; Ion Channel Gating/drug effects; Ion Channel Gating/physiology; Kinetics; Membrane Potentials/drug effects; Membrane Potentials/physiology; Neurons/drug effects; Neurons/physiology; Neurotoxins/toxicity; Patch-Clamp Techniques; Periplaneta/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AGEAP:TOG4A		GO:0019855: calcium channel inhibitor activity	ECO:0000314:		F		Fig. 6	complete CACAO 4356
CONMA:CO7C		GO:0019855: calcium channel inhibitor activity	ECO:0000314:		F		Fig. 6	complete CACAO 4364

References

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