Effects of in vitro lead exposure on voltage-sensitive calcium channels differ among cell types in central neurons of Lymnaea stagnalis.
The effects of acute in vitro lead exposure on slowly inactivating voltage-sensitive calcium channels in central neurons of the freshwater pond snail Lymnaea stagnalis were studied under voltage clamp. Three physiologically distinct cell types were used: two subsets of the B cell cluster (Bpos and Bneg) and the pedal giant neuron (RPeD1). In Bpos neurons, 5 nM free Pb2+ irreversibly inhibited current flow through calcium channels by 38 +/- 10%. In Bneg neurons, 5 nM free Pb2+ slightly inhibited inward currents (12 +/- 6%) and may have shifted their voltage dependence to more depolarized voltages. The inhibition and voltage shift were irreversible. In RPeD1 neurons, Pb2+ caused a small, statistically insignificant inhibition of inward current (5 nM free Pb2+; 18 +/- 19%; 30 nM free Pb2+: 31 +/- 23%). The effects of Pb2+ were fully reversible. These data indicate that (1) voltage-sensitive calcium channels in Lymnaea neurons are inhibited by nanomolar concentrations of free Pb2+; (2) there are multiple types of calcium channels in Lymnaea neurons; and (3) the effects of in vitro lead exposure differ qualitatively among channel types.
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Biology Department, University of Colorado, Denver 80204.
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D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D003035:Cobalt / Q000633:toxicity; D004566:Electrodes; D005724:Ganglia / Q000187:drug effects; D007854:Lead / Q000633:toxicity*; D008195:Lymnaea; D009474:Neurons / Q000187:drug effects / Q000648:ultrastructure*; D009498:Neurotoxins
D015220:Calcium Channels; D009498:Neurotoxins; D007854:Lead; D003035:Cobalt