Native nicotinic acetylcholine receptors in human Imr32 neuroblastoma cells: functional, immunological and pharmacological properties.
IMR32 cells express two classes of surface nicotinic receptors: those labelled with high affinity by [125I]neuronal toxin, and those labelled by [125I]alpha-bungarotoxin. Whole-cell patch-clamp recordings indicate that both classes of receptor are able to elicit inward currents that are totally blocked by d-tubocurarine but only partially blocked by alpha-bungarotoxin. In IMR32 cells, nicotine induces an increase in the intracellular level of free Ca2+. This increase, which is also completely blocked by d-tubocurarine and only partially blocked by alpha-bungarotoxin and Cd2+, is due to extracellular calcium influx through both the nicotinic receptors and the voltage-activated Ca2+ channels. By using subunit-specific polyclonal antibodies, we have demonstrated that the alpha-bungarotoxin receptors contain the alpha 7 subunit, but none of the other subunits whose transcripts are present in IMR32 cells. The pharmacological profile of these human alpha 7-containing alpha-bungarotoxin receptors is similar to that observed in the native chick alpha 7 receptor, but there are also some species-specific differences.
CNR Center of Cytopharmacology, Department of Medical Pharmacology, University of Milan, Italy.
C
C
Gotti
L
L
Briscini
C
C
Verderio
M
M
Oortgiesen
B
B
Balestra
F
F
Clementi
D000906:Antibodies / Q000276:immunology; D001667:Binding, Competitive; D002038:Bungarotoxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004586:Electrophoresis; D016257:Fura-2; D006801:Humans; D009447:Neuroblastoma; D018408:Patch-Clamp Techniques; D011869:Radioligand Assay; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000276:immunology* / Q000502:physiology*
D000906:Antibodies; D002038:Bungarotoxins; D011978:Receptors, Nicotinic; D002118:Calcium; D016257:Fura-2