Differential effects of chronic drug treatment on alpha3* and alpha7 nicotinic receptor binding sites, in hippocampal neurones and SH-SY5Y cells.
1. The aim of this study was to compare the effects of chronic treatment (for 4 or 7 days) with nicotinic drugs and 20 mM KCl on numbers of surface alpha7 nicotinic AChR, identified by [(125)I]-alpha bungarotoxin (alpha-Bgt) binding, in primary hippocampal cultures and SH-SY5Y cells. Numbers of alpha3* nicotinic AChR were also examined in SH-SY5Y cells, using [(3)H]-epibatidine, which is predicted to label the total cellular population of predominantly alpha3beta2* nicotinic AChR under the conditions used. 2. All the nicotinic agonists examined, the antagonists d-tubocurarine and methyllycaconitine, and KCl, upregulated [(125)I]-alpha Bgt binding sites by 20 - 60% in hippocampal neurones and, where examined, SH-SY5Y cells. 3. Upregulation of [(125)I]-alpha-Bgt binding sites by KCl was prevented by co-incubation with the L-type Ca2+ channel blocker verapamil or the Ca2+-calmodulin dependent kinase II (CaM-kinase II) inhibitor KN-62. Upregulation of [(125)I]-alpha-Bgt binding sites by nicotine or 3,[(4-dimethylamino) cinnamylidene] anabaseine maleate (DMAC) was insensitive to these agents. 4. [(3)H]-Epibatidine binding sites in SH-SY5Y cells were not affected by KCl but were upregulated in a verapamil-insensitive manner by nicotine and DMAC. KN-62 itself provoked a 2 fold increase in [(3)H]-epibatidine binding. The inactive analogue KN-04 had no effect, suggesting that CaM-kinase II plays a role in regulating numbers of alpha3* nicotinic AChR. 5. These data indicate that numbers of alpha3* and alpha7 nicotinic AChR are modulated differently. Nicotinic agonists and KCl upregulate alpha7 nicotinic AChR through distinct cellular mechanisms, the latter involving L-type Ca2+ channels and CaM-kinase II. In contrast, alpha3* nicotinic AChR are not upregulated by KCl. This difference may reflect the distinct physiological roles proposed for alpha7 nicotinic AChR.
Ridley
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DL
Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY.
Rogers
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A
Wonnacott
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D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001392:Azocines; D001427:Bacterial Toxins / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D002038:Bungarotoxins / Q000378:metabolism; D002478:Cells, Cultured; D000087522:Cyanobacteria Toxins; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008387:Marine Toxins / Q000494:pharmacology; D052998:Microcystins; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009538:Nicotine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D011725:Pyridines / Q000378:metabolism; D011807:Quinolizines; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*; D014403:Tubocurarine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology; D064569:alpha7 Nicotinic Acetylcholine Receptor; D000093843:Quinolizidine Alkaloids
D000470:Alkaloids; D001392:Azocines; D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002038:Bungarotoxins; D000087522:Cyanobacteria Toxins; D004246:Dimethylphenylpiperazinium Iodide; D008387:Marine Toxins; D052998:Microcystins; D009538:Nicotine; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011725:Pyridines; D011807:Quinolizines; D011978:Receptors, Nicotinic; D014403:Tubocurarine; D014700:Verapamil; D064569:alpha7 Nicotinic Acetylcholine Receptor; C579167:Chrna7 protein, human; C579165:Chrna7 protein, rat; C004712:cytisine; D000093843:Quinolizidine Alkaloids; C082748:epibatidine