Modulation of the nicotinic alpha-bungarotoxin site in chromaffin cells in culture by a factor(s) endogenous to neuronal tissue.
An endogenous factor(s) which affects the in vitro binding of (alpha-BGT) to rat brain membranes has previously been found in brain supernatant. This fraction, as well as a partially purified preparation of this material from bovine brain, is here shown to affect the binding of alpha-BGT to chromaffin cell membranes. To study possible long term effects, the supernatant extract was added to adrenal medullary chromaffin cells in culture. The cells were incubated for several days and at the end of this time, the medium bathing the cells, which contained the endogenous factor(s), was removed and alpha-BGT binding to the cells measured. Binding to control cultures had shown that alpha-BGT bound to the chromaffin cells in a saturable manner, with high affinity (Kd = 1.5 nM) and the specificity of a nicotinic receptor ligand. After incubation of the cells with supernatant factor, a marked decline in the number of alpha-BGT binding sites was observed with no change in affinity. This does not appear to be due to a detrimental effect on the cells as cell number did not appear to be decreased in the cultures preincubated with the supernatant extract and the DNA and protein content were similar in the control and treated cultures. The possibility that there was some non-specific detrimental effect to the chromaffin cell membrane was considered; however, the stimulated release of noradrenaline from the cells was not affected by treatment of the cultures in the presence of the supernatant fractions. In addition, tyrosine hydroxylase activity was significantly increased in the treated cultures. D-Tubo-curarine, an antagonist at the acetylcholine receptor, caused an increase in alpha-BGT binding after 7 days of treatment, while the agonist nicotine and choline had no effect. These results suggest that in brain supernatant there may exist an endogenous factor(s), which may function in the regulation of the nicotinic-like alpha-BGT receptors in neuronal cell.
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D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002038:Bungarotoxins / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000302:isolation & purification / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000032:analysis* / Q000187:drug effects; D011978:Receptors, Nicotinic; D013997:Time Factors; D014020:Tissue Extracts / Q000378:metabolism; D014403:Tubocurarine / Q000494:pharmacology; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; C579165:Chrna7 protein, rat; D009419:Nerve Tissue Proteins; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D014020:Tissue Extracts; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; D002794:Choline; D014403:Tubocurarine