Muscarinic acetylcholine receptors in the brain of the zebrafish(Danio rerio)measured by radioligand binding techniques

摘要

Muscarinic acetylcholine receptors(mAChRs)play a role in learning,memory and behavior in vertebrate animals.We measured the muscarinic cholinergic receptor levels in extracts from zebrafish(Danio rerio)brain by radioligand binding techniques.Saturation binding experiments with the radioligand [~3H]-quinuclidinyl benzilate(QNB)were used to determine receptor number and relative affinity for several agonists and antagonists.Affinity at zebrafish brain receptors was relatively high with a K_d of 40(+-)5 pM.The number of receptors,represented by S_max,was 63(+-)16 fmol/mg protein.Oxotremorine and carbachol,agonists at muscarinic acetylcholine receptors,bound with displacement curves indicating multiple binding sites.In addition,oxotremorine bound with a higher affinity than did carbachol.The antagonist potency profile at zebrafish receptors in brain was determined to be atropinepirenzipine>p-fluoro-hexahydro-sila-difenidolotenzepad.The results obtained with zebrafish brain compare favorably to those found in insect,fish and mammalian species.Taken together,the binding results and favorable comparisons to mammalian systems indicate that zebrafish may provide a useful model organism for evaluating the role of cholinergic systems in learning,memory and behavior.