Biomaterial Database

Calcium regulation of agonist binding to alpha7-type nicotinic acetylcholine receptors in adult and fetal rat hippocampus. 1998

J A Ospina, and R S Broide, and D Acevedo, and R T Robertson, and F M Leslie

Department of Pharmacology, College of Medicine, University of California, Irvine 92697, USA.

Quantitative autoradiography was used to compare the binding properties of alpha7-type nicotinic acetylcholine receptors in fetal and adult rat hippocampus. Whereas there were high levels of 125I-alpha-bungarotoxin (125I-alpha-BTX) binding throughout fetal hippocampal field CA1, there was a significant decrease in binding site density in the adult. The affinity of 125I-alpha-BTX binding, as well as alpha-cobratoxin and nicotine potency to displace 125I-alpha-BTX, did not change with age. Addition of Ca2+ to the assay buffer did not alter 125I-alpha-BTX binding, or alpha-cobratoxin inhibition of 125I-alpha-BTX binding, although it significantly increased nicotine affinity at both ages. The effect of Ca2+ on agonist affinity was dose-dependent, with an EC50 value of 0.25-0.5 mM. Ca2+ also significantly increased the cooperativity of nicotine displacement curves in stratum oriens of the adult, but not in the fetus. These findings indicate that the properties of hippocampal 125I-alpha-BTX binding sites are largely similar across age. Ca2+ selectively enhances the affinity of agonist binding, with no change in antagonist binding. This ionic effect may result from potentiation of agonist binding to a desensitized state of the alpha7 nicotinic acetylcholine receptor and may represent an important neuroprotective mechanism.

UI	MeSH Term	Description	Entries
D007457	Iodine Radioisotopes	Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes.	Radioisotopes, Iodine
D011978	Receptors, Nicotinic	One of the two major classes of cholinergic receptors. Nicotinic receptors were originally distinguished by their preference for NICOTINE over MUSCARINE. They are generally divided into muscle-type and neuronal-type (previously ganglionic) based on pharmacology, and subunit composition of the receptors.	Nicotinic Acetylcholine Receptors,Nicotinic Receptors,Nicotinic Acetylcholine Receptor,Nicotinic Receptor,Acetylcholine Receptor, Nicotinic,Acetylcholine Receptors, Nicotinic,Receptor, Nicotinic,Receptor, Nicotinic Acetylcholine,Receptors, Nicotinic Acetylcholine
D002038	Bungarotoxins	Neurotoxic proteins from the venom of the banded or Formosan krait (Bungarus multicinctus, an elapid snake). alpha-Bungarotoxin blocks nicotinic acetylcholine receptors and has been used to isolate and study them; beta- and gamma-bungarotoxins act presynaptically causing acetylcholine release and depletion. Both alpha and beta forms have been characterized, the alpha being similar to the large, long or Type II neurotoxins from other elapid venoms.	alpha-Bungarotoxin,beta-Bungarotoxin,kappa-Bungarotoxin,alpha Bungarotoxin,beta Bungarotoxin,kappa Bungarotoxin
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D005333	Fetus	The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.	Fetal Structures,Fetal Tissue,Fetuses,Mummified Fetus,Retained Fetus,Fetal Structure,Fetal Tissues,Fetus, Mummified,Fetus, Retained,Structure, Fetal,Structures, Fetal,Tissue, Fetal,Tissues, Fetal
D006624	Hippocampus	A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.	Ammon Horn,Cornu Ammonis,Hippocampal Formation,Subiculum,Ammon's Horn,Hippocampus Proper,Ammons Horn,Formation, Hippocampal,Formations, Hippocampal,Hippocampal Formations,Hippocampus Propers,Horn, Ammon,Horn, Ammon's,Proper, Hippocampus,Propers, Hippocampus,Subiculums
D000367	Age Factors	Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.	Age Reporting,Age Factor,Factor, Age,Factors, Age
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001345	Autoradiography	The making of a radiograph of an object or tissue by recording on a photographic plate the radiation emitted by radioactive material within the object. (Dorland, 27th ed)	Radioautography
D001667	Binding, Competitive	The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.	Competitive Binding