Initial characterization of the nicotinic acetylcholine receptors in rat hippocampal neurons.
The properties of the neuronal nicotinic acetylcholine receptor in primary cultures of hippocampal cells from fetal rats (17-18 days gestation) were studied using the whole-cell patch-clamp technique in Na(+)-external, Cs(+)-internal and nominally Mg(2+)-free solutions. The nicotinic agonists acetylcholine, (+)anatoxin-a, and (-) and (+)nicotine all evoked inward whole-cell currents in hippocampal neurons that were voltage clamped near their resting potentials. Sensitivity to (+)anatoxin-a was first detected at around day 6, and thereafter the magnitude of the response increased as a function of number of days in culture up to about 40 days. The whole-cell current waveforms consisted of more than one peak whose relative amplitude depended on the agonist concentration. These currents were reversibly blocked by micromolar concentrations of d-tubocurarine, mecamylamine, and dihydro-beta-erythroidine. At nanomolar concentrations, neuronal bungarotoxin, alpha-bungarotoxin and alpha-cobratoxin caused an irreversible blockade of the currents but they were unaffected by tetrodotoxin, atropine, DL-2-amino-5-phosphonovaleric acid, Mg2+, and 6,7-dinitroquinoxaline-2,3-dione. In addition, the currents were also blocked in a reversible manner by methyllycaconitine at picomolar concentration. The current-voltage plots elicited by both (+)anatoxin-a and acetylcholine revealed larger inward currents and smaller or no outward currents. The present results demonstrate the existence of an inwardly rectifying, snake neurotoxin-sensitive functional nicotinic acetylcholine receptor ion channel in rat hippocampal neurons.
Alkondon
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Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201.
Albuquerque
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D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology; D002478:Cells, Cultured; D005260:Female; D006624:Hippocampus / Q000737:chemistry* / Q000187:drug effects; D009474:Neurons / Q000737:chemistry*; D010276:Parasympatholytics / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011978:Receptors, Nicotinic / Q000032:analysis* / Q000187:drug effects / Q000502:physiology
D002038:Bungarotoxins; D010276:Parasympatholytics; D010277:Parasympathomimetics; D011978:Receptors, Nicotinic