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Two distinct classes of functional α7‐containing nicotinic receptor on rat superior cervical ganglion neurons
Author(s) -
Cuevas Javier,
Roth Adelheid L.,
Berg Darwin K.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.t01-1-00735.x
Subject(s) - methyllycaconitine , superior cervical ganglion , nicotinic agonist , acetylcholine receptor , chemistry , acetylcholine , sympathetic ganglion , neuroscience , biophysics , biology , receptor , medicine , endocrinology , nicotinic acetylcholine receptor , biochemistry
1 Nicotinic acetylcholine receptors (nAChRs) that bind α‐bungarotoxin (αBgt) were studied on isolated rat superior cervical ganglion (SCG) neurons using whole‐cell patch clamp recording techniques. 2 Rapid application of ACh onto the soma of voltage clamped neurons evoked a slowly desensitizing current that was reversibly blocked by αBgt (50 n m ). The toxin‐sensitive current constituted on average about half of the peak whole‐cell response evoked by ACh. 3 Nanomolar concentrations of methyllycaconitine blocked the αBgt‐sensitive component of the ACh‐evoked current as did intracellular dialysis with an anti‐α7 monoclonal antibody. The results indicate that the slowly reversible toxin‐sensitive response elicited by ACh arises from activation of an unusual class of α7‐containing receptor (α7‐nAChR) similar to that reported previously for rat intracardiac ganglion neurons. 4 A second class of functional α7‐nAChR was identified on some SCG neurons by using rapid application of choline to elicit responses. In these cases a biphasic response was obtained, which included a rapidly desensitizing component that was blocked by αBgt in a pseudo‐irreversible manner. The pharmacology and kinetics of the responses resembled those previously attributed to α7‐nAChRs in a number of other neuronal cell types. 5 Experiments measuring the dissociation rate of 125 I‐labelled αBgt from SCG neurons revealed two classes of toxin‐binding site. The times for toxin dissociation were consistent with those required to reverse blockade of the two kinds of αBgt‐sensitive response. 6 These results indicate that rat SCG neurons express two types of functional α7‐nAChR, differing in pharmacology, desensitization and reversibility of αBgt blockade.