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Muscarinic Receptors in the Cochlear Nucleus and Auditory Nerve of the Guinea Pig
Author(s) -
Whipple Michael R.,
Drescher Dennis G.
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb06696.x
Subject(s) - dorsal cochlear nucleus , cochlear nucleus , muscarinic acetylcholine receptor , nucleus , chemistry , acetylcholine , neuroscience , quinuclidinyl benzilate , medicine , endocrinology , receptor , biology , biochemistry
The specific‐binding properties of l ‐[ 3 H]quinuclidinyl benzilate, a muscarinic acetylcholine‐receptor antagonist, were investigated in synaptic and other membrane preparations of the guinea pig cochlear nucleus and auditory nerve. Binding parameters for all experiments were consistent with a single binding site with a Hill coefficient of 1.0. The binding of the ligand was specific and of high affinity, with values of K D in the range of 30–80 p M . B max was 0.352 ± 0.023 pmol/mg protein for the dorsal cochlear nucleus and 0.215 ± 0.011 pmol/mg protein for the ventral cochlear nucleus. The dorsal cochlear nucleus/ventral cochlear nucleus ratio for density of muscarinic receptors (1.6/1.0) was maintained across two different buffer systems, which varied with respect to the inclusion of proteolysis inhibitors. The results for auditory nerve indicated a level of binding much below that of the cochlear nucleus, with B max = 0.052 ± 0.011 pmol/mg protein. The results of specific‐binding experiments for l ‐[ 3 H]quinuclidinyl benzilate support a role for acetylcholine as a neurotransmitter in the cochlear nucleus. The greater density of muscarinic receptors in the dorsal cochlear nucleus may indicate greater cholinergic activity in the dorsal relative to the ventral cochlear nucleus.