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Presynaptic muscarinic acetylcholine receptors suppress GABAergic synaptic transmission in the intermediate grey layer of mouse superior colliculus
Author(s) -
Li Fengxia,
Endo Toshiaki,
Isa Tadashi
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03668.x
Subject(s) - muscarine , neuroscience , methoctramine , chemistry , pirenzepine , muscarinic acetylcholine receptor , gabaergic , neurotransmission , acetylcholine , muscarinic acetylcholine receptor m2 , inhibitory postsynaptic potential , biology , endocrinology , receptor , biochemistry
The intermediate grey layer (the stratum griseum intermediale; SGI) of the superior colliculus (SC) receives cholinergic inputs from the parabrachial region of the brainstem. It has been shown that cholinergic inputs activate nicotinic acetylcholine (nACh) receptors on projection neurons in the SGI. Therefore, it has been suggested that they facilitate the initiation of orienting behaviours. In this study, we investigated the effect of muscarinic acetylcholine (mACh) receptor activation on GABAergic synaptic transmission to SGI neurons using the whole‐cell patch‐clamp recording technique in slice preparations from mice. The GABA A receptor‐mediated inhibitory postsynaptic currents (IPSCs) evoked in SGI neurons by focal electrical stimulation were suppressed by bath application of 10 µ m muscarine chloride. During muscarine application, both the paired‐pulse facilitation index and the coefficient of variation of IPSCs increased; however, the current responses induced by a transient pressure application of 1 m m GABA were not affected by muscarine. Muscarine reduced frequencies of miniature IPSCs (mIPSCs) while the amplitudes of mIPSCs remained unchanged. These results suggestd that mAChR‐mediated inhibition of IPSCs was of presynaptic origin. The suppressant effect of muscarine was antagonized by an M1 receptor antagonist, pirenzepine dihydrochloride (1 µ m ), and a relatively specific M3 receptor antagonist, 4‐DAMP methiodide (50 n m ). By contrast, an M2 receptor antagonist, methoctramine tetrahydrochloride (10 µ m ), was ineffective. These results suggest that the cholinergic inputs suppress GABAergic synaptic transmission to the SGI neurons at the presynaptic site via activation of M1 and, possibly, M3 receptors. This may be an additional mechanism by which cholinergic inputs can facilitate tectofugal command generation.