The Journal of Neuroscience, September 15, 1999, 19(18):7804-7811
Fast Excitatory Nicotinic Transmission in the Chick Lateral
Spiriform Nucleus
Yi
Nong,
Eva M.
Sorenson, and
Vincent A.
Chiappinelli
Department of Pharmacology, The George Washington University
Medical Center, Washington, DC 20037
The lateral spiriform nucleus (SpL) in the chick mesencephalon
contains functional nicotinic receptors and receives a cholinergic fiber projection. We now use double-label immunohistochemistry to
demonstrate that choline acetyltransferase-immunopositive fibers in the SpL and in the cholinergic fiber tract lateral to the nucleus are associated with fibers expressing the 
5 and/or 3 nicotinic receptor subunits as determined by mAb35 immunoreactivity. This morphological evidence suggests that there might be synapses between the cholinergic fibers and the dendrites of SpL neurons. Whole-cell recordings from SpL neurons in current-clamp mode revealed EPSPs evoked by stimulation of the cholinergic fiber tract lateral to the
SpL. These EPSPs increased in amplitude in the presence of bicuculline.
Further addition of the nicotinic antagonist dihydro-
-erythroidine (DHE) to the buffer significantly attenuated them. Almost all of the
remaining EPSP was blocked by 6,7-dinitroquinoxaline-2,3-dione. In the
presence of an antagonist cocktail that isolated the nicotinic responses, a fast, monosynaptic nicotinic EPSP or EPSC was
evoked. In some neurons, the nicotinic EPSP resulted in the generation of an action potential. The nicotinic nature of the evoked
response was confirmed by blockade of the EPSPs or EPSCs with nicotinic antagonists, including DHE, D-tubocurare, and
mecamylamine. The nicotinic response was insensitive to low
concentrations (10-100 nM) of methyllycaconitine,
indicating that typical 7-containing receptors were not involved.
The results demonstrate that endogenously released acetylcholine
generates EPSPs that can elicit action potentials by acting at
postsynaptic nicotinic receptors on SpL neurons.
Key words:
nicotinic; evoked; neurotransmission; lateral spiriform
nucleus; cholinergic; 5 nicotinic receptor subunit
Copyright © 1999 Society for Neuroscience 0270-6474/99/19187804-08$05.00/0
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