Evidence of a functional alpha7-neuronal nicotinic receptor subtype located on motoneurons of the dorsal motor nucleus of the vagus.
In vitro autoradiography using 125I-alpha-bungarotoxin (alpha-BGTx) and anti-alpha7 immunohistochemistry were performed on the dorsal motor nucleus of the vagus (DMV) of sham and chronically vagotomized rats to determine whether the alpha7-nicotinic acetylcholine receptor (nAChR) is located postsynaptically on DMV neurons whose axons contribute to the vagus nerve. Intense bilateral 125I-alpha-BGTx binding and anti-alpha7 immunostaining were observed in coronal brain sections containing the DMV of sham-vagotomized animals. Unilateral cervical vagotomy resulted in ipsilateral losses of 125I-alpha-BGTx binding and anti-alpha7 immunostaining from the DMV. Simultaneous staining of rat brainstem sections with anti-alpha7 and anti-choline acetyltransferase (ChAT) antibodies (to identify cholinergic DMV neurons that project into the vagus nerve) revealed that every DMV neuron that was stained for ChAT showed alpha7-staining as well. In vagotomized animals, no ChAT-positive neurons expressing alpha7-nAChRs remained in the ipsilateral DMV. We conclude that the alpha7-nAChR subtype is located postsynaptically on DMV neurons. To test whether the alpha7-nAChR is similar to the alpha7-homomeric nAChR, experiments were performed in anesthetized rats, and compounds were microinjected into the DMV while monitoring intragastric pressure (IGP). alpha-BGTx and strychnine antagonized nicotine-induced increases in IGP; no antagonism was observed with methyllycaconitine, a compound known to block the homomeric alpha7-nAChR subtype. Recovery from alpha-BGTx-induced antagonism of the nicotine response was observed. We conclude that there is a nAChR containing the alpha7-subunit in the DMV that is different from the homomeric alpha7-nAChR subtype.
Ferreira
M
M
Department of Pharmacology, Georgetown University School of Medicine, Washington, DC 20007, USA.
Ebert
S N
SN
Perry
D C
DC
Yasuda
R P
RP
Baker
C M
CM
Dávila-García
M I
MI
Kellar
K J
KJ
Gillis
R A
RA
D000157:Aconitine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D002038:Bungarotoxins / Q000493:pharmacokinetics / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate; D019084:Fluorescent Antibody Technique, Indirect; D008297:Male; D008845:Microinjections; D009046:Motor Neurons / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D013270:Stomach / Q000187:drug effects; D014628:Vagotomy; D014630:Vagus Nerve / Q000166:cytology / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; C579165:Chrna7 protein, rat; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; C054634:methyllycaconitine; D016650:Fluorescein-5-isothiocyanate; D000157:Aconitine