Cholinergic influence on vestibular stimulation-induced locus coeruleus inhibition in rats.
In our previous study, caloric stimulation (CS) of the vestibular apparatus inhibited noradrenergic neuronal activity in the locus coeruleus (LC) in urethane-anaesthetized rats. Therefore, the inhibition of LC noradrenergic neurons is involved in vestibulo-autonomic responses. Since motion sickness can be cured by scopolamine, cholinergic neuron system may also be involved in vestibulo-autonomic responses. The present study examined the effects of intracerebroventricular injection of ethylcholine mustard aziridinium ion (AF64A), a presynaptic cholinergic neurotoxin, on CS-induced LC inhibition. In AF64A-treated rats, the CS-induced LC inhibition was less pronounced than in normal rats. In a subsequent series of experiments, the intravenous injection of scopolamine blocked the CS-induced LC inhibition. These findings suggest that central cholinergic neurons are associated with noradrenergic neuronal inhibition during the vestibulo-autonomic reflex.
Nishiike
S
S
Department of Otolaryngology, Osaka University Medical School, Suita, Japan.
Takeda
N
N
Uno
A
A
Kubo
T
T
Yamatodani
A
A
Nakamura
S
S
D000818:Animals; D001388:Aziridines / Q000009:adverse effects; D002150:Caloric Tests / Q000379:methods*; D002794:Choline / Q000009:adverse effects / Q000031:analogs & derivatives; D002799:Cholinergic Fibers / Q000187:drug effects*; D004195:Disease Models, Animal; D004567:Electrodes, Implanted; D008125:Locus Coeruleus / Q000187:drug effects* / Q000503:physiopathology*; D008297:Male; D009041:Motion Sickness / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology; D018727:Muscarinic Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D009466:Neuromuscular Blocking Agents / Q000009:adverse effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012601:Scopolamine / Q000494:pharmacology / Q000627:therapeutic use; D013997:Time Factors; D014722:Vestibule, Labyrinth / Q000187:drug effects / Q000503:physiopathology*
D001388:Aziridines; D018727:Muscarinic Antagonists; D009466:Neuromuscular Blocking Agents; C044894:ethylcholine aziridinium; D012601:Scopolamine; D002794:Choline