[A dopaminergic projection from the dorsal raphe nucleus to the inner ear].
OBJECTIVE
To investigate the efferent pathway from the dorsal raphe nucleus to the inner ear.


METHODS
Eleven adult cats weighing 2.0 - 3.0 kg were used. The animals had no middle-ear disease and their auricle reflex was sensitive to sound. They were divided into experimental group (8 cats) and control group (3 cases). The fluorescent tracer cholera toxin subunit-B (CTB) was injected into cat cochlea and the CTB-labelled neurons of dorsal raphe nucleus (DRN) were identified using an immunofluorescence technique after a survival period of 7 days. For studying other fluorescence labelling, the sections containing CTB-labelled neurons were divided into four groups and incubated in antisera directed against tyrosine hydroxylase (TH), serotonin (5-HT), gamma-aminobutyric acid (GABA) and dopamine B-hydroxylase (DBH), respectively. Single-and double-labelled neurons were identified from the DRN.


RESULTS
(1) A subpopulation of dorsal raphe nucleus (DRN) neurons were intensely labelled with CTB and these CTB-labelled neurons were densely distributed in a dorsomedial part of the DRN; (2) Four immunolabelling, TH, 5-HT, GABA and DBH were presented throughout the DRN. Of the total population of CTB-labelled neurons, 100% were TH-labelled neurons (double labelling) and no double-stained neuron with 5-HT, GABA and DBH was observed in the DRN.


CONCLUSIONS
There was a projection from DRN to the inner ear and this pathway might be a dopaminergic projection.
Yang
Xin-Ming
XM
Department of Otorhinolaryngology Head and Neck Surgery, Xiangya Second Hospital, Central South University, Changsha 410011, China. x16y2003@yahoo.com.cn
Wang
Shu-Hui
SH
Yang
Yi-Da
YD
Tang
Qing-Lai
QL
Zhang
Ting
T
Tan
Peng
P
Song
Ke-Ying
KY
Liu
Qiang-He
QH
D000818:Animals; D002415:Cats; D007758:Ear, Inner / Q000294:innervation* / Q000378:metabolism; D004525:Efferent Pathways; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D011903:Raphe Nuclei / Q000378:metabolism / Q000502:physiology*