Immunohistochemical localization of histamine receptors in rat cochlea.
OBJECTIVE
Histamine may have physiologic functions in the inner ear. The locations of histamine receptors, however, have not yet been identified in the mammalian cochlea. The aim of this study was to investigate the localization of histamine receptor subtypes (H1, H2, and H3 receptors) in rat cochlea.


METHODS
Immunohistochemistry was performed with antibodies specific for each of the histamine receptors (H1, H2, and H3). To identify the type I and II spiral ganglion cells in the cochlea, some cryostat sections were double stained with antibodies to both a histamine receptor and neurofilament 200 kD, which predominantly stains type II spiral ganglion cells in the cochlea.


RESULTS
All H1, H2, and H3 receptor immunoreactive staining was limited to the spiral ganglion cells of the cochlea. Spiral ganglion cells with positive immunoreactivity to the neurofilament 200 kD antibody were stained only slightly by histamine H1, H2, and H3 receptor antibodies, indicating that histamine receptor immunoreactivity is specific to type I ganglion cells.


CONCLUSIONS
These findings indicate that histamine receptors are present in the cochlea and support the hypothesis that histamine plays a physiologic role in the cochlea.
Azuma
Hiroshi
H
Department of Otolaryngology, Kochi Medical School, Nankoku, Kochi, Kohasu, Okocho, Nankoku, Kochi 783-8505, Japan. azuma@kochi-ms.ac.jp
Sawada
Shoichi
S
Takeuchi
Shunji
S
Higashiyama
Kasumi
K
Kakigi
Akinobu
A
Takeda
Taizo
T
D000818:Animals; D003051:Cochlea / Q000033:anatomy & histology* / Q000648:ultrastructure*; D005260:Female; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D023421:Models, Animal; D051381:Rats; D017208:Rats, Wistar; D011968:Receptors, Histamine / Q000032:analysis*; D011969:Receptors, Histamine H1 / Q000032:analysis; D011970:Receptors, Histamine H2 / Q000032:analysis; D018100:Receptors, Histamine H3 / Q000032:analysis; D012680:Sensitivity and Specificity
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D018100:Receptors, Histamine H3