Dopamine increases Na+ absorption in the Reissner's membrane of the gerbil cochlea.
OBJECTIVE
The purpose of the present study was to investigate the effect of dopamine as a possible regulator of epithelial Na(+) channel (ENaC) in the Reissner's membrane (RM).


METHODS
RM was freshly dissected from the gerbil cochlea, and short-circuit current (Isc) was measured using the voltage-sensitive vibrating probe technique. The dopamine receptor expression was examined using immunohistochemistry.


RESULTS
The results showed that dopamine induced activation of the amiloride-sensitive Isc, but not after pre-treatment with amiloride. The D1-like receptor antagonist SCH-23390, but not the D2-like receptor antagonist sulpiride, decreased the stimulatory effect of dopamine on RM. The effect of dopamine on Na(+) transport via ENaC was still observed after blockade of the Na(+)-K(+)-ATPase by ouabain. D1 receptor immunoreactivity was observed in RM, stria vascularis and spiral ganglion.


CONCLUSIONS
Na(+) transport in RM is activated by dopamine possibly via D1-like receptors, and intracellular mechanisms other than cAMP-mediated pathway may be involved.
Department of Otorhinolaryngology-Head and Neck Surgery, Konkuk University School of Medicine, Republic of Korea.
Chang-Hee
CH
Kim
Hye-Young
HY
Kim
Ho Sun
HS
Lee
Byung Yoon
BY
Choi
Sun O
SO
Chang
Seung-Ha
SH
Oh
Jun Ho
JH
Lee
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D003051:Cochlea / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology*; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D062686:Epithelial Sodium Channel Blockers / Q000494:pharmacology; D053503:Epithelial Sodium Channels / Q000378:metabolism; D005849:Gerbillinae; D007150:Immunohistochemistry; D008566:Membranes / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011954:Receptors, Dopamine / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013469:Sulpiride / Q000494:pharmacology
D001552:Benzazepines; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D011954:Receptors, Dopamine; C534628:SCH 23390; D015124:8-Bromo Cyclic Adenosine Monophosphate; D010042:Ouabain; D000584:Amiloride; D013469:Sulpiride; D012964:Sodium; D004298:Dopamine