Effect of electroacupuncture on arginine vasopressin-induced endolymphatic hydrops

To investigate the influence of electroacupuncture (EA) on experimentally induced endolymphatic hydrops (EH) in guinea pigs, and elucidate the association between the dehydrating effect of EA and changes in stria vascularis ultrastructure and expression of vasopressin type 2 receptor (V2R), cyclic adenosine monophosphate (cAMP), and aquaporin 2 (AQP2) in the endolymphatic sac (ES).

The EH model was established by intraperitoneal injection of arginine vasopressin (AVP). As a treatment, EA was delivered to Baihui (GV 20) and Tinggong (SI 19) acupoints, once daily for 10 consecutive days. For histomorphological studies, degree of cochlear hydrops was evaluated by hematoxylin-eosin staining, and the ratio of scala media (SM) area to SM + scala vestibuli area was calculated. In mechanical studies, ultrastructural changes in stria vascularis tissue were examined by transmission electron microscopy. In addition, cAMP levels and mRNA expression levels of V2R and AQP2 in the ES were compared among groups.

EA treatment significantly reduced cochlear hydrops compared with hydropic guinea pigs (P = 0.015). Furthermore, EA attenuated ultrastructural changes in the stria vascularis tissue following EH, significantly upregulated the expression of V2R (P = 0.016), and attenuated AVP-induced upregulation of both cAMP (P = 0.038) and AQP2 expression (P = 0.017) in the ES.

Collectively, the results of the present study suggest that the dehydrating effect of EA is associated with improvement of stria vascularis ultrastructure and V2R-cAMP-AQP2 signaling pathway regulation in the ES.