Endothelin-1 causes luminal constrictions in rat cochlear veins

The expression of VIP and SP in the cochlea of spontaneously hypertensive rats and its implication

To investigate the expression of vasoactive intestinal peptide (VIP) and substance P (SP) in the cochlea of spontaneously hypertensive rat (SHR), and to assess the function of VIP and SP in the cochlea following the damage of hypertension, hearing thresholds of ABR were observed and the fixative (4% paraformaldehyde) was pumped through the circulatory system. Adult Wistar rats (3 months, n=20) served as the control group and SHRs (3 months, n=20) as the hypertension group. Bullas were taken out and cochleas were irrigated in vitro with the same fixative. The number of base turn's spiral ganglions in the sections was counted. The expression of VIP and SP were detected by SABC method and the images of the sections were analyzed. The number of base turn's spiral ganglsons in the hypertension group was significantly less than in the normal group (P<0.01). VIP and SP were expressed in the spiral ganglion cytoplasma and stria vascularis of the two groups. There were no significant difference in the expression of VIP and SP in spiral ganglion cytoplasma (P>0.05) between the two groups. However, in stria vascularis the expression of VIP in the hypertension group was higher than in the normal group (P<0.05), and no significant difference in SP was found between the two groups. It was suggested that VIP not only contributed to the regulation of the cochlea microcirculation, but also made the neurotransmitter in the pathway of the auditory system. However, SP made only the neurotransmitter in the pathway of the auditory system.

Development and regression of cochlear blood vessels in fetal and newborn mice

Various strains of mice have been used for hearing research, but there have been few reports regarding the cochlear vasculature in mice. In this study, the development of the cochlear vasculature was investigated in C57BL/6 mice from day 15 of gestation to day 15 after birth, and mature vessels were also observed in 3-month-old mice. Both India ink injection and the resin casting method were used. On gestational day 17, spiral vessels of the basilar membrane were developing and were elaborating communicating branches that ran toward the external wall and the spiral lamina. On day 18, the spiral vessels showed the largest diameter of all vessels in the cochlea, but these vessels subsequently regressed and finally disappeared by day 14 after birth. The external wall vessels formed a single-layer capillary network at birth and subsequently divided into two layers, which became the vessels of the stria vascularis and the spiral ligament vessels. This process occurred progressively from the basal turn toward the apical turn between days 5 and 8 after birth. A general tendency for the cochlear vasculature to mature from the basal turn towards the apex was observed.