Gender Differences in Myogenic Regulation along the Vascular Tree of the Gerbil Cochlea

Abstract

Regulation of cochlear blood flow is critical for hearing due to its exquisite sensitivity to ischemia and oxidative stress. Many forms of hearing loss such as sensorineural hearing loss and presbyacusis may involve or be aggravated by blood flow disorders. Animal experiments and clinical outcomes further suggest that there is a gender preference in hearing loss, with males being more susceptible. Autoregulation of cochlear blood flow has been demonstrated in some animal models in vivo, suggesting that similar to the brain, blood vessels supplying the cochlea have the ability to control flow within normal limits, despite variations in systemic blood pressure. Here, we investigated myogenic regulation in the cochlear blood supply of the Mongolian gerbil, a widely used animal model in hearing research. The cochlear blood supply originates at the basilar artery, followed by the anterior inferior cerebellar artery, and inside the inner ear, by the spiral modiolar artery and the radiating arterioles that supply the capillary beds of the spiral ligament and stria vascularis. Arteries from male and female gerbils were isolated and pressurized using a concentric pipette system. Diameter changes in response to increasing luminal pressures were recorded by laser scanning microscopy. Our results show that cochlear vessels from male and female gerbils exhibit myogenic regulation but with important differences. Whereas in male gerbils, both spiral modiolar arteries and radiating arterioles exhibited pressure-dependent tone, in females, only radiating arterioles had this property. Male spiral modiolar arteries responded more to L-NNA than female spiral modiolar arteries, suggesting that NO-dependent mechanisms play a bigger role in the myogenic regulation of male than female gerbil cochlear vessels.

Ryanodine-induced vasoconstriction of the gerbil spiral modiolar artery depends on the Ca2+ sensitivity but not on Ca2+ sparks or BK channels

“…7). This finding is consistent with the development of small myogenic tones with increasing intravascular pressures in the SMA [12]. Rho-kinase-dependent regulation of Ca 2+ sensitivity also plays a significant role in mediating the vascular effects of endogenous vasoconstrictors and agonists [41–43].…”

“…Segments of the SMA were pressurized and perfused in a custom-built bath chamber using a variable hydrostatic pressure column connected to a motorized set of concentric glass pipettes (Wangemann Instruments, Kansas State University, KS) mounted on an inverted microscope (Axiovert 200, Carl Zeiss, Göttingen, Germany) [12]. Briefly, arteries were held by a holding pipette and luminally perfused with a perfusion pipette at one end while the other end was occluded using a blunt glass pipette.…”

“…In addition to filtering and recording fluorescence emissions as described above, the transmitted light from the argon laser was detected by a second photomultiplier. Inner diameter was measured by automatic edge detection by a method developed and described in Reimann et al 2011 [12]. Inner diameter (ID) was detected from acquired real time transmitted light images, using a custom written data acquisition program (Dr.…”

White Matter Hyperintensities Predict Low Frequency Hearing in Older Adults

“…For example, women can exhibit smaller and less compliant carotid and vertebral arteries (Hansen et al 1995;Gatzka et al 2001). In addition, the modiolar branches of the cochlear artery that support the stria vascularis are controlled by nitric oxide in male but not female gerbils (Reimann et al 2011), suggesting that the stria vascularis is at greater risk for ischemia and hemorrhage in females when atherosclerosis increases blood pressure in vessels that have limited autoregulation. A gradual decline in the stria vascularis, due to chronic hypertension that produces leaky vessels and that also would produce WMH, could therefore account for the results of the current study and a finding of low frequency hearing loss and retinopathy in women (Torre et al 2005).…”

Arteriolar vascular smooth muscle cells: Mechanotransducers in a complex environment

“…For example, cerebral and coronary vasospasms are important pathophysiological events suggested to be linked to abnormalities of mechanotransduction (Cipolla et al, 1997). Altered myogenic tone has also been implicated in the microvascular complications of diabetes (Hill and Ege, 1994), hypertension (Ahn et al, 2007), heart failure (Xu et al, 2009) and hearing disturbances (Reimann et al, 2011). Further, alterations in myogenic responsiveness may contribute to hypoperfused states such as occurs in sepsis (Meziani et al, 2007).…”