Autoregulation of cochlear blood flow in normotensive and spontaneously hypertensive rats following intracerebroventricularly mediated adjustment of blood pressure

Previous studies in our laboratory (Quirk et al., 1988) noted significantly impaired elevations in cochlear blood flow (CoBF) during systemic infusion of the potent vasoconstrictive agent angiotensin II (AII) in the spontaneously hypertensive rat (SHR) as compared with the normotensive Wistar-Kyoto (WKY) rat, despite similar increases in systemic blood pressure. We interpreted these results to suggest that SHRs have an exaggerated autoregulatory mechanism that controls blood supply to the cochlear vessels. However, an alternative explanation for these findings concerns the potential influence of the elevated baseline blood pressure of the SHR on CoBF. Specifically, if there is an absolute threshold blood pressure that triggers an autoregulatory response in the cochlea, then the SHRs would reach that threshold sooner than normotensive animals because they begin at a baseline blood pressure that is well above that of the WKY rat. The present study addressed this possibility by pharmacologically reducing SHR blood pressure to WKY baseline blood pressure and raising WKY to SHR baselines, followed by the infusion of previously utilized doses of AII. The results are consistent with previous findings and support our interpretation of an exaggerated autoregulation of cochlear blood supplying the SHR.     

Characteristics of temporary noise-induced tinnitus in male and female subjects

Reversible tinnitus was induced in 10 male and 8 female normal-hearing subjects following a 5 min 110 dB SPL exposure to white noise. Temporary threshold shift (TTS) was measured at 2 and 4 kHz. Characteristics of the tinnitus were determined by means of a written questionnaire administered 5 min following termination of the noise. Most of the subjects experienced a continuous tonal tinnitus of moderate loudness. Characterization of the tinnitus regarding spectral quality, type of sound, and perceived location differed as a function of gender. No difference in TTS measured at 2 and 4 kHz was seen as a function of gender. Positive relationships of fair to moderate strength were revealed between pre-exposure thresholds, TTS, and tinnitus pitch and level.     

Effects of hydroxyethyl starch, nimodipine, and propylene glycol on cochlear blood flow.

A primary goal of pharmacologic treatment for otopathologies of vascular origin is to elevate cochlear blood flow (CoBF), thus facilitating the transport of oxygen and nutrients without compromising perfusion pressure in other tissues. In the present investigation, significant increases in CoBF were measured during intra-arterial infusion of the plasma expanding agent, hydroxyethyline starch (HES), and the vasodilator nimodipine, in anesthetized adult male guinea pigs. There were no changes in systemic blood pressure during the infusion of HES or nimodipine. Intra-arterial infusion of propylene glycol (PG), which is used as a nonaqueous solvent, produced inconsistent CoBF effects accompanied by initial decreases in systemic blood pressure with subsequent increases. It is concluded that nimodipine and HES are very promising agents for inducing increases in CoBF, whereas PG produced inconsistent effects on CoBF while elevating blood pressure, thus compromising its potential usefulness in the treatment of otopathologies.     

Effects of perilymph volume adjustments on cochlear blood flow in the guinea pig

Previous research suggests a potential relationship between perilymphatic pressure (Pp) and cochlear blood flow (CBF); however, the alterations in Pp necessary to produce changes in CBF have not been adequately described or quantified. The effects of perilymph volume changes on systemic blood pressure (BP) and CBF were presently investigated in the guinea pig cochlea. Five microliters of perilymph were displaced in each of three conditions: viz. evacuation of 5 microliters from the cochlea; replacement of these 5 microliters; and finally the addition of 5 microliters of artificial perilymph into the cochlea. All perilymph volume adjustments were completed in 1-microliter increments during which changes in CBG and BP were recorded. Significant alterations in CBF were observed during 1-microliter perilymph volume adjustments in each condition with no significant changes in systemic BP. The results from this study support our hypothesis that an inverse relationship exists between CBF and Pp in that decreases in perilymph volume yielded elevations in CBF while increases in perilymph volume yielded reductions in CBF.     

Changes in pure-tone thresholds and temporary threshold shifts as a function of menstrual cycle and oral contraceptives

The present study examined the effects of exogenous and endogenous ovarian hormones on auditory functioning in young women. Fluctuations in pure tone thresholds and temporary threshold shifts (TTS) at 4 kHz and 6 kHz were assessed across the menstrual cycle. A group of normally cycling, ovulatory women and a group of women using Ortho Novum 7/7/7, a tri-phasic oral contraceptive, were tested during menstruation, at ovulation, and during the luteal phase of their menstrual cycle. A group of men served as controls and were tested at 3 similarly spaced intervals. Only the normally cycling women had significant cyclic fluctuations in auditory sensitivity, displaying poorer thresholds at 4 kHz during the menstrual phase than at the time of ovulation or during the luteal phase. In addition, normally cycling women were found to have significantly less TTS at 6 kHz during the menstrual phase than women using oral contraceptives.     

Comparison of mental health services in rural and urban Washington

Rural mental health has been an area of increased study in recent years because of unique problems in service of rural areas and underrepresentation of professionals in rural areas. This study collected information from mental health centers in the state of Washington via the state management information system. Rural/urban differences were examined. Results showed that (1) rural therapist were more likely to be generalists than urban therapists, (2) psychologists performed more of the direct service work in rural centers than they did in urban centers, (3) rural centers spent less time in direct activities, and more time in support activities, but did not differ from urban centers in indirect activities, and (4) rural and urban centers did not spend different percentages of time in specific direct, indirect, and support activities with the exception of day treatment where urban centers put more of their time than rural centers.     

The effects of nicotine on laser Doppler measures of cochlear blood flow

Anesthetized guinea pigs were given arterial bolus injections of saline or varying nicotine concentrations. Blood flow through the cochlea and skin were measured via laser Doppler and arterial blood pressure via an arterial cannula. Cochlear blood flow increased with low doses of nicotine but decreased with the highest dose, while blood pressure increased and skin flow decreased with all doses of nicotine. Control injections of saline vehicle had only minor and transient effects.     

Individual differences in response to alcohol. Vasoconstriction and vasodilation

Subjects who envidenced vasoconstriction after consuming alcohol did better than vasodilators on a simple motor task, but worse on more demanding tasks.     

The effects of pentoxifylline on cochlear blood flow in normotensive and spontaneously hypertensive rats

Normotensive and spontaneously hypertensive rats (SHRs) were given arterial infusions of saline and pentoxifylline in doses of 1.5, 2.0, and 3.0 mg/kg/min. Blood pressure decreased in a dose related fashion with increasing doses of pentoxifylline. Cochlear blood flow, measured via laser Doppler flowmeter, increased with infusion of pentoxifylline in members of both rat strains, but to a greater extent in SHRs than in normotensive animals. The mechanism of action appears to be decreased red blood cell rigidity which allows increased penetration of red blood cells into microvessels of the cochlea.