[The effect of nimodipine on cochlear blood flow in the guinea pig]. / Beeinflussung der kochleären Durchblutung des Meerschweinchens durch Nimodipin.

The influence of nimodipine (Nimotop, CAS 66085-59-4), a selectively cerebrovascularly acting 1,4-dihydropyridine calcium antagonist, on the cochlear blood flow (CBF) was studied in 19 guinea pigs (6 controls). The hydrogen clearance measurements were carried out under alpha-chloralose-ethylurethane anaesthesia, artificial respiration with simultaneous control of electrocardiogram, blood pressure, body temperature and arterial pH (hourly). The indirect measurement of CBF was carried out by means of hydrogen clearance in the perilymphatic space (basal turn) before and after intravenous application of 1 microgram nimodipine/kg/min. The mean arterial blood pressure remained within the +/- 5% range of the initial value during the experiment. Under treatment with nimodipine the CBF showed a non-significant average increase of 4.69% and under placebo (20% ethanol, 17% polyethylenglycol 400, citrate buffer), a non-significant average decrease of 6.16%. The influence of nimodipine on CBF was underlined by the overcompensation of the placebo effect.

[Inner ear blood flow with betahistine--an animal experiment study]. / Die Innenohrdurchblutung unter Betahistin-eine tierexperimentelle Studie.

The influence of the drug Betahistin on the cochlear blood flow (CBF) was checked on 15 guinea pigs (6 controls) (Charles River, BFA 350-450 g) by means of the hydrogen clearance method. The hydrogen clearance measurements were carried out under alpha-chloralose-ethylurethane anaesthesia, artificial respiration with simultaneous control of the electrocardiogram, arterial blood pressure and body temperature. The actual arterial pH-value was checked hourly. Indirect measurement of CBF was carried out in the perilymphatic space (basal turn) before and after intravenous application of Betahistin (vena jugularis externa) (dosage: 0.11 mg/kg/min). The mean arterial blood pressure remained within the 10% range during the experiments. Under Betahistin-treatment the CBF showed an significant increase (p = 0.05). Despite this favourable pharmacological efficiency of Betahistin it must be pointed out that the general application of vasoactive drugs, especially of vasodilative drugs, in the treatment of postulated inner ear blood flow disturbances is presently controversial.

The influence of military low-altitude flight noise on the inner ear of the guinea pig. Part I: Hearing threshold measurements.

The auditory thresholds of about 60 anaesthetized guinea pigs were determined at 3 or 4 frequencies between 2 and 20 kHz using the acoustically evoked brain stem potentials. The animals were then exposed to electro-acoustically reproduced MLAF noise with peak levels between 120 and 130 dB(A). The exposure occurred either once or else four times within either 3 or 60 minutes. The level of noise increased at 7.5 and 75 dB/s (slow and fast increase). TTS was then determined. PTS was measured one week later. In over half the animals, exposure to rapidly increasing noise level with a peak of 126 dB(A) induced PTS > or = 30 dB for at least one frequency. Exposure to a slowly increasing noise level with the same peak provoked significantly smaller PTS. 4 exposures to a rapidly rising noise level within 3 minutes induced significantly smaller PTS than the same dosage within 60 minutes. Only in the latter case was PTS greater than TTS.

Guinea pig cochlear blood flow under definite sound exposure-hydrogen clearance measurement.

Blood flow measurements were carried out on 18 coloured guinea pigs (8 animals served as control group) before and during definite sound exposure (12 kHz, 110 dB SPL). The exposure time amounted to 60 min. The anaesthesia was carried out according to the following schedule: a mixture consisting of 70 mg alpha-chloralose/kg b.w. and 400 mg urethane/kg b.w. was injected intraperitoneally. The relaxation was performed by means of i.p. application of 3 mg Tricuran/kg b.w./h. The hydrogen clearance measurements (HCM) were carried out under artificial respiration with control of arterial pH, endexpiratory CO2 content, as well as blood pressure and body temperature. After a duration of noise exposure of 30-45 min the cochlear blood flow reached an average level of 80% of the initial point. This level remained mainly unchanged until the end of noise exposure (60 min). Our HMC's confirm Laser Doppler flowmetry findings.

[On the secretion pressure of the human parotid gland (author's transl)]. / Uber den Sekretionsdruck der Glandula parotis des Menschen

The secretion pressure as well as the speed of resorption for saliva and water in the parotid gland is studied by electromanometry in 40 male and 14 female healthy persons on stop-flow conditions in rest and after gustatory stimulation with lemon juice. The course of intraglandular pressure after stoppage and retrograde instillation of pure water is demonstrated by typical diagrams. The essentials are discussed. The mutual relations of the measured parameters and those existing with the age are examined by means of simple correlation and linear regression analysis. Results of this analysis show that the pressure of resting secretion diminishes due to increasing age. With increasing secretory activity of the parotid gland the speed of intraglandular resorption increases, too. Pure water with be resorpted more quickly than saliva. Sex differences are not existing.