[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.

Heart rate variability in diabetic patients during orthostatic load--a spectral analytic approach.

Spectral analysis of heart rate variability (HRV) was used to assess the autonomic nervous control of cardiac function during orthostatic load in insulin-dependent diabetic patients and healthy subjects. The diabetic patients were divided into three groups: diabetics without neuropathy (group 1), diabetics with peripheral neuropathy (group 2), and diabetics with peripheral and autonomic neuropathy (group 3). Resting mid-frequency (MF, 0.05-0.15 Hz) and respiration-related (RF, power around respiration rate) HRV were significantly lower in group 2 and 3 diabetics than in controls, indicating a reduced parasympathetic nervous system influence on the heart. Standing MF and RF spectral power data were significantly lower in all diabetic groups than in controls, suggesting marked alterations in the autonomic cardiovascular control during a mild physical load not only in symptomatic diabetics but also in patients with no signs and symptoms of neuropathy. The difference between supine and standing MF power, an estimate of beta-adrenergic influence on the heart, was significantly lower in all diabetic subject groups studied than in controls. This suggests a reduced sympathetic nervous system influence on the heart in diabetic patients. Our data suggest that computerized spectral analysis of HRV during orthostatic load seems to be a very sensitive method of evaluating of the autonomic nervous systems influence on the heart in patients suffering from diabetes mellitus.

[An animal model of surgical, external cardiac denervation. Studies of the autonomic control of heart rate]. / Tiermodell der operativen, externen kardialen Denervierung Untersuchungen zur neurovegetativen Herzfrequenzsteuerung.

A great role is played in clinical practice by monitoring of vegetative functions, such as heart and respiratory rates. Mean values, rhythms, and interaction of both control variables in the form of respiratory sinus arrhythmia may provide plenty of information, primarily when computerised, and may enable conclusions to be drawn as to neuro-circulatory tonus. The model described in this paper has been devised for the purpose of producing information on types of changes in neurovegetative control in response to functional systemic effects from pharmaceuticals or from substantial, locally delimited lesions of nerve structures. External cardiac denervation is applied for stepwise discontinuation of sympathetic, parasympathetic, spinal, and medullary control systems up to the stage of cerebral death, resulting in cardiac "automatism". Data may thus be derived on the Bainbridge reflex, and correlations may be established with in vitro experiments on chronotropic control of the heart. The results presented in this paper may be of relevance to situations in intensive medical care or to cases with lesions to the central nervous system up to irreversible loss of brain function, when heart rate data recorded from monitoring of the central nervous system or of vegetative functions must be interpreted in all their variability with high reliability and accuracy for differential diagnosis and prognostication.