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Biomedical subjects

G Kobal

Publications and source records attributed to G Kobal.

At least 109 records · Page 6Linked to original sources
PubMed1992

Chemosensory event-related potentials in the investigation of interactions between the olfactory and the somatosensory (trigeminal) systems.

The aim of the study was to investigate the interaction of the olfactory and somatosensory systems in the perception of chemical stimuli. Stimuli were chosen so as to selectively activate the olfactory (hydrogen sulphide, H2S) and trigeminal (carbon dioxide, CO2) nerves. In addition, carvone was included as a stimulus with mixed properties. Thirty healthy volunteers participated in the experiments. Subjects rated the intensity of each of the stimulants when presented alone and as a component of binary mixtures. Chemosensory event-related potentials (CSERPs) were obtained from 5 recording positions. Analysis of the intensity ratings indicated that there was no difference between the 3 stimulants when used as single components. In binary mixtures intensity estimates of H2S were suppressed by CO2 and carvone. In addition, while estimates of CO2 were suppressed by carvone estimates of the latter were enhanced in the same mixture. CSERP data confirmed earlier findings with regard to the topographic distribution of amplitudes, i.e., if the olfactory system had been activated largest amplitudes were observed at position Pz, whereas activation of the trigeminal nerve produced largest amplitudes at Cz. Moreover, the suppression of CO2 estimates by carvone was reflected in a corresponding suppression of the CSERP amplitudes. In addition, when CO2 was mixed with H2S or carvone there was a decrease in the CSERP latency indicating interactions of both sensory systems in the time domain.

Adolescent↗
PubMed1992

Pain in extracorporeal shock-wave lithotripsy: a comparison of different lithotripters in volunteers.

The aim of the present study was to investigate pain sensations experienced during extracorporeal shock-wave application, comparing an electrohydraulic (MPL 9000; Dornier Medizintechnik, Germering, Germany), an electromagnetic (Lithostar Plus; Siemens, Erlangen, Germany), and a piezoelectric (Piezolith 2300; Wolf, Knittlingen, Germany) shock-wave system. In nine healty volunteers, three therapeutically used intensities were applied in a randomized order with each lithotripter (MPL 9000: 16, 20, and 24 kV; Lithostar Plus: settings 5, 7, and 9; and Piezolith 2300: settings 2, 3, and 4). The subjects received nine series of 20 shock waves amounting to a total of 180 shock waves per session. The treatment was performed under clinical conditions, and no premedication was given. A visual analog scale and the McGill Pain Questionnaire were used for assessment of pain. In addition, somatosensory evoked potentials caused by shock-wave stimulation were recorded. Some of the volunteers were unable to bear the pain caused by the highest shock-wave intensity of the electrohydraulic (n = 3) and the electromagnetic system (n = 4). Estimates using the visual analogue scale showed increased pain sensations with increasing energy settings for each lithotripter. The amplitudes of the somatosensory evoked potentials became larger, and latencies shortened with increasing stimulus intensities (P less than 0.05). Subjective estimates by means of the visual analogue scale (P less than 0.01) as well as the McGill Pain Questionnaire (NS) and the somatosensory evoked potentials (P less than 0.05) showed that stimulation by the piezoelectric lithotripter was less painful than stimulation by the two other generators.

Adult↗
PubMed1992

Dose-proportional plasma levels of the analgesic flupirtine maleate in man. Application of a new HPLC assay.

Single oral doses of the non-opioid, centrally-acting analgesic flupirtine maleate (Katadolon, CAS 75507-68-5) were administered to healthy volunteers and the 2 h plasma levels determined with a new specific HPLC assay. 50, 100, 200, and 300 mg were ingested as the commercial capsules in a double-blind randomized cross-over design with time intervals of at least 6 d. Dose-proportionality was observed for the median 2 h plasma levels which is in agreement with dose-proportionality previously described for multiple-dose studies.

Aminopyridines↗
PubMed1991

The mucosal potential elicited by noxious chemical stimuli with CO2 in rats: is it a peripheral nociceptive event?

Negative mucosal potentials (NMPs) were recorded from the nasal respiratory mucosa in rats following retrograde stimulation with CO2 through a tube advanced to the nasopharynx. Local application of capsaicin (3 mg in 0.3 ml solvent, n = 5) and lidocaine (31 mg in 0.3 ml solvent, n = 5) eliminated the NMPs and cortical responses in the EEG. A quantitative reduction in NMPs was found following systemic pretreatment with capsaicin (cumulative dose, 200 mg/kg, n = 4), but not with guanethidine (50 mg/kg s.c., n = 4). Blood flow measurements and NMPs were obtained from the same recording position (n = 4). Onset of blood flow changes (1200-4800 ms) appeared significantly later than the onset of NMPs (120-500 ms). On the basis of these results a sensory neurogenic origin of the NMP is assumed.

Animals↗
PubMed1991

Changes in olfactory perception during the menstrual cycle.

The aim of the study was to find correlations between changes in olfactory sensitivity and the menstrual cycle. 14 young, healthy volunteers participated in the experiments. Subjects menstruated regularly and did not use oral contraceptives. Three odorants were investigated: phenylethyl alcohol, androstenone, and nicotine. Dilution series of the odorants were prepared, and presented to the subjects in order to determine the detection thresholds (triple forced choice). Additionally, the subjects' hedonic estimates of the odorants were measured, and mood states as well as hormonal levels of LH and estrogen were determined. Before the actual experiments started, subjects participated in three training sessions. One experiment was subdivided into 5 phases (two pre- and two postovulatory phases; one ovulatory phase). Only with regard to androstenone did trend analyses reveal a significant quadratic relationship between hedonic estimates and phases of the menstrual cycle, peaking at ovulation. Olfactory sensitivity was not significantly influenced by the menstrual cycle.

Adult↗
PubMed1991

Kallmann's syndrome and chemosensory evoked potentials.

Kallmann's syndrome is generally assessed by history and subjective tests of olfactory function. In this study three patients suffering from Kallmann's syndrome were investigated with more objective techniques, including the recording of chemosensory evoked potentials (CSEPs). After testing olfactory function by means of a simple odor identification test, anosmia was confirmed in only one patient, since the other two patients were able to distinguish between several odorants. However, investigations in which CSEPs were employed indicated that all three patients had complete loss of their olfaction as well as hypersensitivity of the trigeminal nerve. These findings prove the usefulness of CSEPs in clinical investigations of the sense of smell.

Adolescent↗
PubMed1991

Dose-related analgesic effects of flupirtine.

1. Flupirtine is a novel and, in all probability, centrally acting, analgesic. The present investigation was conducted in order to investigate dose-related effects of perorally administered flupirtine in man, with special regard to specifically analgesic actions, employing a model based on pain-related chemosomatosensory evoked potentials and subjective intensity estimates of painful stimuli. 2. Plasma concentrations of flupirtine measured 2 h after dosing linearly increased as a function of the administered dose. 3. It was possible to reproduce our own previously obtained results, which established the analgesic action of 200 mg flupirtine administered perorally. 4. Intensity estimates linearly decreased as a function of the administered dose, whereas chemosomatosensory evoked potential amplitudes non-linearly changed in relation to the administered dose. 5. In the spontaneous EEG, a dose-dependent increment in the power-spectra was observed, and this mainly in the alpha- and beta-range.

Administration, Oral↗
PubMed1990

Effects of pentazocine and acetylsalicylic acid on pain-rating, pain-related evoked potentials and vigilance in relationship to pharmacokinetic parameters.

Achieving objective and quantitative measurement of experimental pain in human volunteers and establishing the impact of drugs remains a difficult task. This problem may be overcome by employing a method which allows the simultaneous measurement of pain ratings elicited by standardized stimulation of the nasal mucosa by carbon dioxide, together with pain-related chemo-somatosensory evoked potentials (CSSEP) and vigilance. We assessed the effect of pentazocine and acetylsalicylic acid on these parameters in 14 human volunteers and related the effects to the pharmacokinetic parameters of the drugs measured at the same time. Pentazocine was found to reduce the pain ratings as well as the amplitudes of the pain-related evoked potentials and to increase their latencies. Vigilance (measured by EEG power spectra and performance of a tracking task) was also significantly reduced. These effects were observed during the distribution phase and the first period of the terminal elimination phase of the drug. Acetylsalicylic acid had no significant effects on pain ratings, but reduced the amplitudes of the event-related potentials when compared to placebo controls. At the same time a slight, but significant, effect on vigilance (reduced performance of the tracking task) was observed. These effects could not be related to the presence of unmetabolized acetylsalicylic acid in the plasma. They appeared at later times when only salicylic acid was left. It is concluded that chemical stimuli of sufficient intensity produce pain which may be suppressed by opioid analgesics such as pentazocine. The effect of acetylsalicylic acid on this experimental pain did not reach significance for all measured parameters under the experimental conditions chosen. The changes in vigilance and in the amplitudes of pain-related chemo-somatosensory evoked potentials indicated as yet unknown CNS-effects of this non-steroidal anti-inflammatory drug.

Adult↗
PubMed1989

Is there directional smelling?

The aim of the present study was to establish the crucial precondition for directional smelling, i.e. the ability of humans to discriminate between odorous stimuli perceived either from the right or from the left side. When the 'pure' odorants hydrogen sulphide or vanillin were used as stimulants localization was random. On the other hand stimulation with carbon dioxide or menthol yielded identification rates of more than 96%. These results established the fact that directional orientation, considering single momentary odorous sensations, can only be assumed, when the olfactory stimulants simultaneously excite the trigeminal somatosensory system.

Adult↗
PubMed1986

Cortical responses to painful CO2 stimulation of nasal mucosa; a magnetoencephalographic study in man.

Magnetic and electrical responses to CO2 stimulation of the nasal mucosa were recorded in 4 subjects. The magnetic responses peaked at 350-400 msec, coinciding with the negative vertex potential. The field pattern suggested neural activation in the upper bank of the sylvian fissure near the lateral end of the central sulcus, i.e., at or near SII. The results also suggest that this area contributes to the generation of the electrical vertex potential.

Adult↗
PubMed1986

The effects of analgesics on pain-related somatosensory evoked potentials.

Human cerebral evoked potentials can be employed to test the effectiveness of analgesics. In the present study, pain-related cortical responses were elicited by chemical stimulation of the nasal mucosa in combination with electrical stimulation of dental pulp. In alternating sequence, 16 series of 6 chemical and 6 electrical stimuli each were presented. Interstimulus and interseries intervals were 2 s and 50-60 s, respectively. Stimulus intensities were 54% carbon dioxide (v/v) and 4 dB over the electrical current threshold of 21-45 microA for noxious chemical and electrical stimulation, respectively. Four volunteers participated in the study. The EEG was recorded at 8 sites of the international 10-20 system. After each series of stimuli, the test subjects, using visual analogue scales, rated pain intensity relative to a single standard stimulus they had received initially. After running through the procedure once, without their noticing it, the subjects intravenously received 5 ml (2.5 g) metamizol or 5 ml 0.9% NaCl, which were slowly (over a period of 12 min) added to an infusion. The entire stimulation procedure was then repeated 10 min later. Whereas the evoked potentials clearly exhibited habituation effects due to stimulus repetition within a series, the latter were absent in the subjects' pain ratings. Despite the comparatively high i.v. dose of 2.5 g metamizol, pain ratings markedly different from those given under placebo were not observed. In contrast, potential amplitudes after metamizol administration exhibited a clear tendency towards smaller amplitudes in both types of stimulation. In addition, metamizol effects on pain rating could be demonstrated successfully by applying continual chemical stimulation.

Analgesics↗
PubMed1985

Gustatory evoked potentials in man.

Despite numerous attempts, a satisfactory method of recording gustatory evoked potentials (GEPs) had not been found as yet. This study reports a new stimulation technique by which taste receptors can be stimulated selectively. Gaseous chemical stimuli of an approximately rectangular concentration course were presented to 5 subjects. Acetic acid at different concentrations was used as the stimulant. The EEG was recorded from standard 10/20 positions referred to A1. Taste receptors were activated in a sufficiently synchronous manner to evoke summated slow wave potentials in the central nervous system. Concordant with other cortical evoked potentials, the vertex was the site of the most pronounced deviations of GEPs. Potential amplitudes increased and latencies decreased with rising concentrations. After application of the local anaesthetic tetracaine hydrochloride (10 mg) to the tongue, GEPs and taste sensations were eliminated. In one patient ageusia coinciding with irradiation therapy (36 Gy) was proved by the attenuation of the GEPs. Also GEPs to sweet (chloroform), salty (ammonium chloride) and bitter (thujone) taste sensations were recorded for the first time.

Acetates↗
PubMed1976

[Decrease of latency of auditory evoked potentials in humans practicing transcendental meditation (author's transl].

Slow cortical auditory responses were recorded from humans practicing transcendental meditation. The potentials were computated according to Fig. 1, and the latencies of the positive peaks P1 and P2 and of the negative peaks N1 and N2 were measured as well as the areas of the on-effect FON, of the off-effect FOFF and of the DC-shift FDC during the stimulus duration. Latencies for most of the initial peaks during TM as well as during normal consciousness were significantly shorter than in a control group in a dozing state or during normal consciousness (Table 1 and Fig. 2). Certain differences were also found in regard to other parameters such as amplitudes and areas of the auditory evoked response.

Acoustic Stimulation↗