Biomedical subjects

Heinrich Fruhstorfer

Publications and source records attributed to Heinrich Fruhstorfer.

4 recordsLinked to original sources

PubMed2003

The significance of A-delta and C fibres for the perception of synthetic heat.

Synthetic heat is a perception of strong, but not painful, heat arising when skin is stimulated by an alternating pattern of adjacent cold and warmth. This study examines the contribution of different classes of nerve fibres to this perception. In 40 subjects changes in synthetic heat and thermal perceptions were studied during a 30-min ischaemic nerve block in one reaction time, and one threshold determination task. Synthetic heat stimuli were described as hot or warm, but not as painful, and were preceded by a transient cold. Reaction times for synthetic heat stimuli did not differ from those for cold stimuli. Thresholds for synthetic heat and thermal stimuli were similar. During A fibre nerve block the perception of synthetic heat lost the cold component whereas the frequency of hot and warm descriptors did not change. The perception of cold stimuli changed, such that pure cold was replaced by dysaesthetic descriptors. Reaction times and thresholds for thermal and synthetic heat stimuli increased equally during the nerve block. It is concluded that the perception of synthetic heat most likely arises from the fusion of signals dependent on unmyelinated low threshold cold and warm receptors. It is not dependent on A-delta cold fibres, and a contribution of nociceptors is quite unlikely. The possibility of a psychological contribution at the perceptual level is discussed.

Adult↗

PubMed1986

The effects of thermal stimulation on clinical and experimental itch.

In order to substantiate accidental observations on the influence of skin temperature on itch, and to elucidate a possible involvement of thermoreceptors in itch generation, the effects of thermostimulation on clinical and experimental itch were studied. Eighteen patients with atopic dermatitis rated the intensity of spontaneous itch on one of their forearms before, during, and after its immersion in a waterbath of either 10 degrees C or 45 degrees C. In 40 normal subjects itch was elicited by histamine topically applied to a 7 cm2 skin area of the volar forearm. Before and after histamine application thermal thresholds were recorded. Then the skin area was heated or cooled at a rate of 0.5 degrees C/sec and itch intensity was continuously rated. Cooling abolished itch in all patients and in most of the normal subjects. Heating produced less clear effects: in two-thirds of both patients and normal subjects itch disappeared or was reduced whereas in the others itch was aggravated. Usually after the end of thermostimulation the opposite changes in itch intensity occurred. In the normal subjects thermal thresholds were not significantly influenced by histamine. Over a certain temperature range itch and thermal sensations could coexist as separate modalities. The results indicate that changes in skin temperature have a marked influence on itch intensity. Whereas cooling seems to act directly on the sensory receptors mediating itch, warm stimuli could have a central inhibitory effect. A direct role of thermoreceptors in the generation of itch is improbable.

Adult↗

PubMed1984

Thermal sensibility changes during ischemic nerve block.

Changes in perception of pure thermal stimuli delivered to the hand at threshold intensity were observed during ischemic nerve block in 27 healthy subjects in order to study the significance of unmyelinated cutaneous cold receptors for thermal sensibility. Paresthesias and an increasing feeling of numbness were followed by a sudden change in cold sensation which developed a clearly dysesthetic quality. When complete motor block was reached and no myelinated axon functions were left, cold stimuli were still clearly but abnormally perceived. Warm sensation was little affected during the whole course of nerve block. The results indicate that the information from unmyelinated low threshold cold receptors alone leads to a dysesthetic cold sensation which normally is suppressed by the activity of myelinated cold afferents. Obviously these receptors are not needed for the discrimination of minor cold stimuli but they seem to be essential for the perception of the first burning cold pain.

Adult↗

PubMed1983

Vascular participation in deep cold pain.

As the magnitude of cold pain probably depends on blood flow and thus on internal limb temperature, the activated nociceptors should be close to or within the walls of veins. This hypothesis was tested by injecting small quantities (20 ml) of cold saline into an empty vein of the hand in 16 subjects. Saline temperatures below 26 degrees C elicited pure cold sensations whereas temperatures below 20 degrees C evoked both cold and pain sensations. Pain was mainly described as deep and it tended to radiate along the veins. With saline of 5 degrees C the pain tolerance level of several subjects was reached. Pain always appeared after cold and it disappeared before or together with cold. The results can be explained on the basis of two types of vascular receptors: a sensitive specific cold receptor and a nociceptor with a threshold around 20 degrees C.

Adult↗