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A Pertovaara

Publications and source records attributed to A Pertovaara.

125 records · Page 7Linked to original sources
PubMed1985

Influence of the rate of temperature change on thermal thresholds in man.

Thermal thresholds (cool, warm, heat, heat pain) were determined in four skin regions (cheek, glabrous skin of the hand, hairy forearm, leg) of eight healthy human subjects. The thermostimulator was composed of Peltier elements and three rates of continuous stimulation were used: 1.4, 2.4, and 3.9 degrees C/s. Warm, heat, and heat pain thresholds increased with increasing rate of temperature change, and the increase was of equal magnitude with these three thresholds. However, the effect of increasing stimulus rate on cool thresholds was nonsignificant. Similar results were obtained in all skin regions studied. It is suggested that liminal warm, heat, and heat pain sensations are mediated by afferent fibers with conduction velocities of the same range (C-fibers) whereas liminal cool sensations are signaled by faster conducting afferent fibers.

Adult↗
PubMed1985

The effect of tourniquet-induced ischemia on somatically evoked cerebral magnetic fields in man.

We recorded somatically evoked magnetic fields (SEFs) during tourniquet-induced ischemia in healthy humans. The subjective intensities of the stimuli decreased earlier and more clearly than the amplitudes of the SEF deflections peaking at 60-80 ms. Mixed nerve and sensory nerve responses behaved differently during ischemia. The results indicate that these SEF deflections are transmitted through thick myelinated fibers. Muscle afferents might contribute considerably to mixed nerve SEFs.

Adult↗
PubMed1985

Effect of tourniquet-induced ischemia on magnitude scaling of tactile stimuli applied to the human hand.

The effect of tourniquet-induced ischemia was tested on magnitude scaling of supraliminal tactile stimuli (single-cycle sine waves) applied to the human hand contra- or ipsilaterally to the cuff. Magnitude estimations were not influenced on the contralateral side. In the ischemic hand there was a reduction of magnitude estimates beginning 12 min. after inflation of the cuff, independent of the stimulus intensity. The results indicate that peripheral noxious stimulation does not produce a nonsegmental reduction of tactile sensitivity. Moreover, it is suggested that the thickest afferent mechanoreceptive fibers (A-beta) have a major role in the mediation of tactile signals both at liminal and supraliminal levels.

Adult↗
PubMed1984

The activation of unmyelinated or myelinated afferent fibers by brief infrared laser pulses varies with skin type.

Brief infrared laser pulses were applied to 3 different skin areas in man. Reaction times indicated that A delta-fibers were activated in the dorsal and volar skin of the finger whereas only C-fibers were activated in the hairy skin of the forearm. The qualitative sensations were in line with this interpretation. We conclude that the activation of unmyelinated or myelinated afferent fiber populations with brief laser pulses varies with skin type.

Adult↗
PubMed1984

The influence of exercise on dental pain thresholds and the release of stress hormones.

Different levels of exercise (50-200 W) were produced by a bicycle ergometer. In all six subjects the heart rate and blood pressure were increased with increasing work load. Dental pain thresholds tended to increase with increasing work load, too. Plasma ACTH levels were above the normal range during the whole experiment in all subjects, whereas plasma cortisol and prolactin levels were elevated only in one subject. Growth hormone levels had a tendency to elevation at 200 W. There was no correlation between the release of cortisol, prolactin or ACTH and the dental pain threshold elevation. However, there was significant correlation between the release of growth hormone and the dental pain threshold elevation. The results indicate that physical exercise at submaximal work loads is enough to produce a pain threshold elevation in some subjects, with a minor coactivation of stress mechanisms.

Adrenocorticotropic Hormone↗
PubMed1984

Vibrotactile thresholds in mechanoreceptive afferents innervating the foot pad of the cat. The importance of stimulus frequency and duration.

Vibrotactile thresholds were determined for non-Pacinian (SA and RA) and Pacinian (PC) mechanoreceptive units innervating the foot pad of the cat with vibratory stimuli of varying frequency (20, 80, and 240 Hz) and duration (100, 400, and 800 ms). Both the absolute (1 impulse/stimulus train) and the tuning (1 impulse/cycle) thresholds of SA and RA units were elevated and those of PC units were decreased as a function of increasing vibration frequency. PC units had the lowest thresholds at 80 and at 240 Hz whereas RA units had the lowest thresholds at 20 Hz. Larger atonal intervals (the range between the absolute and the tuning thresholds) were obtained for all unit types with increasing vibration frequency and PC units had the smallest atonal intervals at all frequencies. The absolute thresholds of all unit types were independent of stimulus duration. The tuning thresholds of SA and RA units were elevated with increasing stimulus duration whereas the tuning thresholds of PC units were independent of stimulus duration. Consequently, larger atonal intervals were obtained for RA and SA but not for PC units with increasing stimulus duration. The results indicate that there are both differences (effect of frequency) and similarities (effect of stimulus duration and the width of atonal intervals) in response characteristics of non-Pacinian mechanoreceptors innervating the hairy skin and the glabrous foot pad of the cat.

Adaptation, Physiological↗
PubMed1984

Effect of L-tryptophan supplementation on ischemic pain.

The synthesis of neurotransmitter amines in mammalian brain is known to respond to changes in precursor availability. After dietary manipulation including L-tryptophan supplementation 3 subjects out of 11 showed a significant reduction of experimentally induced ischemic pain. It is suggested that dietary manipulation aimed at an increase in central nervous system serotonin can alter pain perception in some individuals.

Adult↗
PubMed1983

Liminal and supraliminal response characteristics of mechanoreceptors of the hairy and foot pad skin of cat determined with short tactile pulses.

The liminal and supraliminal response characteristics of mechanoreceptive units innervating the hairy skin and glabrous foot pad of the cat were determined with single pulses of varying frequency (20, 60 and 150 Hz) in order to compare the characteristics of mechanoreceptors in cat and man. Altogether 172 units were tested. The units were divided into slowly adapting (s.a.) (I and II), rapidly adapting (r.a.) and pacinian (p.c.) units. No hairy skin p.c. units were encountered. The absolute thresholds and supraliminal responses of units innervating the hairy skin resembled those of human hairy skin mechanoreceptors, the s.a. II units having the lowest thresholds and both s.a. and r.a. units having lower thresholds as a function of increasing frequency of the pulse. The results suggest that on the hairy skin detection thresholds are based on activation of mainly s.a. II units, whereas the role of r.a. units is of importance for distinct touch and supraliminal sensations. S.a. units of foot pads were different if compared to s.a. units of human glabrous skin. R.a. and p.c. units in foot pads were similar to corresponding human units and the low detection and touch thresholds on the glabrous skin are explicable on the response properties of r.a. and p.c. units. According to the present study the results concerning response characteristics of cat hairy skin s.a. and r.a. units and cat glabrous skin r.a. and p.c. units can be applied to human psychophysical studies in the corresponding areas.

Animals↗
PubMed1982

Ischemic pain nonsegmentally produces a predominant reduction of pain and thermal sensitivity in man: a selective role for endogenous opioids.

Ischemic pain was produced by a blood pressure cuff placed to the arm of healthy human subjects for 15 min which produced a mean pain score of 59% (visual analogue scale). Ischemia induced a significant dental pain threshold elevation (mean 67%) and 2 mg of naloxone did not reduce it. Thermal sensitivity of the upper lip had a tendency to reduction during ischemia and 2 mg of naloxone reduced this effect. Tactile thresholds in the forehead or in the contralateral arm were not markedly elevated. Neither ACTH nor prolactin level in the plasma was related to the dental pain threshold elevation during ischemia. The findings of the present study suggest that ischemic pain nonsegmentally produces a predominant inhibition of responses to thin afferents. Endogenous opioids may markedly contribute to the reduction of thermal sensitivity induced by ischemia, but their contribution to dental pain threshold elevations seems to be less important. Stress or other adenohypophyseal mechanisms involving the release of ACTH or prolactin do not explain the effects of ischemia found in the present study.

Adrenocorticotropic Hormone↗
PubMed1982

Vibrotactile threshold elevation produced by high-frequency transcutaneous electrical nerve stimulation.

Vibrotactile thresholds for a 20Hz and a 150Hz stimulus were determined during high-frequency (100Hz) transcutaneous electrical nerve stimulation (TENS) of 13-minutes duration. TENS was applied either at a site proximal or distal to the probe of the vibrator at an intensity which was strong enough to elicit muscle activity. TENS applied at a distal site had no marked effect on vibrotactile thresholds either for a 20Hz or 150Hz stimulus. However, TENS applied at a proximal site caused a marked threshold elevation for both frequencies studied. Present results suggest that vibrotactile threshold elevation produced by high-frequency TENS is due to peripheral electrogenic blockade, presumably an antidromic invasion of vibration receptors.

Adult↗
PubMed1981

The influence of naloxone on dental pain threshold elevation produced by peripheral conditioning stimulation at high frequency.

The phasic dental pain threshold elevation produced by high-frequency transcutaneous electrical nerve stimulation (TENS) in healthy humans was not abolished by naloxone. A prolonged (20 min) high-frequency TENS did not cause any tonic pain threshold elevation. The results indicate that opioid-dependent systems have only a minor if any contribution to alleviation of experimental pain during high-frequency TENS.

Adult↗
PubMed1981

Vibrotactile thresholds in non-Pacinian mechanoreceptive afferents: the importance of temporal parameters.

Vibrotactile thresholds of non-Pacinian mechanoreceptive afferents (RA, SAI, SAII) were determined as a function of stimulus duration (100-800 ms) at three frequencies (20-240 Hz). Altogether 64 units innervating the hairy skin of the cat were tested. At all frequencies SAII units had the lowest thresholds whereas SAI units had the highest thresholds. At all frequencies and in all unit populations the absolute thresholds (1 impulse/stimulus train) were independent of stimulus duration, whereas the tuning thresholds (1 impulse/cycle) were elevated as a function of increasing stimulus duration. The present results suggest that the detection threshold decreases as a function of increasing stimulus duration are not based on peripheral properties of non-Pacinian mechanoreceptors.

Animals↗
PubMed1980

Experimental pain and transcutaneous electrical nerve stimulation at high frequency.

Transcutaneous electrical nerve stimulation (TENS) at high frequency and high intensity caused human pain threshold elevation for thermal stimuli only when thermal stimuli were applied at a site distal to the TENS electrodes. High-frequency TENS applied over the belly of m. biceps brachii did not cause a marked misestimation of elbow angle at any of the TENS intensities used. It is concluded that pain threshold elevation during high-frequency TENS is due to peripheral electrogenic blockade or fatigue of pain-mediating fibers. A minor effect of TENS on kinesthesia suggests a minor role of muscle afferents in mediating the effects of high-frequency TENS.

Adult↗
PubMed1979

Modification of human pain threshold by specific tactile receptors.

The effects of conditioning vibrotactile stimulation of particular tactile receptor groups on thresholds to painful electric stimuli were studied in seven healthy adults. Preferentially Pacinian afferents were activated with conditioning sinusoidal vibration of 240 Hz at 20 and 200 micrometers amplitudes and preferentially non-Pacinian tactile fibers were activated with conditioning sinusoidal vibration of 20 Hz at 200 and 400 micrometers amplitudes. None of the subjects showed pain threshold elevation during activation of non-Pacinian tactile fibers. However, 6 of the 7 subjects showed significant pain threshold elevation with conditioning vibration stimulus of 240 Hz at 200 micrometers amplitude, and 4 subjects showed significantly elevated pain thresholds with conditioning stimulus of 240 Hz at 20 micrometers amplitude. It is concluded that the activation of Pacinian afferents causes inhibition of pain conducting pathways.

Adult↗