Neural representation of cutaneous aftersensations by spinothalamic tract neurons.

Temporal summation of second pain and long-lasting tactile-evoked aftersensations are examples of sensory phenomenons that cannot be explained on the basis of responses of primary afferents. Two distinct classes of monkey spinothalamic tract neurons have responses to controlled natural stimuli that parallel and thus could account for the above phenomenons. One class, termed wide-dynamic-range, receives excitatory effects from sensitive mechanoreceptive afferents and from various nociceptive afferents including Adelta and C mechanothermal nociceptive afferents.

Ratio scales of sensory and affective verbal pain descriptors.

The results of two experiments show that ratio scales of sensory and affective verbal pain descriptors are valid, reliable and objective. In the first experiment, 16 subjects rated 15 sensory and 15 affective verbal pain descriptors by numerical magnitude estimation and by cross-modality matching to handgrip force. Ratio scales of sensory and affective verbal pain descriptors computed for two separate groups were highly correlated between the groups (sensory, r = 0.

Validity and sensitivity of ratio scales of sensory and affective verbal pain descriptors: manipulation of affect by diazepam.

The results of two experiments suggest that sensory and affective verbal descriptors provide a valid scaling method which discriminates between the sensory intensity and the affect, or unpleasantness, of electrocutaneous stimuli. Twenty-four subjects judged the sensory intensity and affect of noxious electrocutaneous stimuli by choosing verbal descriptors from randomized lists and by cross-modality matching to time duration and to handgrip force. The psychophysical functions for sensory intensity generated by the descriptor and the cross-modality functions for sensory intensity generated by the descriptor and the cross-modality methods are the same.

New methods of pain measurement and their application to pain control.

Recent pain research advances show promise in their application to the relief of acute and chronic clinical dental pain. Regional electroanalgesia, or transcutaneous electrical stimulation, has been used successfully in the treatment of pain associated with peripheral nerve injuries. Electrical stimulation of teeth also may prove useful as a pain control technique during operative dentistry procedures.

The pilo-Ruffini complex: a non-sinus hair and associated slowly-adapting mechanoreceptor in primate facial skin.

A spray-type of nerve ending identified as a Ruffini corpuscle closely associated with a non-sinus hair has been defined in terms of its histologic, ultrastructural and physiologic parameters. The hair and its associated mechanoreceptor, termed a pilo-Ruffini complex, responds as a slowly adapting (SA) mechanoreceptor, whereas most non-sinus hair-associated mechanoreceptors are rapidly adapting. Morphologically, the terminal nerve fibers branch repeatedly within a unique connective tissue matrix, and the neurite and associated connective tissue matrix forms a collar around the hair follicle.

Peripheral suppression of first pain and central summation of second pain evoked by noxious heat pulses.

Psychophysical experiments were carried out on 6 huma subjects to determine how first and second pain are influenced by peripheral receptor mechanisms and by central nervous system inhibitory and facilitatory mechanisms. For these experiments, brief natural painful stimuli delivered to the hand were a train of 4-8 constant waveform heat pulses generated by a contact thermode (peak temp. = 51-5% C).

Response of unmyelinated (C) polymodal nociceptors to thermal stimuli applied to monkey's face.

1. The response of C polymodal nociceptors to thermal and mechanical stimuli applied to the monkey's face was recorded extracellulary in the trigeminal ganglion in rhesus monkeys anesthetized with sodium pentobarbital. Conduction velocities, determined from electrical stimulation of receptive fields (RFs), were in the range for unmyelinated C fibers (mean=0.

Trigeminothalamic neurons in nucleus caudalis responsive to tactile, thermal, and nociceptive stimulation of monkey's face.

1. A total of 113 trigeminothalamic neurons and over 200 presumed interneurons of nucleus caudalis (0-5 mm below the obex) and subjacent reticular formation were studied in rhesus monkeys anesthetized with chloralose or nitrous oxide. Each cell was characterized in terms of its antidromic responses to stimulation of ventral posterior medial and/or posterior thalamic nuclei and to three types of stimuli applied to its receptive field: a) graded 5-s temperature shifts at a rate of 9 degrees C/s from 35 degrees C to final temperatures of 20-52 degrees C, generated by a contact thermode; b) graded intensities of electrical stimulation to determine the conduction velocities of converging primary afferent fiber populations; and c) mechanical stimulation ranging from light touch to pinch with serrated forceps.

Descending influences of periaqueductal gray matter and somatosensory cerebral cortex on neurones in trigeminal brain stem nuclei.

Single relay (to thalamus) and nonrelay neurones that responded to innocuous and/or noxious oral-facial stimuli were located in trigeminal brain stem nuclei oralis and caudalis. The responses of the cells and the digastric muscle to these stimuli were tested with conditioning stimulation of the periaqueductal gray matter (PGM) and somatosensory cerebral cortex in cats. A greater suppression of nociceptive responses with PGM stimulation was noted, and this effect may contribute to the profound analgesic action that has been reported to occur with PGM stimulation.

A peripheral "cold" fiber population responsive to innocuous and noxious thermal stimuli applied to monkey's face.

The activity of 134 cold fibers innervating the hairy skin of the face was recorded from fine dissected strands of the infraorbital nerve in rhesus monkeys anesthetized with sodium pentobarbital. A precisely controlled contact thermode was used to produce rapid temperature shifts of approximately 10 degrees C/s in the cooling and warming directions with a 20-60 degrees C range. Cold fiber receptive fields usually were single spots less than 300 mum in diameter.