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Biomedical subjects

E R Perl

Publications and source records attributed to E R Perl.

65 records · Page 4Linked to original sources
PubMed1968

Myelinated afferent fibres innervating the primate skin and their response to noxious stimuli.

1. The functional characteristics of cutaneous receptors in the squirrel monkey were determined by recording discharges of single myelinated afferent fibres in peripheral nerves with micro-electrodes or from fine filaments prepared by dissection. One hundred and sixty-nine fibres of the posterior femoral cutaneous nerve and 209 of the superficial radial nerve with conduction velocities between 4 and 88 m/sec were classified according to the nature of the most effective stimulus, discharge characteristics, adaptation rate and organization of the receptive field.2. Twenty per cent of the fibres innervating either hairy or glabrous skin required strong mechanical stimuli for activation; thresholds ranged from moderate to overtly damaging pressures. This class showed little or no sensitivity to thermal changes including noxious heat. Their receptive fields consisted of numerous, mechanically-excitable points or spots. All such fibres gave higher impulse frequencies to noxious than to innocuous mechanical stimuli and a large fraction were considered to be nociceptors because they responded only to noxious deformation. The conduction velocities of nociceptors were distributed between 5 and 28 m/sec.3. All but a few of the other fibres encountered responded vigorously to innocuous stimuli and were readily identified as corresponding to one of the receptor types known to exist in either the primate or the cat. These sensitive receptors were systematically tested by intense cutaneous stimuli; their response to injurious stimuli always could be mimicked by innocuous ones.4. Therefore, in the primate a particular class of slowly-conducting myelinated fibres is partially responsible for signalling mechanically-induced cutaneous damage. The probable relation between such afferent fibres and certain kinds of cutaneous pain is explored.

Action Potentials↗
PubMed1967

Myelinated afferent fibres responding specifically to noxious stimulation of the skin.

1. The characteristics of receptors from the hairy skin of the hind limb of cat were studied by recording from single primary afferent fibres with fine micropipettes. The distinctive features of 513 fibres conducting under 51 m/sec are described.2. Seventy-four fibres conducting between 6 and 37 m/sec were classified as nociceptors because they responded only to damaging mechanical stimulation of the skin. These fibres responded maximally to pinching the skin with a serrated forceps or to cutting the skin. Noxious heat, noxious cold, acid applied to the receptive field and bradykinin injected into skin cuts did not evoke discharges from such receptors. Typically their receptive fields were 2-5 cm long by 1-2.5 cm wide and consisted of responsive spots (under 1 mm diameter) separated by unresponsive areas. There was a tendency for the most slowly conducting fibres so classified to be the least sensitive.3. Other afferent fibres had receptive fields similar to the nociceptors; however, they were excited by substantial but not noxious mechanical deformation. Their conduction velocities overlapped those of the nociceptors and extended upwards to 51 m/sec; the most rapidly conducting fibres tended to be the most sensitive to mechanical stimuli. These insensitive mechanoreceptors or moderate pressure receptors adapted more slowly than the nociceptors.4. The majority of fine myelinated axons originated from hair receptors and had conduction velocities concentrated between 14 and 22 m/sec.5. The possible relation of these observations to pain and reactions typical of pain is considered.

Action Potentials↗
PubMed1966

Amovement receptor of the small intestine.

1. The characteristics of a mechanoreceptor of the small intestinal region of the cat were studied by recording potentials from single afferent fibres in filaments dissected from mesenteric nerves. Forty-six fibres were examined in detail. Each of these was excited by light mechanical stimulation of the mesentery or small bowel, but none responded to sinusoidal vibration at frequencies above 100/sec. A ;spontaneous' discharge was regularly observed and it appeared to be related to peristaltic intestinal activity. On the other hand, non-propulsive motor contractions of the intestinal musculature were poorly correlated with discharge frequency.2. The region of maximal sensitivity of each fibre was determined by light pressure applied with a fine probe. Under these conditions the receptive field always resolved itself into 1-5 sensitive points (smaller than 1 mm in diameter). Each such point lay upon or immediately adjacent to a branch of the mesenteric artery supplying the area. Commonly, one or more sensitive spots were located at the place where a mesenteric artery entered the intestinal musculature. Localized pressure to one sensitive spot evoked a low frequency discharge (under 30/sec) which adapted within several seconds. A movement of the mesentery or the intestine distorting the region near one of the sensitive points regularly evoked a near maximal response. The dynamic phase of distension of the intestine by an intraluminal ballon also evoked a response. During inflation or deflation of the intestinal balloon, the frequency of discharge was positively correlated with both the rate of inflation and the pressure reached at the end of the dynamic phase. There was little relation between static distension and the discharge frequency.3. The conduction velocity of each afferent fibre was determined by electrical stimulation of its mesenteric nerve. The majority of the fibres studied had conduction velocities between 5 and 10 m/sec, the range being 2-21 m/sec. These figures were taken to indicate that the fibres were myelinated and of small diameter. Histological determination of myelinated fibre diameter in the mesenteric nerves from which the recordings were taken suggested that the numerical factor relating fibre diameter in mu to conduction velocity in m/sec was under 6.4. It was concluded that these receptors signalled movement of the intestine, regardless of its origin.

Animals↗