Characteristics, specificity, and efferent control of frog cutaneous cold receptors

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Abstract

Thermal stimulation of frog skin produces a discharge in afferents in the dorsocutaneous nerve. The characteristics of this response were examined with regard to static and dynamic sensitivity to thermal stimuli and to mechanical sensitivity. Frog cutaneous receptors responded only to cooling, with no response to warming through the same thermal range. The static temperature at which these receptors were maximally active was about 24° C for Rana pipiens and about 27° C for R. catesbiana. The dynamic sensitivity of frog cutaneous receptors was linearly related to both stimulus slope and magnitude; maximum dynamic sensitivity was between -90 and -120 impulses/°C.sec. Antidromic occlusion experiments demonstrated relative insensitivity of these receptors to tonic mechanical stimulation. Spike heights were linearly related to conduction velocities in the dorsocutaneous nerve; tonic mechanoreceptors had a mean spike height of 28.4 ± 0.6 μV and conduction velocities of about 6-8 m/sec, whereas these temperature sensitive receptors had spike heights of 15.3 ± 0.4 μV and conduction velocities of about 3-4 m/sec. Maximum dynamic sensitivity skin was increased following stimulation of the first or second sympathetic ganglion. This increase was both marked and progressive, reaching a maximal enhancement of about 150-160% control at a stimulus rate of 5 stimuli/train, each train delivered once every 5 sec. Static sensitivity of the cold receptors was also increased following sympathetic stimulation. This increased sensitivity was shown by both an increased discharge rate within the same thermal range and by a decreased temperature of maximum static sensitivity. Sympathetic modulation of dynamic thermal sensitivity was mimicked by epinephrine and norepinephrine in doses of 10-6-10-7 g/ml. Ephedrine, another adrenergic agonist, also mimicked the enhancement of cold receptors by sympathetic stimulation. Propranolol and phentolamine both blocked the enhancement of the response by sympathetic stimulation, but propranolol blocked the response of the receptor to thermal stimulation as well. Reserpine pre treatment blocked the effect of sympathetic stimulation on the cold response.

Original languageEnglish (US)
Pages (from-to)15-38
Number of pages24
JournalJournal of Physiology
Volume237
Issue number1
StatePublished - 1974
Externally publishedYes

Fingerprint

Anura
Hot Temperature
Skin
Propranolol
Temperature
Rana pipiens
Ephedrine
Adrenergic Agonists
Sympathetic Ganglia
Mechanoreceptors
Phentolamine
Reserpine
Epinephrine
Norepinephrine

ASJC Scopus subject areas

  • Physiology

Cite this

Characteristics, specificity, and efferent control of frog cutaneous cold receptors. / Spray, David C.

In: Journal of Physiology, Vol. 237, No. 1, 1974, p. 15-38.

Research output: Contribution to journalArticle

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abstract = "Thermal stimulation of frog skin produces a discharge in afferents in the dorsocutaneous nerve. The characteristics of this response were examined with regard to static and dynamic sensitivity to thermal stimuli and to mechanical sensitivity. Frog cutaneous receptors responded only to cooling, with no response to warming through the same thermal range. The static temperature at which these receptors were maximally active was about 24° C for Rana pipiens and about 27° C for R. catesbiana. The dynamic sensitivity of frog cutaneous receptors was linearly related to both stimulus slope and magnitude; maximum dynamic sensitivity was between -90 and -120 impulses/°C.sec. Antidromic occlusion experiments demonstrated relative insensitivity of these receptors to tonic mechanical stimulation. Spike heights were linearly related to conduction velocities in the dorsocutaneous nerve; tonic mechanoreceptors had a mean spike height of 28.4 ± 0.6 μV and conduction velocities of about 6-8 m/sec, whereas these temperature sensitive receptors had spike heights of 15.3 ± 0.4 μV and conduction velocities of about 3-4 m/sec. Maximum dynamic sensitivity skin was increased following stimulation of the first or second sympathetic ganglion. This increase was both marked and progressive, reaching a maximal enhancement of about 150-160{\%} control at a stimulus rate of 5 stimuli/train, each train delivered once every 5 sec. Static sensitivity of the cold receptors was also increased following sympathetic stimulation. This increased sensitivity was shown by both an increased discharge rate within the same thermal range and by a decreased temperature of maximum static sensitivity. Sympathetic modulation of dynamic thermal sensitivity was mimicked by epinephrine and norepinephrine in doses of 10-6-10-7 g/ml. Ephedrine, another adrenergic agonist, also mimicked the enhancement of cold receptors by sympathetic stimulation. Propranolol and phentolamine both blocked the enhancement of the response by sympathetic stimulation, but propranolol blocked the response of the receptor to thermal stimulation as well. Reserpine pre treatment blocked the effect of sympathetic stimulation on the cold response.",
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