Reflex activity in the cervical and lumbar sympathetic trunk induced by unmyelinated somatic afferents

Schmidt, Robert F.; Weller, E.

doi:10.1016/0006-8993(70)90101-0

Cited by 59 publications

(14 citation statements)

References 17 publications

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“…Furthermore, in neurones of the spinal cord the axons of which ascend in the dorsolateral tract (Mendell & Wall, 1965;Mendell, 1966) especially in the spino-cervical tract (Gregor & Zimmermann, 1969; Gregor, 1971) and in the anterolateral tract (Manfredi & Castellucci, 1969;Manfredi, 1970) excitatory actions were described consequent upon volleys in cutaneous C fibres. Exceptionally prominent reflexes following C volleys occur in the sympathetic trunk (Schmidt & Weller, 1970), which probably account for the observation of profound cardiovascular reactions evoked by such stimuli (Ranson, 1921;Laporte & Montastruc, 1957).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of spinal neurones responding to cutaneous myelinated and unmyelinated fibres*

Gregor¹,

Zimmermann²

1972

The Journal of Physiology

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SUMMARY1. Spike discharges were recorded from neurones in the lumbar spinal cord in cats anaesthetized by barbiturate.2. The neurones were examined systematically for various physiological parameters and for their location. Especially the neurones situated in the dorsal horn were classified for the following parameters: mono-or polysynaptic linkage to myelinated afferents; type of natural stimuli which excited the neurones; depth from the cord surface; number of impulses discharged upon a cutaneous A fibre stimulus; steady-state discharge in the absence of intentional stimulation.3. All neurones were also tested as to whether or not they responded to volleys in cutaneous C fibres. Of 111 units which were activated by the A fibres in nerves from the hairy skin, 57 (= 51 %) responded to C volleys in those nerves too.4. By blocking conduction in the A fibres using polarizing currents it was shown that the responses to C fibre volleys were partially or totally suppressed by a preceding discharge of the neurone in response to an A volley. Using search stimuli which were suprathreshold for C fibres one cell out of 36 could be found which responded only to afferent volleys in C fibres.5. About half of all neurones were shown to be connected monosynaptically to cutaneous A fibres, as was judged from the synaptic delay. The other half were polysynaptically linked to the A fibres. Both monoand polysynaptic neurones were found in all layers of the dorsal horn.

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Section: Introductionmentioning

confidence: 99%

Characteristics of spinal neurones responding to cutaneous myelinated and unmyelinated fibres*

Gregor¹,

Zimmermann²

1972

The Journal of Physiology

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“…Activation of peripheral C fibres elicits somato-sympathetic reflexes and, consequently, induces changes in arterial blood pressure (Hunt, 1895;Ranson, 1921;Johansson, 1962;Coote & Perez-Gonzalez, 1970;Koizumi et al, 1970;Schmidt & Weller, 1970;Chung & Wurster, 1976). The somato-sympathetic reflex shows both temporal (Schmidt & Weller, 1970;Chung, Webber & Wurster, 1979) and spatial summation (Chung & Wurster, 1978).…”

Section: Discussionmentioning

confidence: 99%

“…The somato-sympathetic reflex shows both temporal (Schmidt & Weller, 1970;Chung, Webber & Wurster, 1979) and spatial summation (Chung & Wurster, 1978). In our study, the pressor response induced during high intensity stimulation of the ventral root displayed all the characteristics of the somato-sympathetic reflex.…”

Section: Discussionmentioning

confidence: 99%

“…Activation of afferent fibres from the contracting muscle seems to cause these responses, since the responses are abolished by paralyzing muscles or by sectioning the dorsal roots that innervate the contracting muscle. Because activation of peripheral non-myelinated afferent nerve fibres from skin, muscle, and viscera causes somato-and viscero-sympathetic reflexes (Hunt, 1895;Ranson, 1921;Johansson, 1962;Coote & Perez-Gonzalez, 1970;Koizumi, Collin, Kaufman & Brooks, 1970;Schmidt & Weller, 1970), stimulation of the ventral root, causing skeletal muscle contractions, could elicit pressor responses indirectly by way of somato-sympathetic reflexes. Another possible way to change blood pressure by ventral root stimulation would be by activating afferent fibres contained in the ventral root.…”

Section: Introductionmentioning

confidence: 99%

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Blood pressure response evoked by ventral root afferent fibres in the cat.

Chung

Kim

Shin

1986

The Journal of Physiology

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SUMMARY1. Systemic arterial blood pressure changes in response to stimulation of the distal stump of the cut spinal ventral root were investigated in anaesthetized, vagotomized, and carotid sinus-denervated cats.2. Low intensity electrical stimulation (< 20 T, where T is threshold intensity) of the ventral root caused a rise in blood pressure. This elevation was abolished by paralyzing the muscles with gallamine. This pressor response has been reported previously, and it is likely to be evoked by afferents excited by the contracting muscle.3. High intensity electrical stimulation (500 T) of the ventral root caused a second and marked pressor response. This was not affected by muscular paralysis or by cutting the sciatic nerve, but it was abolished by cutting the dorsal root.4. Threshold intensity for the second component of the pressor response was within the same range as the intensity needed for activation of C fibres in the ventral root, ranging between 200 T and 300 T. This response was graded with increasing stimulus intensity, and it showed both spatial and temporal summation.5. From the above results, we conclude that non-myelinated fibres in feline spinal ventral root course distally to the dorsal root ganglion and then enter the spinal cord via the dorsal root. Activation of these fibres results in a marked elevation of the systemic arterial blood pressure as in other somato-sympathetic reflexes induced by peripheral C fibre activation.

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“…There have been demonstrations of sympathetic reflex discharges induced by unmyelinated group IV (or C) somatic afferent volleys (the group IV-sympathetic reflex or C-reflex, as it may be called) [14,31,59] in addition to the early spinal and late supraspinal reflexes evoked by the myelinated afferents. The group IVsympathetic reflex usually requires a temporal facilitation of afferent volleys in anesthetized cat.…”

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confidence: 99%