The mechanism of the vasomotor reflexes produced by stimulating mammalian sensory nerves

Gordon, G.

doi:10.1113/jphysiol.1943.sp004019

Cited by 39 publications

(12 citation statements)

References 7 publications

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“…This demon strated that the response was refl ex in nature with the afferent limb located in the dorsal root. Other experiments have demonstrated that electrical activation of afferent fibers from muscle can elicit cardiac responses similar to those that accompany exercise, and these studies also suggest that the fibers involved are probably unmyelinated or small myelinated ones (48)(49)(50)(51). The changes even include an increase in left ventricular contractile state (50).…”

Section: Cardiovascular Control Mechanisms During Static Exercisementioning

confidence: 93%

Static (Isometric) Exercise and the Heart: Physiological and Clinical Considerations

Mitchell¹,

Wildenthal²

1974

Annu. Rev. Med.

164

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Section: Cardiovascular Control Mechanisms During Static Exercisementioning

confidence: 93%

Static (Isometric) Exercise and the Heart: Physiological and Clinical Considerations

Mitchell¹,

Wildenthal²

1974

Annu. Rev. Med.

164

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“…The enhancement of excitatory spinal sympathetic reflexes by strychnine (Langley, 1924) may also have an origin in such a mixed input, because strychnine is reported to depress specifically inhibitory processes (Bradley, Easton & Eccles, 1953;Kuno, 1957). Furthermore, mixed effects from given nerves might explain the type of response in more intact preparations where one frequency of stimulation resulted in an increase of blood pressure and a different stimulation frequency a decrease (Gordon, 1943). Finally, it is possible that inhibitory processes following the excitatory drive from a single afferent nerve are factors in the sudden ending of the preganglionic reflex discharge (Figs.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of a spinal sympathetic reflex

Beacham¹,

Perl²

1964

The Journal of Physiology

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In the spinal cat, a single volley in afferent fibres of one segment evokes a response in some preganglionic axons emerging from the same and from nearby segments. The maagnitude and latency of the refle'x response can be varied by gradation of the afferent volley; however, the fact that certain preganglionic fibres exhibiting background activity do not respond to the afferent volley indicates that not all of the neurones forming a given preganglionic ramus participate in the reflex. The initial description of this reflex (Beacham & Perl, 1964) left unanswered many questions about its functional organization, such as the conduction velocity of the responsible afferent fibres, the temporal recovery of reflex excitability and the effects produced by conditioning and tetanic afferent stimulation. The present study provides information on these points. From the results it is evident that, while the sympathetic reflex under consideration can be depressed or inhibited, facilitation of the response to a large afferent volley is rare. METHODSAll experiments were done on adult-cats made decapitate under ether anaesthesia by a spinal section at C-1 and by complete occlusion of the circulation to the head. After spinal section, anaesthesia was stopped and the preparations were maintained by positive-pressure artificial respiration: the respiratory rate and pressure were controlled to maintain the endtidal CO2 close to 5% (measured by a Beckman LB-1 infrared CO2 detector). Deep body temperatures were maintained between 36 and 38°C. Repeated injections of Flaxedil (gallamine triethiodide, American Cyanamid Company) were routinely used to give continued, total skeletal muscle paralysis. Five to 18 hr elapsed between spinal transection and the reported observations. Afferent volleys were initiated by stimulation of dorsal root filaments or segmental spinal nerves with 0-1 msec rectangular pulses. Stimulation of spinal nerves was arranged so that the stimulating cathode lay at least 10 mm distal to separation of the preganglionic bundle. Afferent activity was monitored by recording between an electrode placed on the dorsal root entrance zone and an indifferent electrode on adjacent bone.Recordings of preganglionic activity were made from axons in the segmental rami communicantes after removal of the connective tissue sheath, and often after splitting of the preganglionic bundle with the aid of a binocular microscope. If the reflex discharge observed consisted of activity in more than one or two elements, its magnitude was estimated from the area under the potential produced by the evoked response. In some instances, this was obtained from enlargements of photographs of the response, using a planimeter. Since the

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“…The phenomenon of 'reversal' in somatic nerve experiments has been ascribed to greater temporal summation of impulses at higher frequency or to the presence in these nerves of fibres of different qualities (see Gordon, 1943). The reversals seen on changing the frequencies of stimulation of the carotid sinus and aortic nerves seem to result from the different frequency/response characteristics of the depressor and pressor mechanisms associated with these nerves.…”

mentioning

confidence: 99%

A study of the depressor and pressor components of the cat's carotid sinus and aortic nerves using electrical stimuli of different intensities and frequencies

Douglas¹,

Schaumann²

1956

The Journal of Physiology

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Distension of the carotid sinus or the aortic arch causes a reflex fall in blood pressure. If records of electrical activity are taken from the carotid sinus or aortic nerves during the stimulus of distension many fibres of different size can be seen to fire. It is generally assumed that these impulses in diverse barosensory fibres are all concerned in the depressor reflex, 4nd that together they account fully for the reflex. Furthermore, it is held that the depressor effects of electrical stimulation of the carotid sinus and aortic nerves are to be attributed to excitation of barosensory fibres.Some idea of the function of different sized fibres can be obtained from experiments in which the nerves are stimulated electrically with carefully graded intensities of stimulus. Such an experiment was carried out by Douglas, Innes & Kosterlitz (1948 on the cat's carotid sinus nerve and yielded two curious findings: first, that little depressor function could be attributed to the large barosensory fibres so prominent in action potential records (and whose receptor behaviour has frequently been studied as typifying the barosensory depressor afferent); and secondly, that much of the depressor activity of this nerve seemed to be attributable to fibres smaller than the barosensory fibres that have been seen in action potential records. Moreover, Neil, Redwood & Schweitzer (1949 a, b) have observed that while stimulation of the cat's carotid sinus or aortic nerve after chloralose usually caused a rise in blood pressure, the effect sometimes became depressor when the pulse duration of the stimulus was increased. Although these workers do not make the point, this observation also suggests the presence of comparatively small depressor fibres in these nerves. * British Council Scholar.

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The mechanism of the vasomotor reflexes produced by stimulating mammalian sensory nerves

Cited by 39 publications

References 7 publications

Static (Isometric) Exercise and the Heart: Physiological and Clinical Considerations

Static (Isometric) Exercise and the Heart: Physiological and Clinical Considerations

Characteristics of a spinal sympathetic reflex

A study of the depressor and pressor components of the cat's carotid sinus and aortic nerves using electrical stimuli of different intensities and frequencies

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