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

Abstract

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.

Baroreflex responses to electrical stimulation of aortic depressor nerve in conscious SHR

“…Reflex responses to stimulation of the ADN in some species (e.g., cats, dogs) and the carotid sinus nerves are complex because of the presence of both baroreceptor and chemoreceptor afferent fibers (12,14). Fortunately, the rat ADN contains a relatively pure population of baroreceptor afferents (16 -18, 42).…”

Nonlinear Analysis of the Baroreceptor Reflex System

“…The performance of the baroreceptor reflex has been studied previously in preparations in which the feedback path was either intact 1 ' 2 or broken, 3 ' 4 and several models of blood pressure regulation have been proposed. 3 -"• 6 Physiological processes involved in the reflex control of blood pressure (such as sinus and aortic nerve activity, 7 ' 8 changes in cardiac output 9 and peripheral resistance, 9 ' 10 and renal and adrenal hormonal changes 11 ) have been studied individually. But complete, quantitative descriptions of the overall response and of the individual processes are lacking at present.…”

Depressor reflexes from medullated and non‐medullated fibres in the rabbit's aortic nerve

“…However, Douglas & Schaumann (1956) concluded from their experiments on the reflex effects of electrical stimulation of the cat's aortic nerve that this nerve must contain additional depressor afferents smaller than any barosensory fibres that have been recognized in it. These small afferents are not easily characterized in the cat because its aortic nerve is enclosed in the vagus throughout the greater part of its course.…”