The Journal of physiology
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The Journal of physiology · Sep 1980
Search for a cardiac nociceptor: stimulation by bradykinin of sympathetic afferent nerve endings in the heart of the cat.
1. We have examined the effect of bradykinin on impulse traffic in sympathetic afferent fibres from the heart, great vessels and pleura, and have attempted to identify cardiac nociceptors that on the basis of their functional characteristics might have a role in the initiation of cardiac pain. 2. In anaesthetized cats, we recorded afferent impulses from 'single-fibre' slips of the left 2nd--5th thoracic rami communicantes and associated chain, and selected fibres arising from endings in the heart, great vessels, pericardium and pleura. ⋯ It was a feature of the response of both mechanosensitive and chemosensitive endings. 8. Because of their responsiveness to changes in pressure and their sensitivity to light touch, the mechanosensitive endings appear to be unlikely to subserve a primarily nociceptive function, although they may be responsible for evoking some of the components of the pseudoaffective response. By contrast, the chemosensitive endings appear well fitted to act as cardiac nociceptors.
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The Journal of physiology · Sep 1980
The frequency selectivity of auditory nerve fibres and hair cells in the cochlea of the turtle.
1. The electrical responses of single auditory nerve fibres or cochlear hair cells were recorded in the isolated half-head of the turtle Pseudemys scripta elegans. Responses to sound stimuli presented to the tympanum could be recorded for at least 4 hr after isolation.2. ⋯ In the absence of deliberate sound stimulation, the hair cell voltage fluctuated continuously about its mean level. The principal frequency components in the noise were concentrated around the c.f. of the cell. The voltage noise in the hair cells showed no significant cross-correlation with sound pressure fluctuations at the tympanum.
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The Journal of physiology · Aug 1980
Cerebral blood flow and oxidative metabolism during hypoxia and asphyxia in the new-born calf and lamb.
1. The effects of hypoxia and asphyxia on cerebral blood flow and oxidative metabolism have been investigated in the calf and lamb under sodium pentobarbitone anaesthesia. 2. Cerebral blood flow was determined using a hydrogen clearance technique, and cerebral metabolism quantified by the simultaneous measurement of arteriocerebral venous concentration differences for oxygen, glucose and lactate. ⋯ Cerebral glucose uptake did not change, but cerebral oxygen consumption was markedly depressed, and the glucose-oxygen index increased. 6. In the lamb during normoxia, there was a linear correlation between cerebral blood flow and arterial PCO2 in the range 10-95 mmHg (r = 0.92; P < 0.001), with a slope of 1.74 ml. 100g-1 min-1 . mmHg Pa,CO2-1. Hypoxia did not significantly increase the fall in cerebral vascular resistance associated with a rise in Pa,CO2 from 34 to 56 mmHg.
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The Journal of physiology · Jan 1980
The control of sets of motoneurones by local interneurones in the locust.
1. A motoneurone innervating a muscle in a hind leg of a locust is controlled in a graded manner by many non-spiking, local interneurones. There is overlap and fractionation of control between these interneurones. ⋯ A single interneurone acting alone does not usually elicit the maximum output from one motoneurone, nor a complete piece of behaviour. A stronger contraction of a muscle and a more complete movement results from the action of groups of interneurones. 6. It is suggested that local interneurones, exerting graded control over motoneurones are a major element in the organization of motor patterns in the locust.