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Biomedical subjects

E Mills

Publications and source records attributed to E Mills.

88 records · Page 5Linked to original sources
PubMed1969

Respiratory responses to electrical stimulation of the cervical sympathetic nerves in decerebrate, unanaesthetized cats.

1. The effects of respiration of electrical stimulation of the peripheral cut end of the cervical sympathetic nerve were studied in seventeen decerebrate, unanaesthetized cats.2. The tidal volume increased and the end-tidal CO(2) fell within 2-3 breaths after the onset of stimulation in fourteen cats.3. In three experiments tidal volume and respiratory rate fell during stimulation and increased above the control when the stimulus was interrupted.4. All respiratory responses to sympathetic stimulation were abolished after cutting the carotid sinus nerves and are attributed to activation of chemo- and baroreceptor afferents.5. With the carotid sinus nerves intact, respiratory responses could be eliminated completely only by cutting the post-ganglionic sympathetics that pass directly to the carotid body and the post-ganglionic sympathetics that join the glossopharyngeal nerves to course with the sinus nerves to the carotid bifurcation.6. Pentobarbitone (10 mg/kg) or chloralose (40 mg/kg) given intravenously depressed spontaneous ventilation and responses to sympathetic nerve stimulation.7. Stimulation changed blood pressure slightly in fourteen experiments; in ten it fell and in four it increased 10 mm Hg or less. After pentobarbitone or chloralose, stimulation elicited a pronounced pressor response.8. The results of the study indicate that activation of sympathetic pathways to the carotid body constitutes an effective stimulus to ventilation.

Animals↗
PubMed1968

Activity of aortic chemoreceptors during electrical stimulation of the stellate ganglion in the cat.

1. In anaesthetized cats, action potentials from aortic chemoreceptors were recorded during electrical stimulation of preganglionic sympathetic fibres to the decentralized right stellate ganglion. The rate of discharge in afferents in the ipsilateral but not in the contralateral aortic nerve increased when stimulus frequency was 4/sec or higher.2. The post-ganglionic fibres in the stimulated pathway originate in the right stellate ganglion. They leave the ganglion in the caudal limb of the ansa subclavia, and the results suggest that the ipsilateral aortic nerve and its branches distribute sympathetic fibres as well as afferents to aortic bodies.3. In contrast, the rate of discharge of chemoreceptor fibres in the contralateral aortic nerve fell as blood pressure increased during sympathetic stimulation. Sympathetic pathways to the aortic bodies can maintain or increase chemoreceptor discharge during hypertension elicited by sympathetic activation.

Journal Article↗
PubMed1967

Centrally evoked sympathetic discharge: a functional study of medullary vasomotor areas.

1. The medulla oblongata was stimulated electrically in decerebrate cats following bilateral vagotomy. Changes in splanchnic nerve discharge evoked by stimulation of pressor and depressor areas in the medulla are correlated with changes in arterial pressure. An interaction of baroreceptor afferents with the efferent sympathetic system at the level of the medulla and/or spinal cord is demonstrated. Evidence is presented which suggests that it is possible to alter activity selectively in a given division (splanchnic) of the sympathetic outflow.2. Evoked responses were categorized as follows:(a) Sustained splanchnic activation; an immediate increase in total splanchnic activity occurred with only a small, gradual decline in activity during the stimulation period. Mild stimulation (150-200 muA) raised systolic pressure by 60-80 mm Hg and stronger stimulation (300-400 muA) increased pressure by 100-150 mm Hg. When comparable pressor responses were elicited from points on either side of the mid line, splanchnic excitation was greater with homolateral stimulation (left side).(b) Unsustained splanchnic activation; an immediate increase in activity occurred which declined sharply as systolic pressure rose by 60-100 mm Hg during stimulation. Such a decline was attributed to the influence of baroreceptor afferents. Thus, if previous carotid occlusion was maintained during stimulation, the decline in activity was minimized although the pressor response increased. It is suggested that the structures yielding unsustained responses differ from those yielding sustained responses in their functional relation with the baroreceptor afferents.(c) Reduced splanchnic discharge during direct medullary stimulation; a partial or complete inhibition of splanchnic activity was obtained, which was sometimes accompanied by a 20-40 mm Hg reduction in systolic pressure. However, the direction and magnitude of the systemic pressure change were not as consistently related to the splanchnic response as they were during activation. Even if splanchnic efferent activity were elevated by carotid occlusion, stimulation still reduced discharge.

Animals↗
PubMedDate not supplied

Ontogeny of neural and non-neural contributions to arterial blood pressure in spontaneously hypertensive rats.

Arterial blood pressure was measured directly by cannulation in anesthetized spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats on postnatal Days 1, 5, 9, 20, 42, and 82-86. The time course for development of the following variables was established: resting diastolic and basal (after ganglionic blockade) pressure, the neural contribution to resting pressure (resting minus basal pressure), vascular reactivity to a noradrenergic agonist, methoxamine, and to endogenous sympathetic nerve terminal norepinephrine released by tyramine (maximum pressor response and ED50) and resting and basal heart rate. Resting diastolic pressure was higher in SHR compared to WKY by 24 hours after birth. In both strains, the increase in resting diastolic pressure with age was interrupted by a plateau period (Days 5-9 in SHR; Days 9-20 in WKY). Juxtaposition of the development curves was such that the interstrain differences in pressure were statistically significant in all periods studied except Days 5 and 9. Both basal and neurally mediated components of resting diastolic blood pressure were elevated in SHR compared to WKY. The magnitude of the interstrain difference in basal pressure remained constant during development while the magnitude of the neurally mediated component showed accelerated development through 42 days of age. Reactivity to methoxamine and tyramine was higher in SHR, but the magnitude of the difference did not change with age. Cardiac sympathetic tone was higher in SHR than WKY, but did not account for the increased resting diastolic pressure in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗