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Carotid sinus baroreceptor reflexes and their interactions with trigeminal and respiratory stimuli in man, and their modification by sex, age, hypertension, antihypertensive therapy, alcohol and endogenous opioids

Collier, David John; (1992) Carotid sinus baroreceptor reflexes and their interactions with trigeminal and respiratory stimuli in man, and their modification by sex, age, hypertension, antihypertensive therapy, alcohol and endogenous opioids. Doctoral thesis (Ph.D), University of London, St. Bartholomew's Hospital Medical School. Green open access

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Abstract

The work in this thesis follows the use of the established neck suction technique for the assessment of carotid sinus baroreceptors in man and the development of a computer-based system for the analysis of responses to baroreceptor, trigeminal and respiratory stimuli. These methods have been used to study the carotid sinus baroreceptor reflexes, their interactions with trigeminal and respiratory stimuli, and their modification by gender, alcohol consumption, increasing age, essential hypertension and antihypertensive therapy. The role of endogenous opioids as putative neurotransmitters in these reflex pathways has been examined. The results obtained indicate that; 1) Endogenous opioids do not modulate carotid sinus baroreceptor reflexes and their interactions in normal man. 2) There was a difference in the extent of the linear portion of the carotid sinus baroreceptor heart rate reflex between closely age matched groups of young men and women. 3) The acute administration of alcohol reduced the sensitivity of the carotid sinus baroreceptor heart-rate reflex, but did not alter the response to cold facial stimuli, or the nature of the interaction of these (a simple linear summation of the effects of each applied separately). The effectiveness of respiratory stimuli in reducing vagal tone may have been reduced by alcohol. 4) The sensitivity of the carotid sinus baroreceptor reflex declined with increasing age, and with hypertension. This decline was significantly correlated with age, systolic, diastolic and arterial pulse pressure. 5) The response to trigeminal (cold facial) stimuli declined with age, but did not decline further in hypertension. Because the trigeminal and baroreceptor reflexes share a common efferent pathway, the vagus nerve, this is strong evidence for the preservation of the efferent pathway of the baroreceptor reflex in essential hypertension. The qualitative nature of the interaction between inspiration and the carotid sinus baroreceptor reflex was unchanged by hypertension. 6) The administration of two different antihypertensive agents, atenolol and lisinopril, whilst effective in reducing blood pressure, did not alter the sensitivity of the carotid sinus baroreceptor reflex, but the reflex was reset in each case to operate around a lower blood pressure, and with atenolol was also reset towards bradycardia. The response to cold facial stimuli, and the interaction with the carotid sinus baroreceptor heart- rate reflex were unchanged by therapy with either agent.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Carotid sinus baroreceptor reflexes and their interactions with trigeminal and respiratory stimuli in man, and their modification by sex, age, hypertension, antihypertensive therapy, alcohol and endogenous opioids
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10124910
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