The Innervation of Articular Blood Vessels

Khoshbaten, Ali (1989) The Innervation of Articular Blood Vessels. PhD thesis, University of Glasgow.

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Despite prevalence of inflammatory joint disease, at present little is known about the factors influencing articular blood flow. It was suggested that joint blood vessels in the dog are innervated by sympathetic efferent nerve fibres whose action is to constrict these vessels (Cobbold and Lewis 1956a). In other studies by Cobbold and Lewis (1956b), it was found that close intra-arterial injection of adrenaline and noradrenaline both produced vasoconstriction, but as to the types of adrenoceptors present on articular blood vessels, less is known. Dick and his colleagues concluded in their study on human that both alpha and beta adrenoceptors were present on knee joint blood vessels (Dick et al 1971). There would appear, however, to be little information known about the nervous control of articular blood vessels either in normal subject or in diseased synovial tissue e. g. rheumatoid arthritis. The object of this research was firstly to assess suitable in-vitro and in-vivo techniques to study knee joint blood vessels along with measurement of blood flow in the knee joint capsule and surrounding tissues such as muscle and bones in both rabbits and cats. Secondly, to perform a more extensive and quantitative investigation in order to characterize the types of receptors that are distributed on articular blood vessels and are important in regulation of blood flow (e. g. adrenoceptors, and purinoceptors), to identify the type(s) of nerves supplying joint blood vessels and their mediator(s) , and whether the endothelium plays a role in regulation of these vessels. Attempts were also made to study changes in nervous control and receptors on these blood vessels that might appear in the acute inflammatory joint disease. Lastly, results obtained in the cat and the rabbit were compared. Relative changes in blood flow were assessed by use of a perfused isolated knee preparation for the in-vitro studies, and both laser Doppler flowmetry and the microspheres technique were employed in the in-vivo experiments. Results from this investigation indicate that 1). Perfusion technique and laser Doppler flowmetry methods provide suitable means of assessing relative changes in articular blood flow in-vitro and in-vivo respectively. 2). Blood vessels in bone around the knee joint of the cat and the rabbit are innervated by presumed sympathetic vasoconstrictor fibres travelling in nerves supplying the joint. 3). Post-synaptic alpha1, alpha2 and pre-synaptic alpha2 adrenoceptors but not beta receptors are present on articular blood vessels. 4). Although P1, P2 purinergic receptors are present on vascular smooth muscle with P2 receptor also present on the endothelial layer, almost all of the data are consistent with the hypothesis that noradrenaline is the main neurotransmitter at knee joint blood vessels and produced vasoconstriction in response to articular nerve stimulation. It is also suggested that noradrenaline released from nerve ending affect mainly alpha1-adrenoceptors. 5). Afferent C fibres in articular nerves produce a dilator response to nerve stimulation and the mediator which is released from their terminals is most likely to be substance P. 6). Acute joint inflammation induced by kaolin increases the adrenoceptor sensitivity and influences those factors which normally regulate articular blood vessel calibre. The mechanisms that cause increase in sensitivity of adrenoceptors and the functional significance of this remain to be investigated. 7). The neurotransmitters released from nerves supplying the knee joint blood vessels and the receptors they act upon appear to be similar in both cat and rabbit. An interesting feature of these results is that, although the popliteal artery divides to give muscular and articular branches in close proximity to each other, the type of receptors on articular blood vessels are closer to that of superficial tissues such as skin than that of blood vessels supplying muscles. Thus, although both skeletal muscle and joints are considered to be deep structures, there is little homogeneity in distribution of receptors and types of innervation, which may reflect the differing function of these two vascular beds.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Medicine, Physiology
Date of Award: 1989
Depositing User: Enlighten Team
Unique ID: glathesis:1989-78030
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:43
Last Modified: 30 Jan 2020 15:43

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