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Title: A comparison between the pharmacological responsiveness of sensory nerve endings and sympathetic ganglion cells
Author: Watson, Philip J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1969
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The effects of a number of agonists, antagonists and local anaesthetics on electrical activity in fibres of the rabbit saphenous nerve in situ, and. on the surface potential of the isolated superior cervical ganglion of the rat have been studied. Acetylcholine, carbachol, methacholine, pilocarpine, Mcl A343, nicotine, tetramethylammonium, dimethylphenylpiperazinium, histamine, 5- hydroxytryptamine, bradykinin and angiotensin induced an afferent discharge in fibres of the rabbit saphenous nerve on intra- arterial injection into the skin. The same compounds depolarized the isolated . ganglion, although the rank orders of potency differed somewhat in the two preparations. The use of the appropriate agonists and. antagonists showed. that the cholinoceptive sites could be subdivided. into muscarinic and nicotinic receptors, the latter predominating in both tissues. Adrenaline and noradrenaline first augmented and then depressed. the acetylcholine -induced. discharge in the saphenous nerve; these effects were mediated via a- adrenoreceptors. Isoprenaline produced a prolonged small. increase in the acetylcholine -induced. discharge and this effect was mediated via ß- adrenoreceptors. In the isolated ganglion, adrenaline and. noradrenaline produced. a weak, a- receptormediated, hyperpolarization. Drugs possessing a nicotinic action gave rise to a secondary hyperpolarization of the ganglion cells which followed the initial depolarization on washing the tissue. Some evidence was obtained suggesting that this hyperpolarization was not a rebound phenomenon consequent upon the initial depolarization, but was due to the release of catecholamine within the ganglion. Drugs with a muscarinic action gave rise to a late post-washing depolarization which appeared to be mediated via muscarinic receptors. Guanethidine blocked. the action of acetylcholine on the saphenous nerve and. on the ganglion, but only in the former preparation did the effect resemble the adrenergic neurone blocking action of the drug in being reversed by d.examphetamine. No evidence was forthcoming to support the concept of the existence of a synaptic gap associated. with sensory endings: natural touch responses were still present at a time when drug - induced discharges had, been extinguished by antagonistic agents. A brief study was made of the effect of local anaesthetics and. drugs with local anaesthetic properties upon both preparations. It is suggested. that the rabbit saphenous nerve preparation may provide an additional means of assessing the potency and. durability of local anaesthetic agents. The results are discussed. in relation to the effects of the drugs on other non-myelinated neuronal membranes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available