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Title: The physiology of colour changes in the minnow (Phoxinus phoxinus) with particular reference to the pharmacology of the melanophore-controlling fibres
Author: Grove, David John
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1967
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Changes in state of melanophores in the minnow, Phoxinus phoxinus (L) -, which are known to be controlled by sympathetic paling fibres and pituitary paling hormone, were recorded macroscopically by comparison of the fish with standard grey papers. The effects of mammalian autonomic drugs on background adaptation were investigated by injections into intact, spinal sectioned and spinal nerve sectioned minnows. Adrenaline and noradrenaline, and to a lesser extent other sympathomimetic amines (ephedrine, tyramine, amphetamine, isoprenaline) were potent paling agents. Alpha-adrenergic blocking agents dispersed the melanophores. There was no evidence for antagonistic beta receptors. Hypotensive agents (reserpine, guanethidine, bretylium) abolished the nervously-coordinated background responses. Changes in potency of catecholamines after lesions in the chromatic tract, cocaine and chronic treatment with hypotensive drugs suggest that these amines stimulate directly and are closely related to the peripheral trans-mitter. Suppresion of the actions of tyramine and amphet-amine after cocaine and hypotensives implies that they act indirectly by displacing transmitter from an adrenergic store. Muscarinic stimulants possesed little, if any, darken-ing action on the minnow. Muscarinic blocks antagonized fast colour changes and atropine exerted pronounced darkening activity. Nicotinic blockade affected the shade of fish: hexamethonium prevented paling but nicotine was strongly sympathomimetic. It is concluded that aggregating fibres from the spinal cord pass to the sympathetic chain and cholinergic. their postganglionic counterparts are adrenergic and run in the spinal nerves. The adrenergic mediator (adrenaline, noradrenaline or dopamine) is stored at or near the nerve terminals and the indirect actions of sympathomimetic amines at this site are antagonized by cocaine, bretylium, reserpine and probably dibenamine. The adrenergic receptors are considered either as synergistic alpha and beta receptors or as primitive undifferentiated receptors"There is evidence for an antagonistic set of darkening fibres which accompany the paling fibres to the periphery but they cannot with certainty be said to be cholinergic.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physiology