Proceedings of the Association of Economic Biologists ordinary meeting held at 2.30 p.m. on May 13th, 1927, in the Imperial College of Science ... : discussion on plant alkaloids.

  • Association of Economic Biologists. Meeting (1927 : London, England)
Date:
[1927?]
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Credit: Proceedings of the Association of Economic Biologists ordinary meeting held at 2.30 p.m. on May 13th, 1927, in the Imperial College of Science ... : discussion on plant alkaloids. Source: Wellcome Collection.

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    administered, whereas the highest part of the cerebrum is put out of action first by hypnotics. Morphine and its derivative heroin are also valuable for their power of diminishing cough by depressing reflex excitability. 2. Hyoscine is also used for its depressant effect on the cerebrum. It is used in acute mania. Morphine is not much good in this connection—which is evidence in favour of the suggestion outlined in the last paragraph as to the action of morphine on the cerebrum. Hyoscine has the disadvantage of having certain peripheral effects on the pupil and the secretory glands similar to that of atropine. The peripheral action of atropine is due almost entirely to the laevo-hyoscyamine which it contains. The optical isomer dextro-hyoscyamine, the other constituent of atropine, has no such peripheral action and we are trying it at the moment as a substitute for hyoscine, but the results are not complete. B. Stimulants. The most important alkaloid used for stimulating the central nervous system generally is strychnine, which acts on all parts of the central nervous system, increasing the rapidity with which the organism responds to sensory stimuli and diminishing the latent period of reaction. It is almost confined to uses as a general tonic. One alkaloid has recently found a place in therapeutics because of its more or less selective activity on the part of the central nervous system which is responsible for the regulation of respiration, namely lobeline, which stimulates respiration in a very striking fashion. Apomorphine stimulates the vomiting centre. Caffeine also has a stimulating effect on the cerebrum. I have seen acute mania develop as a result of caffeine poisoning, and we all know its effect in the form of tea. (2) Drugs Acting on the Peripheral Nervous System. A. On the involuntary nervous system. The alimentary tract, the vascular system, the secreting glands, the sweat glands, the muscle of the eye and various other structures are under the control of two sets of nerve fibres which in general have opposing effects on these structures. One set of these fibres goes by the name of the sympathetic system, and the other by the name of the autonomic nerve system. (a) Drugs acting on the sympathetic system. Stimulants. The body itself produces an alkaloid which is concerned with the stimu¬ lation of the sympathetic system, namely adrenalin. There is only one alkaloid which has found extensive application in therapeutics for its effect on the central and sympathetic nervous system, and that is ephedrine, which has an action very similar to that of adrenalin. Its chemical formula is somewhat similar (see Fig. 1). It acts just like adrenalin by increasing the pulse rate, increasing the extent of the contraction of the heart, raising the blood pressure by causing contraction of the smooth muscles of the walls of the arterioles and it dilates the bronchioles. It is much more stable than adrenalin because of the absence of hydroxyl in the phenyl group. Larger doses have to be used of it than of adrenalin, but it can be administered by mouth whereas adrenalin is almost without action when taken by mouth probably because it is destroyed before it is absorbed. The drug comes from a species of Ephedra found in China and records of its use are said to be in existence dating from 5000 years ago.