A reversed action of the vagus on the mammalian heart / by H.H. Dale, P.P. Laidlaw, and C.T. Symons.

  • Dale, Henry H. (Henry Hallett), 1875-1968.
Date:
[1910?]
Catalogue details

Licence: Public Domain Mark

Credit: A reversed action of the vagus on the mammalian heart / by H.H. Dale, P.P. Laidlaw, and C.T. Symons. Source: Wellcome Collection.

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    impulses across the synaptic junction. This is in accordance with the accepted fact that changes in the time-relations of nerve-impulses occur normally only at synaptic junctions. It is further supported by the observation that, when the reversal phenomenon has been fully developed, pilocarpine still produces its normal cardio-inhibitor effect, as does also a further and larger injection of nicotine. This inhibitor effect of nicotine was particularly marked when tropine was the drug primarily used in producing the reversal phenomenon. The post¬ ganglionic neurones, therefore, and the peripheral mechanism with which they are connected, retain their normal responsiveness to such stimuli as affect them directly. Fig. 5. Cat. Urethane. 150 mgm. of tropine. Complete delayed inhibition succeeding stimulation of the left vagus. Coil at 12 cm. Time in seconds. II. Acceleration of the heart-beat by stimulation of the vagus during delayed inhibition. Turning to that phase of the phenomenon which leads us to describe it as a “ reversed ” vagus effect, namely the re-acceleration of the heart-beat when the stimulation of the vagus is renewed during a period of delayed inhibition, the first obvious possibility to be considered is that of mere spread of current on to the sympathetic accelerators. This can be excluded in several ways. (1) Stimulation at all points of the cervical vagus is equally effective in producing the acceleration. (2) The use of tripolar electrodes makes no difference. (3) Pinching the nerve peripherally to the electrodes prevents the acceleration. (4) In one experiment we exposed the stellate ganglion with its rami, the annulus, and the sympathetic cardiac branches. A stimulus,