Grundlagen der Atomphysik

Vagal reflexes appearing in asphyxia in rabbits at different ages

“…The heart beat was recorded by the electrical method already described [Bauer, 1938]. Blood pressure was recorded after the injection of heparin by cannulating the right femoral artery with a hypodermic needle connected with a membrane manometer, which was calibrated against a mercury manometer at the end of each experiment.…”

“…In older animals the initial blood pressure is higher, so that the depressor threshold would be-.exceeded earlier in asphyxia, accounting for the observed fact that the rise of heart rate brought about by the sympathetic effect is abolished progressively and finally disappears, being replaced by inhibition which appears still earlier in asphyxia and is finally present from the beginning. This state of affairs gives rise to type 5 [Bauer, 1938, Fig. 9], in which the vagal fall of heart rate appearing in type 2 [loc.…”

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IT was shown in a previous paper [Bauer, 1938] that asphyxiation gives rise to a vagal inhibition of the heart in rabbits, appearing in the form of two distinct manifestations, the first developing gradually after birth and attaining a maximum on the 11th day, and the second appearing after the 30th day and later combining with the first to produce the abrupt fall of heart rate consequent upon asphyxiation in adult rabbits. These vagal effects could arise as follows:

(a) the rise of blood pressure which occurs during asphyxia owing to the stimulation of the vasomotor centres by the accumulation of carbon dioxide [Mathison, 1911] may elicit the depressor reflex, or (b) the carotid sinus reflex, (c) the lack of oxygen or the accumulation of asphyxial products may cause a direct stimulation of the vagal centres in the medulla.

The extent to which these three factors are concerned at different ages is described in the present paper.

METHODS

The heart beat was recorded by the electrical method already described [Bauer, 1938].

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“…IT was shown in a previous paper [Bauer, 1938] that asphyxiation gives rise to a vagal inhibition of the heart in rabbits, appearing in the form of two distinct manifestations, the first developing gradually after birth and attaining a maximum on the 11th day, and the second appearing after the 30th day and later combining with the first to produce the abrupt fall of heart rate consequent upon asphyxiation in adult rabbits. These vagal effects could arise as follows:…”