Vasoactive intestinal polypeptide is likely to play a part in the vagal cardiac accelerator system. However, conclusive evidence for its role as the terminal transmitter in the VCA pathway will have to wait for the availability of a specific cardiac VIP receptor antagonist.

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In ten vagus nerves the effect of local cooling on the compound action potential was studied in the temperature range of 34 to 0 degrees C in spontaneously breathing, anaesthetized rabbits. The mean temperature at which the myelinated (A) fibres were completely blocked, was 10.2 +/- 2.4 degrees C (mean +/- S.D.). In nine nerves, local vagus cooling to 0 degrees C failed to block all non-myelinated (C) fibres. In one nerve, total blocking occurred at 2.0 degrees C. We conclude that in the rabbit, the earlier found increase in tonic activity of the diaphragm following lung inflation or deflation during bilateral local vagus cooling to a temperature between 8 and 0 degrees C is due to afferent impulses in vagal C fibres.

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The disappearance of the anticoagulant activity of a intravenously administered well-defined commercial heparin was followed in human and dogs utilizing a diluted activated partial thromboplastin time (Marder) and an anti-Xa-assay (Tin). The anticoagulant activity was followed after the injection of a large single dose. More accurate determination of the relation between heparin level and disappearance rate was achieved by continuous infusion with different heparin dosages. The anticoagulant effect was linearly related with dosage administered above a certain minimum threshold. This is in agreement with disappearance curves obtained after a single injection that can be described by the formula:(in which S represents the heparin activity, K1 and K2 represent constants and K3 is the integration constant). References: Marder, V. J.: A simple technique for the measurement of plasma heparin concentration during anticoagulant therapy. Thromb. Diath. Haemorrh. 24, 230–239, 1970.Yin, E. T., Wessler, S.: Plasma heparin: A unique, practical, submicrogram sensitive assay. J. Lab. Clin. Med. 81, 298-310, 1973.