Effects of bilateral vagal cold block on vasopressin in conscious dogs

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Abstract
Bilateral vagal cold block was used to interrupt afferent nerve traffic in the cervical vagi and thus to determine the tonic inhibitory influence of vagal afferents on plasma arginine vasopressin (AVP) concentrations in the conscious dog. Experiments were performed in conscious aortic baroreceptor-denervated dogs with carotid baroreflexes intact or with sinoaortic denervation. In the presence of intact carotid baroreflexes (n = 11) vagal cold block significantly increased arterial pressure (99 .+-. 5 to 120 .+-. 8 mmHg), heart rate (98 .+-. 2 to 168 .+-. 11 beats/min) and AVP (2.9 .+-. 0.6 to 6.7 .+-. 1.3 .mu.U/ml). Chronic sinoaortic denervation did not significantly alter plasma AVP (4.4 .+-. 1.0 .mu.U/ml). Vagal cold block in these totally denervated animals caused a significantly greater increase in arterial pressure (116 .+-. 7 to 167 .+-. 7 mmHg) and plasma AVP (4.4 .+-. 1 to 33.4 .+-. 4.8 .mu.U/ml) compared with the responses observed in dogs with intact carotid baroreflexes. These results indicate that vagal afferent nerves exert a significant tonic inhibitory influence on the secretion of AVP in the conscious aortic baroreceptor-denervated dogs as well as in dogs with sinoaortic denervation.